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1985 EPRlIllE Geothermal Conference and Workshop

1985 Segunda Conferencia IIEIEPRI Sobre Programas de Geotermia

Authors’ Papers

June 25-28, 1985 Hyat t I slandia Hote I San Diego, California

CONTENTS CONFERENCE PAPERS SESSION.1 :

CONVENE CONFERENCE

Geothermal Energy i n t h e U n i t e d S t a t e s (Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n ) B a r t o n W . Shackel f o r d Geothermal Energy i n Mexico H e c t o r Alonso ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Geothermal Proqrams a t E P R I (Paper U n a v a i l a b l e a t Time o f Publ i c a t i o n ) h a i n Spencer Geothermal Proqrams a t I I E Pablo Mulas, David Nieva, J . Hernandez ( E n q l i s h T r a n s l a t i o n f o l l o w s Paper) U.S.

Department o f Energy P e r s p e c t i v e (Paper U n a v a i l a b l e a t Time o f Publ c a t i o n ) ( Ron Toms)

SESSION 2:

GEOTHERMAL POWER PLANT E X P E R I E N C E

I n i t i a l O p e r a t i n g R e s u l t s - - B l u n d e l l Geothermal 20 MW S i n g l e F l a s h P l a n t Dale R. Brown The F i v e U n i t s o f Cerro P r i e t o I (Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n ) Fernan do Lede zma S a l t o n Sea 1 0 MWe S i n g l e F l a s h P l a n t (Paper U n a v i i l a b l e a t Time o f P u b l i c a t i o n ) E l g i n Moss O p e r a t i o n o f S u r f a c e Equipment f o r Recovery o f Geothermal F l u i d s a t Cerro P r i e t o I A1 f r e d o Manon, F r a n c i s c o Bermejo, Pedro Perez ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) The HGP-A G e n e r a t o r F a c i l i t y R e s e r v o i r C h a r a c t e r l s t i c s and O p e r a t i n g H i s t o r y Dona1 d Thomas E f f e c t s o f H i g h Noncondensi b l e Gas Loads on Geothermal S u r f a c e Condensers--A Case Study Mary E . Matteson, Greg L . S t a r n e s O p e r a t i o n o f t h e M o b i l e U n i t s o f Los A z u f r e s L u i s Ortega P i e r r e s ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Design, S t a r t - u p and O p e r a t i o n o f SMUDGE0 #1 P . V . Kleinhans, D. L . P r i d e a u x S p e c i f i c a t i o n s f o r Development o f 5 MWe Power P l a n t s i n Mexico (Paper U n a v a i l a b l e a t Time o f Publ i c a t i o n ) A1 b e r t o P1 auchu SESSION 3:

RESEARCH & R E S E R V O I R ANALYSES

Geothermal E x p l o r a t i o n A c t i v i t i e s A n t o n i o Razo M o n t i e l ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) E x p l o r a t o r y D r i l l i n g a t Cos0 Geothermal F i e l d , C a l i f o r n i a (Paper U n a v a i l a b l e a t Time o f Pub1 i c a t i o n ) Murray Gardner, S u b i r Sanyal, R o b e r t B r i f f e t t Geothermal R e s e r v o i r Assessment A c t i v i t i e s i n Mexico Rafael Mol i n a r ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) E x p l o r a t i o n 4 Flow T e s t i n g a t Meager Creek, B r i t i s h Columbia (Paper U n a v a i l a b l e a t Time o f Publ i c a t i o n ) Joe Stauder Development o f t h e Los A z u f r e s Geothermal F i e l d Ramon Reyes Suarez ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper)

Geothermal Assessment i n t h e B o n n e v i l l e Power A d m i n i s t r a t i o n S e r v i c e Area Doug1as See1 y M u l t i d i s c i p l i n a r y S t u d i e s on t h e Geothermal F i e l d o f L O A~ z u f r e s

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David Nieva, Eduardo I g l e s i a s , V i c t o r A r e l l a n o , E n r i q u e C o n t r e r a s , A r t u o Gonzalez, Ramon Reyes ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Radon a s a Tool f o r R e s e r v o i r Assessment Lewis Semprini and Paul K r u g e r Overview o f Actual Knowledge o f t h e Heat Source i n Los Humeros Surendra Pal Verma ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Geothermal Development a t The Geysers (Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n ) SESSION 4 :

GEOTHERMAL POWER PLANT DEVELOPMENT

Economics o f Well head Versus C e n t r a l Power P l a n t s Gerard0 H i r i a r t S t a r t u p & T e s t i n g o f Heber B i n a r y P l a n t - - A n Update N e i l G. Solomon, R i c h a r d F. A l l e n E n g i n e e r i n g o f F i e l d I n s t a l l a t i o n s o f Geothermal Power P l a n t s Ranul fo G u t i e r r e x Rami r e z ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) C u r r e n t S t a t u s o f E n g i n e e r i n g , C o n s t r u c t i o n , and S t a r t - u p o f t h e Heber Double-Flash Geothermal Power P l a n t R. F. W i l l e t t , J. A. B i c k e r s t a f f e , L. B. Haag B i n a r y Cycl e S t u d i e s E n r i que R o d r i go Na j a r ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) N o r t h e r n Nevada Geothermal Developments and t h e 9 MWe Power P l a n t a t D e s e r t Peak W i l l i a m E. B l o c k l e y , W i l l i a m C. Ganser B a s i c C o n s i d e r a t i o n s on I n c r u s t a t i o n s i n t h e Desiqn and O p e r a t i o n o f G e o t h e r m o e l e c t r i c Power P1 a n t s Roberto Hurtadq, Fel i c i a n o Damian, F r a n c i s c o Bermejo ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Pesign, C o n s t r u c t i o n and O p e r a t i o n s o f t h e Mammoth Geothermal Power P l a n t s R i c h a r d G. Campbell and Ben H o l t SESSION 5 :

RESULTS FROM RESEARCH PROJECTS

R e s u l t s o f F i e l d T e s t i n g o f Process f o r Removing H2S b y Condensing and Re-Evaporating Geothermal Steam a t Cerro P r i e t o Raul Angulo, L u i s Lam, J a v i e r Gonzalex, y Pablo Mulas ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) D e m o n s t r a t i o n o f Geothermal S c a l e C o n t r o l U s i n g a F l a s h C r y s t a l l i z e r John R. Brugman and Doublas R. Brown Lessons Learned on B i n a r y Power Systems (Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n ) John B i q q e r Underqround P i p i n q f o r T r a n s p o r t o f Geothermal F1 u i d s M a r i o A. T e l l o de Meneses I t u r e n R e s u l t s f r o m t h e Geothermal C h e m i s t r y Subproqram: Mary McLearn

Trace Elements i n Geothermal Systems

Use o f Computerized Systems f o r t h e D e c i s i o n Making Process i n Geothermal Energy G u i l l e r m o Rodriguez O., I g n a c i o Sarmina 0. ( E n q l i s h T r a n s l a t i o n f o l l o w s Paper) R e s u l t s f r o m W e l l head Development P r o j e c t s Evan Hughes

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--

--

Research on E l u i d i z e d - B e d Heat Exchangers J . S i q u e i r o s , C. L. Heard, H . Pernandez ( E n g l i s h T r a n s l a t i o n f o l l o w s Peper) Bottomwell T e s t i n g o f Geothermal Cements G u i l l e r m o B a r r o s o and Manuel Morales ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) SESSION 6 :

PANEL DISCUSSIONS

F i e l d Development The Need f o r a Geothermal Database ( E n g l i s h T r a n s l a t i o n ) A r t u r o Gonzal ez S a l a z a r ( E n g l i s h T r a n s l a t i o n f o l l o w s Paper) Worl d w i de Geo t herma 1 Development R. DiPippo

GEOTHERMAL ENERGY I N THE U N I T E D STATES

B a r t o n W . Shackel f o r d

Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n

ACTUALES PERSPECTIVAS DE DESARROLLO DE LA GEOTERMIA EN MEXICO

ING. HECTOR ALONSO ESPINOSA Comisi6n Federal de Electricidad Morelia, Michoacsn.

R E S U M E N

Tomando como fecha llmite marzo de 1 9 8 5 , se indica la situaci6n presente de la geotermia en Mexico en relaci6n a las otras fuentes de energfa. En retrospectiva se hace una breve historia de lo que ha sido la exploraci6n y las actividades principales que en este tema se realizan actualmente. Se presentael potencial geot6rmico del pals dividido en reservas probadas, probables y posibles. Se detalla la cantidad de mdquinas geotermicas actualmen te instaladas y su potencia normal. Se presenta el pro-grama de expansi6n de la geotermia para 10s pr6ximos 15 afios indicando lo que se planea invertir en centrales y en plantas m6viles a contrapresi6n. Sobre estas Gltimas se explican 10s planes de inte-gracidn que s e tienen para fabricarlas casi por completo en el pals y el atractivo que representan desde el punto de vista econBmico y de exploracidn de un campo. Final-mente se indican algunos de 10s estudios que se estdn rea lizando sobre comportamiento de 10s fluidos geotermicos y aprovechamiento integral de 10s componentes de la salmuera.

ACTUALES PERSPECTIVAS D E DESARROLLO DE LA G E O T E R M I A EN M E X I C O

ING. HECTOR ALONSO ESPINOSA Comisi6n Federal de Electricidad Wrelia, Yichoach.

RESUMEN Tomando como fecha llmite marzo de 1985 s c comenta la situaci6n presente de 1z geotermia en M6xico en relaci6n a las otras fuentes de energla. En retros pectiva se hace una breve historia de lo que ha sido la exploraci6n y las actividades principales que en este tema se realizan actualmente. Se presenta el potencial geot6rmico del pals dividi do en reservas probadas, probables y pg sitles. Se detalla la cantidad de mdcruinas geotkrmicas actualmente instaladas y su potencia nominal. Se presenta el programa de expansi6n de la geoter-mia para 10s pr6ximos 15 afios indicando lo que se planea invertir en centrales y en plantas m6viles a contrapresi6n. Sobre estas Gltimas se explican 10s pla nes de integraci6n que se tienen para fabricarlas casi por completo en el pals y el atractivo que representan desde el punto de vista econ6mico y de explora-ci6n de un campo. Finalmente se indican algunos de 10s estudios que se est% realizando sobre comportamiento de 10s fluidos geot6rmicos y aprovechamiento integral de 10s componentes de la salmuera. INTRODUCCION Examinando las fuentes de generzi6n de energfa el6ctrica que se tenfan a m zo de 1985 y que se indican en la tabla siguiente: Termoelgctrica Hidroelgctrica Carboelgctrica Turbogas Ciclo combinado Getermoelgctrica

9 475 MW

Total

20 000 MW

6 500 MW 600 MW 1 800 MW 1 200 Mw

425 MW

Se aprecia que la geotermia, aunque crezca a ritmos acelerados estard por mucho tiempo a la zaga en cuanto a las fuentes tradicionales. Sin embargo, si se lleva a cab0 el plan esperado para -

10s pr6ximos aiios se llegard a1 afio 2000 con mas de 2000 MW lo que en t6rminos ab solutos serd una gran contribuci6n a la diversificaci6n de energ6ticos primarios Ademds de esta contribuci6nr la geoter-mia est5 sirviendo para desarrollar tecnologlas mexicanas en cuanto a produc--ci6n de vapor y fabricaci6n de equipo en el pals lo que seguramente redundard en beneficio de la independencia tecnol6gica en dreas estratggicas que se persigue Creemos que estamos viviendo en nuestros dlas solamente el inicio de la explota-ci6n del subsuelo para generar electrici dad. Mas adelante aparecerdn 10s ciclos binarios para campos de baja entalpfa y luego, quizd la fuente mds prometedora, la perforaci6n a grandes profundidades para aprovechamiento del calor magmdtico y de rocas calientes secas. Por el momento, en esta breve presey! taci6n me referir6 a las actividades con cretas que se han realizado en NExico y las perspectivas razonablemente alcanzables para 10s pr6ximos quince aiios.

EXPLORACION En PI6xico 10s primeros estudios para el aprovechamiento de la energla geotgrmica se inician a1 principio de la d6cada de 10s cincuenta, recabando informaci6n de las manifestaciones termales sg perficiales conocidas. Con esto, se logr6 establecer la existencia de mas de 60 dreas con manantiales de alta tempera tura y escapes de vapor. De este modo, se seleccion6 la zona de Path6 en el estado de Hidalgo, mds por su cercanla a la Ciudad de Pl6xico, centro de un elevado consumo de energla, que en base a sus caracterlsticas geotgr micas. Se efectuaron all€ varias perforacig nes obtenigndose siempre una mezcla de g qua y vapor de baja entalpla y produc-ci6n pobre, lo que limit6 el desarrollo del campo. A pesar de esto, se instal6 en esta zona la primera planta geotermoelgctrica del pals, generando solo 600 IQ?.

La importancia de Path6 radica en el hecho de haber sido la primera zona geo tgrmica desarrollada en M6xico, que pefl miti6 la preparacidn de t6cnicos mexica nos y la demostraci6n de la factibili-dad de esta tecnologfa de explotaci6n.

I

CERRO R E T O

Con estos resultados se decidid iniciar estudios preliminares de explora-ci6n en otras dreas del pals, comenzando en Los Negritos e Ixtidn de 10s Hervores en Michoacdn y en Cerro Prieto, Baja California. En este Gltimo campo,debido a sus ma yores perspectivas,se concentraron 10s esfuerzos y recursos. Las investigaciones iniciales permitieron determinar la existencia de un gran potencial geot6rmico als3cenado en el subsuelo, lo que se comprob6 a1 obtenerse desde las primeras perforaciones profundas algunas de las presiones y temperaturas mds altas logradas en ningGn otro ca PO.

-2

En 1963 se co perforaci6n del primer pozo geot6rmico en el campo de Cerro Prieto, existiendo a la fecha mds de 150 pozos perforados por lo que este yacimiento ha pasado a ser el segundo mds grande del mundo. Se encuen-tra situado sobre roca sedimentaria recibiendo la aportacidn dc calor por un levantamiento del magma en el subsuelo debido a pequefios desplazamientos de las placas tectdnicas que en ese lugar se intersectan.

7

El 6xito alcanzado en este campo se debe principalmente a que se ha podido comprobar con bastante certeza la existencia de una gran extensi6n de drea ca liente con abundante recarga hidrdulica y la confiquracibn bastante homoq6nea

que presenta el subsuelo.

Y PRINCIPALES CAMPOS GEOTERMICOS DE MEXICO

FIGURA

1

El conocimiento actual delterritoric de acuerdo a la intensidad con que se han realizado las exploraciones hasta la fecha ha permitido clasificar las re servas del pals de la manera siguiente: 1 ) Rebehwub phabudub - Representan

la potencia que se puede instalar asegu rando una operacidn contfnua de 20 afios basados en la certidumbre obtenida de haber realizado perforacio-nes de exploracibn y explotacidn teni6ndose ademds 1k shulaci6r, mi 6rics del yacimiento.

2 ) Rebetrwub p t r v b u b L e h - Son aquellas en

que mediante estudios geol6gicos, geoquEmicos y geoffsicos se ha podido cuantificar de manera aproximada el volumen y energfa tgrmica alniacenada e n el yacimiento.

- A s f se califican aquellas que se pueden estimar examL nando 10s inventarios de las manifes taciones t6rmicas superficiales.

3 ) ReAetrvub p a b i b L e n

POTENCIAL GEOTERMICO Con base en 10s resultados de las z g nas geotsrmicas descritas, se inici6 a nivel nacional el inventario de focos termales con el objeto de contar por una parte con elementos para programar las prioridades de desarrollo de campos geotgrmicos de acuerdo a s u potencial y a las regiones de demanda del pals y pa ra tener adembs, aunque de manera general, conocimiento de las reservas de vc por para el futuro. Est0 ha hecho que en 10s Gltimos afios se hayan invertido cantidades significativas en explora-ci6n. En la fig. 1 se indica la localizaci6n de 10s principales campos geot6r micos del pals.

De acuerdo a 10s estudios mds reciefl tes, se concluye que las reservas geo-tgrmicas de la RepGblica Mexicana de acuerdo con la Fig. 2 son: Probadas Probables Posibles

1340 MW 4600 MW 6 0 0 0 MW

Las reservas probadas corresponden bdsicamente a 10s tres campos actual-mente en desarrollo:

Cerro Prieto L . o s Azufres Los Humeros

Unidad Unidad Unidad Unidad Unidad

Cerro Prieto I

1

2 3 4

37.5 blw 37.5 Mw 37.5 Mw 37.5

m

5

30.0 Mw

Cerro Prieto I1

Unidad 1 Unidad 2

110.0 M w 110.0 b 5 l

Cerro Prieto I11

Unidad 1 Unidad 2

110.0 bW 110.0 Mw

mo en la Primave actuales campos en desarrollo. Y las posibles, correz?cnden a una estimacidn de 10s 35U rocos terma-

les que se conocen en la RepCtblica.

Ids

Azufres

Plantas ~ v i l e s 5 x 5 Mw

TABL8A RESERVAS GEOTERMICAS DE LA REPUBLICA MEXICANA

1

PROGRAMA DE EXPANSION Considerando el potencial de reservas y la necesidad de incorporar un vg lumen creciente de potencia geotermo-elgctrica a la red nacional se han pro gramado las instalaciones siguientes:

FIGUFU

2

POTENCIA INSTALADA Actualmente el aprovechamiento de la energca geot6rmica en el pals se en cuentra principalmente concentrada en el campo Cerro Prieto que contar6 a fi nales del presente afio con una potencia instalada de 6 2 0 000 KW. Adicional mente se tienen instalados hasta la fg cha 5 turbogeneradores portdtiles de 5 MW cada uno en el campo geot6rmico Los Azufres. Con esto se tendrd una potenci.2. i nnt.-l,-?a(;e 6 4 5 XW ,de ,:.cuerdo a la tabla 1, que colocard P Mexico como el tercer pars con va:m7- potencia geotermoelectrica instalada.

En Cerro Prieto, adem6s de 10s casi 6 2 0 MW instalados, se tienen conside rados para 1992 una potencia adicional de 220 MW suministrada por cuatro plantas de 5 5 MW cada una. Lo que representa un total de 840 MW pa ra este campo. perforaciones exploratorias recientes realizadas a1.N E del campo, mas a116 de ejido Nuevo ~ e 6 nhandemostra do que la extensi6n del yacimiento es mucho mayor que lo que original-mente se habfa estimado. Para no pecar de demasiado optimistas todavla no queremos dar cifras sobre la potencia adicional que se tendrla. Esperaremos que se concluyan las pruebas con modelos matem6ticos de simulaci6n y la perforacidn en 10s pozos exploratorios programada para dar CL fras confiables. 2 ) Para Los Azufres donde se cuenta actualmente con 5 turbogeneradores en

operacibn, desde noviembre de 1982 se contempld la construcci6n de una placta de 5 0 MW en el sector llamado Tejamaniles que deberd entrar en ope racidn a finales de 1986. Para 1 9 8 7 deberdn entrar en operaci6n 7 plan-tas mdviles de 5 MW cada una, ademds de 2 plantas de 5 5 MW correspondientes a Azufres I y I1 planeadas para

finales de 1 9 8 8 y 1 9 8 9 respectiva-mente. La construccibn de Azufres I11 de 55 MW se deber5 iniciar a me diados de 1 9 9 0 , luego de que hayan transcurrido unos 1 8 meses de eva-luaci6n basados en la historia de produccih que se ganard con la ope raci6n de Azufres I y 11. El programa de expansi6n para 10s campos Cerro Prieto y Azufres se esque matiza en la Fig. 3

2MW 500

I

2000

I 5'X

3) En el cas0 de Los Humeros, en vista de 10s resultados de 10s cuatro po-

zos perforados, se ha decidido instalar tres unic!ades de 5 MW a con--trapresibn para medidados de 1 9 8 7 . Ademds se ha programado la instalaci6n de dos plantas de 55 MW para 1 9 9 0 y 1 9 9 1 respectivamente.

\

De acuerdo a la programacibn que se ha descrito y tomando en cuenta un crg cimiento anual sostenido del 15% puede preverse para fines de siglo una poten cia de aproximadamente 2 440 MW en que gran parte de esta potencia estard constitulda por plantas m6viles, como ,se muestra en la Fig. 4. Lo anterior representa un ahorro de 35 millones de barrilesde wmbusk6leo cada afio que serla el equivalente de suministrar la misma potencia con plantas termoelCc-/ tricas. .

85

95

90

2 000 AN0

POTENCIA INSTALADA AL A i 0 2000

FIGURA

4

I

CONCEPT0 DE PLANTA MOVIL Uno de 10s logros inportantes que se han establecido paia el aprovechamiento del recurso geotgrmico es el empleo de turbogeneradores de 5 PliW de descarga ag mosfgrica y que se instalan a boca d e pozo.

b

PROGRAMA DE EXPANSION PARA ENERGIA GEOTERMICA In

In X

t

> n

MW

0

9 0 9 4 343 ~

-

I 10 n

X

1992 1985 1984 1983

FIGURA

1982 1986 1987 1988 1989 1992

3

Estas plantas se han considerado como una solucibn favorable especialmente si se emplean como unidades para la eva luacidn del yacimiento a1 extraer permg nentemente vapor desde puntos estratggi cos del campo, para analizar su evolu-ci6n, con la ventaja de que mientras se realiza esta prueba, se est5 recuperando el monto de la inversibn. Una caracterlstica importante de estas plantas-son su movilidad que en caso de fallar prematuramente el pozo o el yacimiento, en pocas semanas el equi PO se puede trasladar completo a otro pozo. Estas plantas portdtiles pueden instalarse tambign en forma permanente co-

mo unidades a contrapresi6n en aquellos casos en que: a) El contenido de gases incondensables del pozo sea muy elevado. b) Que la reserva sea muy pequefia como para justificar el disefio econdmico de una planta, como es el cas0 de Tres Vfrgenes en Baja California Sur, donde en un plazo muy corto se pueden instalar plantas portdtiles a boca de pozo para reemplazar la generaci6n que actualmente se reali za con plantas diesel. c) Que se requiera de una generaci6n temporal mientras se completa la efi ploraci6n del campo y la ccnstrucci6n de la central. El arreglo tfpico de una planta m6vi1 de este tip0 puede verse en la Fig. 5.

LINEA DE EXCEDENCI A \ -\

';I SECADOR

ELECTRIC0

fm VAPOR

SILENCIADOR

PRODUCT0

-.

REINYECTOR

PRREGLO TlPlCO DE UNA PLANTA MOVIL A CONTRAPRESION

FIGURA

5

El empleo de plantas portdtiles reviste actualmente un gran inter5s no solamente por las soluciones tecnicas que representa sino tambign porque serd un medio que contribuird a lograr el desarrollo de nuestras propias cap2 cidades tecnol6gicas. Recientemente se ha convocado a un concurso nacional para la compra de 10 unidades m6viles de 5 MW cuya fabrica-

ci6n contempla un programa creciente de integraci6n nacional para terminar con un 80% de fabricaci6n en el pals para la d6cima unidad. PROGRAMA

DE ESTUDIOS

Como resultado de la creciente actividad en el campo de la geotermia, la bcsqueda de una utilizaci6n mas racional y eficiente del recurso ha motivado la realizaci6n de diversos estudios. En la conduccidn de fluidos geot6rmi cos, se ha ganado gran experiencia en el conocjmiento del comportamiento del flujo bifdsico en vaporductos. En pozos con contenidos elevados de sales, la precipitaci6n de sflice es i" tensa tal como ocurre en Cerro Prieto. Se han realizado diversos experimentos y pruebas para conocer a fondo 10s mecg nismos que controlan la precipitaci6n y as4 realizar disefios mds seguros y econ6micos

Una de las grandes preocupaciones ha sido siempre el entendimiento de 10s fg ndmenos de corrosi6n y cuyas particularidades cambian de campo a campo, por lo cual, se han realizado extensos est2 dios en esta drea, tanto en Cerro Prieto como en Los Azufres. En la actualidad se ensaya con gran intergs la aplicacibn de tscnicas moder nas de toma de decisiones con incertidumbre en 10s proyectos geotermoelGctrL cos para incorporarlas a las evaluaciones de inversiones que rutinariamente se realizan. Aih cuando no se contempla todavfa la aplicacidn de plantas de ciclo bin2 rio en el pals ya se han iniciado diver sos experimentos encaminados a conocer con suficiente certeza la aplicabilidad de estos sistemas. En lo particularfresulta interesante el ensayo de un siste ma de ciclo binario con aqua desmineralizada en el secundario aplicable en salmueras con un alto contenido de ga-ses incondensables. Con la terminaci6n de la construccidn del vas0 evaporador para la recuperaci6n de cloruro de potasio en Cerro Prieto en que se estima una producci6n de -aproximadamente 100 000 ton a1 ario de esta sal, se ha iniciado el aprovechamiento comercial no el6ctrico de 10s recursos geot6rmicos en el pals. En la Fig. 6 se esquematiza el arreglo para

una planta de este tipo.

RECUPERACION DEL CLORURO DE POTASIO DE SALMUERA GEOTERMICA

FIGURA

CONCLUSIONES

LA

6

Estamos poniendo 6nfasis en abaratar 10s costos de la generacibn de energla

El ritmo sostenido de exploraci6n qeotgrmica que se ha logrado mantener en 10s Gltimos aiios, ha permitido aumentar las reservar probadas y hace prever que el crecimiento a raz6n de 1 5 % anual es una predicci6n conservadg ra.

Los aspectos mbs relevantes del futuro qeotgrmico en M6xico se podrlan expresar en dos hitos que destacan sobre el resto. Ellos son, la comprobaci6n de que el yacimiento de Cerro Prieto es bastante mbs extenso de lo que hasta hace un par de afios se sabla y que en campos geot6rmicos de estructura volcbnica complicada la instala-ci6n de plantas a contrapresi6n ubicadas a boca de pozo es una soluci6n ecg n6mica y sequra con el atractivo adicional de ser equipo sencillo que se puede fabricar en gran parte en el pals.

Tenemos ya programado, tal comose ha indicado en el. comienzo de este artfcg lo 2 2 0 MW adicionales para Cerro Prieto, 2 5 0 MW en L o s Azufres y 1 2 5 en Humeros. Se continuan las explorac'iones en La Primavera y otros puntos prometedores en 10s estados de Nayarit y Michoa c5n.

elgctrica con base en la geotgrmica, en mejorar las tgcnicas para localizaci6n de pozos y en el aprovechamiento de desechos geot6rmicos para usos no elSc-tricos.

CURRENT PERSPECTIVES ON THE DEVELOPMENT OF GEOTHERMICS I N MEXICO

BY H e c t o r Alonso E s p i n o s a Comision F e d e r a l d e E l e c t r i c i d a d M o r e l i a , Michoacan

SUMMARY Taking March 1985 a s t h e l i m i t , h e r e a r e some comments on t h e p r e s e n t s i t u a t i o n of g e o t h e r m i c s i n Mexico, i n r e l a t i o n t o t h e o t h e r s o u r c e s o f e n e r g y .

A

b r i e f h i s t o r y i s g i v e n of e x p l o r a t i o n and t h e p r i n c i p a l a c t i v i t i e s c u r r e n t l y u n d e r

I

way i n t h i s a r e a .

The p r e s e n t g e o t h e r m a l p o t e n t i a l o f t h e c o u n t r y i s shown,

d i v i d e d i n t o p r o v e n , p r o b a b l e , and p o s s i b l e r e s e r v e s .

The amount of g e o t h e r m a l

machinery c u r r e n t l y i n s t a l l e d and i t s nominal power a r e g i v e n .

I

The g e o t h e r m a l

e x p a n s i o n progam i s p r e s e n t e d , f o r t h e n e x t 15 y e a r s , i n d i c a t e d what i s t o be i n v e s t e d i n power p l a n t s and p o r t a b l e back p r e s s u r e u n i t s .

The p l a n s f o r t h e

a l m o s t complete m a n u f a c t u r e o f t h e l a t t e r w i t h i n t h e c o u n t r y a r e e x p l a i n e d , as

w e l l as t h e a d v a n t a g e of t h i s from t h e p o i n t of view o f economics and f i e l d exploration.

F i n a l l y , some s t u d i e s a r e mentioned t h a t a r e b e i n g done on t h e

b e h a v i o r of g e o t h e r m a l f l u i d s and : t h e - - f a € l - - u s e a of t h e components o f t h e b r i n e .

INTRODUCTION

Examining t h e s o u r c e s o f g e n e r a t i o n o f e l e c t r i c a l e n e r g y as o f March 1985, and which a r e i n d i c a t e d i n t h e f o l l o w i n g T a b l e : Thermoelectric

9 , 4 7 5 Mw

Hydroelectric

6,500 MW

Carboe l e c t r i c

600 MW

Tur bog a s

1 , 8 0 0 MW

Combined c y c l e

1 , 2 0 0 MW

Geothermoelectric

425 MW Total

20,000

;"M

w e s e e t h a t g e o t h e r m i c s , a l t h o u g h growing a t f a s t r a t e s , w i l l f o r a l o n g t i m e l a g behind t h e c o n v e n t i o n a l s o u r c e s .

N e v e r t h e l e s s , i f ? t t h e e x p e c t e d p l a n f o r t h e next

few y e a r s i s implemented, we w i l l r e a c h t h e y e a r 2 , 0 0 0 w i t h more t h a n 2,000 MW,

which in absolute terms will be a great contribution to the diversification of primary energy sources, Besides this contribution, geothermics is serving to develop Mexican technology in regard to steam production and the manufacture of equipment in the country, which will surely result in the benefit of technological independence in strategic areas.

We believe that today we are seeing only the

beginning of the use of the subsoil for generating electricity.

Further on, we

will look at the binary cycles for low enthalpy fields and then, perhaps the most promising source, drilling to great depths in order to m e the magmatic heat from dry hot rock. For the moment, in this brief presentation I will refer to the concrete activities carried out in Mexico, and to the reasonably achkevable goals for the next 15 years.

EXPLORATION In Mexico the first studies for the use of geothermal energy were started at the beginning of the 1950's, by gathering information on known surface thermal manifestations.

With this is was possible to establish the existence of more than

60 areas with high-bemperature hot springs and steam discharges.

In this way, the Pathe zone in the state of Hidalgo was chosen, more for its proximity to Mexico City, a center of high energy consumption, than for its geothermal characteristics. Some drilling was done there, obtaining a mix of wate and steam of low enthalpy and poor production, which limited the development of the field.

In

spite of this, the first geothermoelectric plant in the country was installed there, generating only 600 KW. The importance of Pathe is rooted in the fact that it was the first geothermal zone developed in Mexico, which permitted the training of Mexican technicians and the demonstration of the feasibility of this technology. With these results it was decided to begin preliminary studies on exploration in other areas of the country, beginning in Los Negritos and Ixtlan de 10s Hervores in Michoacan and Cerro Prieto, Baja California. In the latter field, due to its great possibilities, efforts and resources were concentrated, The initial research determined the existence of great geothermal potential stored in the subsoil, which was verified when, from the first deep bores some pressures and temperatures were encountered that were higher than in any other field.

I n 1963 t h e d r i l l i n g o f t h e f i r s t g e o t h e r m a l w e l l began a t t h e C e r r o P r i e t o field.

There a r e now more t h a n 150 d r i l l e d w e l l s , making t h i s r e s e r v o i r t h e

second l a r g e s t i n t h e w o r l d .

I t i s l o c a t e d on s e d i m e n t a r y r o c k t h a t r e c e i v e s an

i n f l o w o f h e a t from a r i s e i n t h e magma1 i n t h e s u b s o i l , due t o s m a l l d i s p l a c e m e n t s of t h e t e c t o n i c p l a t e s t h a t i n t e r s e c t i n t h i s a r e a . The s u c c e s s a c h i e v e d i n t h i s f i e l d i s due m a i n l y t o t h e f a c t t h a t i t w a s p o s s i b l e t o v e r i f y w i t h enough c e r t i t u d e t h e e x i s t e n c e o f a wide h o t area w i t h abundant h y d r a u l i c r e c h a r g e and t h e s u f f i c i e n t l y homogeneous c o n f i g u r a t i o n of the subsbil.

GEOTHERWL POTENTIAL Based on t h e r e s u l t s from t h e g e o t h e r m a l zones m e n t i o n e d , a n i n v e n t o r y o f t h e r m a l c e n t e r s w a s i n i t i a t e d on t h e n a t i o n a l l e v e l i n o r d e r t o f i n d t h e d a t a f o r p l a n n i n g t h e p r i o r i t i e s of development of t h e g e o t h e r m a l f i e l d s a c c o r d i n g t o t h e i r p o t e n t i a l and t h e areas o f demand of t h e c o u n t r y ; and a l s o , i n a g e n e r a l way, t o o b t a i n i n f o r m a t i o n on s t e a m r e s e r v e s f o r t h e f u t u r e .

T h i s w a s done i n

t h e l a s t few y e a r s and s i g n i f i c a n t amounts were i n v e s t e d i n e x p l o r a t i o n .

Fig. 1

shows t h e l o c a t i o n s of t h e p r i n c i p a l g e o t h e r m a l f i e l d s i n t h e c o u n t r y .

Y Fig. 1 M e x i c o ' s P r i n c i p a l Geothermal F i e l d s

P r e s e n t knowledge of t h e t e r r i t o r y a c c o r d i n g t o t h e i n t e n s i t y o f e x p l o r a t i o n t o d a t e h a s p e r m i t t e d c l a s s i f i c a t i o n of t h e c o u n t r y ' s r e s e r v e s a s f o l l o w s :

1)

Proven R e s e r v e s

-

They r e p r e s e n t t h e power t h a n can be i n s t a l l e d t o e n s u r e

o o n t i n u o u s o p e r a t i o n f o r 20 y e a r s , based on t h e c e r t i t u d e o f e x p l o r a t o r y b o r e s and u s e , a s w e l l as n u m e r i c a l s i m u l a t i o n of t h e r e s e r v o i r .

2)

Probable Reserves

-

Those where by means of geological, geochemical, and

geophydical studies it has been possible to quantify approximately the volume and thermal energy stored in the reservoir.

3)

Possible Reserves

7

Those that it is possible to estimate by examining the

inventory of superficial thermal manifestations. According to the most recent studies, it has been concluded that the geothermal reserves of Mexico, according to Fig. 2 , are: Proven

1,340 MW

Probable

4,600 MW

Possible

6,000 MW

The proven reserves correspond basically eo the three fields currently being developed: Cerro Prieto Los Azufres

Los Humeros The probable reserves correspond to new fields in which exploratory drilling is being done, such as La Primavera, Ceboruco, Araro, Ixtlan de 10s Hervores, Los Negritos, Tres Vergines, and enlargements of the fields currently under development The possible reserves correspond to an estimated 350 known thermal centers in the country.

(1) Proven

(2) Probable ( 3 ) Possible

( 4 ) Totals

Fig. 2 Mexico's Geothermal Reserves

INSTALLED POWER At present the use of geothermal energy in the country is principally concentrated in the Cerro Prieto field, which at the end of this year will have an installed power of 620,000 KW.

There are also 5 portable turbogenerators of 5 MW

each installed at Los Azufres.

With this there will be an installed power of

645 Wd, according to Table 1, which will make Mexico the third country in terms

of installed geothermoelectric power. TABLE 1 INSTALLED GEOTHERMOELECTRIC POWER IN MEXICO FWENCIA GDXE3M3ELFCIKCCA INSTAIADA EN

Mwm

Cerm Prieto I

Cerm Prieto 11 Cerro

Prieto I11

Los W r e s

'Unidad Unidad Unidad Unidad Unidad

1 2

3 4

5

37.5 Mw 37.5 M 37.5 rn 37.5 m 30.0 Mw

m

Unidad 1 Unidad 2

110.0

Unidad 1 Unidad 2

110.0 MN 110.0 Mw

110.0 KW

@plantas eiles 5 x 5 Mw

(1) Unit ( 2 ) Portable units

EXPANSION PXOGRAM Considering the reserve potential and the need to incorporate an increasing volume of geothermal power into the national network, the following installations have been planned:

1)

At Cerro Prieto, besides the nearly 6 2 0 MW installed, an addition of 220 Mw is being considered f o r 1992, to be s u p p l i e d b y 4 p l a n t s o f 55 FlIJ e a c h .

This

means a total of 840 MW for this field. Exploratory drilling recently done in the northeastern part of the field, beyond Ejido Nuevo Leon, has shown that the field extends much farther than originally estimated.

N o t to appear too optimistic, we do not want to give

figures on the possible additional potential.

We would hope that the tests

are concluded with mathematical models and that exploratory drilling be carried out to give reliable figures. 2)

Los Azufres currently has 5 turbogenerators in operation. 1982

Since November

construction of a 50 Wv' plant has been considered i n the sector called

Tejamaniles, which ought to go into operation by the end of 1986.

In 1987,.

7 portable units of

5

NTiJ each should g o into operation, as well as 2 plants

of 55 MW each, corresponding to Los Aziifres 1 and 11, planned for the end of 1988 and 1989, respectively. 'The construction o f Los Azufres 111, 55 Mid,

ought to be started by the middle of 1990, after 18 months of evolution based on the production history from the operation of Los Azufres I and 11. The expansion program for the fieldssof Cefro Rrieto and Los Azufres is illustrated in Fig. 3 .

3)

A s for L o s Humeros, in view of the results from the 4 drilled wells, it was

decided to install 3 units of 5 MJ each, back pressure type, about the middle of 1987. Two plants of 55 MW each are also planned for installation, in 1990 and 1991 respectively. According to the program and taking into consideration an annual sustained increase of 7 5 % , a potential of approximately 2 , 4 4 0 MW can be predicted for the end of the

century.

as shown in Fig. 4 .

Much of this power will be constituted by portable units, The above represents a saving of 35 million barrels of oil

each year, which is the equivalent o f the power supplied by thermoelectric plants.

n n

1992 1985 I984 1983

X

-

1982 1986 1987 I988 1989

Fig. 3 Expansion Program for Geothermal Energy

1111

2 m .

2000.

1500.

(1) 5 MW portable

IOOO.

units ( 2 ) Large plants ( 3 ) Year

i

85

90

95

Fig. 4 Installed Power as of the Year 2000

One of the important attainments established for the use of the geothermal resource is the use of 5 MW atmospheric discharge turbogenerators that are installed at the wellhead. These plants are considered to be a favorable solution especially if used as units for the evaluation of the reservoir and for permanent extraction of steam from strategic points in the field, to analyze its evolution, with the advantage that while the test is being carried out, the investment is being recovered. An important characteristic of these plants is their portability, so that if the well or reservoir fails prematurely, the equipment can be completely transferred to another well in-a few weeks. These portable plants can also be installed permanently as back pressure units when: a)

The noncondensable gas content of the well is very high.

b)

The reserve is too small to justify economically the design of a large plant This is the case at Tres Vurgines in Baja California Sur, where in a very

s h o r t time i t i s p o s s i b l e t o i n s t a l l p o r t a b l e u n i t s a t t h e w e l l h e a d t o r e p l a c e t h e g e n e r a t i o n t h a t i s c u r r e n t l y b e i n g performed by d i e s e l u n i t s . c)

T h e r e i s need f o r temporary g e n e r a t i o n w h i l e t h e f i e l d i s b e i n g e x p l o r e d and t h e l a r g e p l a n t i s b e i n g b u i l t . The t y p i c a l a r r a n g e m e n t of a p o r t a b l e un

t h i s type can be seen i n F i g . 5

I

SECADOR

I

/-,SILENCIADOR

Producing w e l l Silencer Separator Reinjection w e l l Globe v a l v e Steam Drier Surplus line Silencer Electrical generator Turbine

Fig. 5 T y p i c a l Arrangement of a P o r t a b l e Back P r e s s u r e Unit

T h e r e i s c u r r e n t l y g r e a t i n t e r e s t i n t h e u s e of p o r t a b l e u n i t s , n o t o n l y f o r t e c h n i c a l s o l u t i o n s t h a t t h e y r e p r e s e n t b u t a l s o b e c a u s e t h i s would b e a way of c o n t r i b u t i n g t o t h e development o f o u r own t e c h n o l o g i c a l c a p a c i t i e s . T h e r e was r e c e n t l y a d o m e s t i c c o m p e t i t i o n f o r t h e p u r c h a s e of 10 p o r t a b l e u n i t s of 5 MW e a c h , t h e m a n u f a c t u r e o f which f o r e s e e s a growing program o f d o m e s t i c p a r t s c i p a t i o n , t o t e r m i n a t e w i t h 80% m a n u f a c t u r e i n t h e c o u n t r y f o r t h e tenth unit.

STUDY PROGRAM

A s a r e s u l t of t h e growing a c t i v i t y i n t h e f i e l d of g e o t h e r m i c s , t h e s e a r c h

f o r more r a t i o n a l and e f f i c i e n t u s e of t h e r e s o u r c e h a s m o t i v a t e d v a r i o u s s t u d i e s . G r e a t e x p e r i e n c e h a s been g a i n e d i n t h e c o n d u c t i o n of g e o t h e r m a l f l u i d s w i t h t h e knowledge of t h e b e h a v i o r o f t h e two-phase f l u i d i n steam d u c t s .

I n w e l l s w i t h h i g h s a l t c o n t e n t , t h e p r e c i p i t a t i o n o f s i l i c a ' . i s i n t e n s e , as

a t Cerro P r i e t o ,

V a r i o u s e x p e r i m e n t s and t e s t s have been c a r r i e d o u t t o become

t h o r o u g h l y f a m i l i a r w i t h t h e mechanism t h a t c o n t r o l t h e p r e c i p i t a t i o n , and t h u s

be a b l e t o make s a f e r and more economic d e s i g n s .

A g r e a t Foncern h a s always been t h e u n d e r s t a n d i n g o f t h e phenomena o f c o r r o s i o n , whose d e t a i l s change from f i e l d t u f i e l d .

T h e r e f o r e e x t e n s i v e s t u d i e s have

been c a r r i e d o u t i n t h i s a r e a , a t C e r r o P r i e t o as w e l l a s a t L o s A z u f r e s .

A t p r e s e n t t h e r e i s g r e a t i n t e r e s t i n a p p l y i n g modern t e c h n i q u e s of making d e c i s i o n s on t h e i n c e r t i t u d e s i n t h e g e o t h e r m o e l e c t r i c p r o j e c t s i n o r d e r t o i n c o r p o r a t e them i n t h e e v a l u a t i o n of i n v e s t m e n t s t h a t a r e r o u t i n e l y made. Even though t h e a p p l i c a t i o n o f b i n a r y c y c l e p l a n t s a r e n o t comtemplated f o r t h e c o u n t r y , v a r i o u s e x p e r i m e n t s have been d i r e c t e d a t l e a r n i n g w i t h s u f f i c i e n t c e r t i t u d e t h e a p p l i c a b i l i t y of t h e s e systems.

I n this r e g a r d , i t i s i n t e r e s t i n g

t o n o t e t h e t e s t i n g of a b i n a r y c y c l e system w i t h demineralized water i n t h e s e c o n d a r y a p p l i c a b l e t o b r i n e s w i t h a h i g h c o n t e n t of noncondensable g a s s e s . With c o m p l e t i o n o f t h e c o n s t r u c t i o n of. t h e e v a p o r a t o r b a s i n f o r r e c o v e r y

o f p o t a s s i u m c h l o r i d e a t C e r r o P r i e t o , w i t h a p r o d u c t i o n e s t i m a t e o f a b o u t 100,000 t o n s p e r y e a r of t h i s s a l t , t h e commercial n o n - e l e c t r i c a l u s e of t h e g e o t h e r m a l r e s o u r c e s h a s been i n i t i a t e d i n t h e c o u n t r y .

F i g . 6 shows t h e a r r a n g e m e n t of a

p l a n t of t h i s t y p e . I

Fig. 6

Recovery of P o t a s s i u m C h l o r i d e from Geothermal B r i n e ( 1 ) Geothermal w e l l (2) Separator

( 3 ) Steam

( 4 ) Brine ( 5 ) C r y s t a l l i z a t i o n pond (6) Process (7) Brine

(8) 4 0 0 , 0 0 0 Ton/year (9) Others

CONCLUSIONS The r a t e of g e o t h e r m a l e x p l o r a t i o n a c h i e v e d i n t h e l a s t few y e a r s h a s a l l o w e d

u s t o i n c r e a s e t h e proven r e s e r v e s and t o p r e d i c t t h a t a n a n n u a l growth o f 15% per year i s a conservative estimate. The most r e l a v a n t a s p e c t s o f M e x i c o ' s g e o t h e r m a l f u t u r e c a n b e e x p r e s s e d by two f a c t s t h a t s t a n d o u t from t h e r e s t .

They a r e : t h e v e r i f i c a t i o n t h a t t h e

C e r r o P r i e t o r e s e r v o i r i s r a t h e r more e x t e n s i v e t h a n w a s t h o u g h t a c o u p l e o f y e a r s ago; and t h a t a t g e o t h e r m a l f i e l d s o f c o m p l i c a t e d v o l c a n i c s t r u c t u r e t h e i n s t a l l a t i o n o f back p r e s s u r e u n i t s l o c a t e d a t t h e w e l l h e a d i s a s a f e and economic s o l u t i o n , w i t h t h e a d d i t i o n a l a t t r a c t i o n t h a t t h e y c a n be m a n u f a c t u r e d i n g r e a t p a r t within the country. We have a l r e a d y p l a n n e d , a s i n d i c a t e d a t t h e b e g i n n i n g of t h i s a r t i c l e , 220 a d d i t i o n a l Mw's f o r C e r r o P r i e t o , 250 Eo? Los A z u f r e s , and 1 2 5 f o r Los Humeros. E x p l o r a t i o n i s b e i n g c o n t i n u e d a t L a P r i m a v e r a and o t h e r p r o m i s i n g l o c a t i o n s i n t h e s t a t e s of N a y a r i t and Michoacan. W e are p l a c i n g emphasis on r e d a c i n g t h e c o s t of g e o t h e r m a l g e n e r a t i o n of

e l e c t r i c power by improving t e c h n i q u e s f o r t h e placement of w e l l s and by t h e u s e

of g e o t h e r m a l w a s t e s f o r n o n - e l e c t r i c a l

purposes.

GEOTHERMAL PROGRAMS AT EPRI

Dwain Spencer

Paper Unavailable a t Time o f Publication

EL PROGRAMA DE GEOTERMIA DEL INSTITUTO DE INVESTIGACIONES ELECTRICAS P. Mulds, D. Nieva, J.L. Herndndez 'G. Instituto de Investigaciones El6ctricas

MEXICO

Resumen. Una breve descripci6n de las actividades de investigaci6n y desarrollo en el drea de la energla geotgrmica que se realizan en el Instituto de Investigaciones Elgctricas e s presentada. La gama de 10s estudios e investigaciones cu bre todas las dreas de actividad relacionadas con campos goet6rrnicos desde la exploraci6n, el desarrollo del campo

y la instalaci6n y operacidn de las centrales. Casi la totalidad de 10s trabajos se realizan para la Comisi6n Federal de Electricidad a traves de su Gerencia de Proye: tos GeotermoelGctricos.

EL PROGRAMA DE GEOTERMIA DEL I N S T I T U T O DE I N V E S T I G A C I O N E S ELECTRICAS

P . Mulds, D . Nieva, J . L .

Hgrnandez G .

I n s t i t u t o de I n v e s t i g a c i o n e s E l e c t r i c a s Apdo. P o s t a l 475 Cuernavaca, Morelos, 6 2 0 0 0 Mgxico, ( 7 3 ) 1 4 - 2 1 7 1

INTRMIUCCION.

Durante 10s tres A s que han transcuwido desde e l P r k r Seminario EPFU/IIE sobre Programas de Ceotennia, e l Instituto de Investigaciones El&ctricas ( I I E ) ha continuado sus labores de investigaci6n en esta &ea, de acuerdo a 10s li neamientos generales descritos en ese Seminario. E s t o s lineamientos fueron trazados con la intenci6n de m i m i z a r su -acto p r k t i c o en renglones tales corn e l a m t o de confiabilidad en l a evaluaci6n de recursos geot&micos, el abatimiento de costos en actividades de operacidn y desarrollo de estos rearms, y en l a minhizaci6n del impact0 de efectos negativos asociados con l a explotaci6n geot&mica, tales corn l a diseminaci6n de mntaminantes naturales en el mdio ambiente. La intensa actividad de desarrollo realizada en l a actualidad y planeada para e l futuro, p r parte de la Gerencia de proyedos Geotenrroel&ctricos, p r o w un amplio marco para l a utilizaci6n de 10s resultados de las actividades de investigacidn que se describ i r h en detalle a continuaci6n. EXPLDRACION.

Wcienterwnte se ha terminado un proyecto de evaluaci6n del &t& mgnetotelfkico en exploraci6n geot&vica, e l c u d fu6 financiado por e l Programa de las Naciones Unidas para e l Desa rrollo (m), administrado p r el I=, y lleva do a cabo por e l Centro de Investigacibn Cientz fica de Ensenada. Los resultados indican que e l r&todo tiene una utilidad mSs limitada en e l cas0 de exploraciSn geotennica, que en e l cam de exploraci6n petrolera, debido a agudos problems de ruido en las Irr?diciones efectuadas en yacimientos geot6rmims.

petroflsicas, con e l f i n de genera en la form d s rspida y eficiente p s i b l e un &lo concep tual del yacimiento. La generaci6n taprana de

dicho d e l 0 tiene una gran i n p r t a n c i a prSctica en dos aspectos. Por un lado permite r d u c i r e l k g e n de error en e l valor e s t k d o del recurso geot6.mico; p r otro lado permite UM mejor p~aneaci6ndel desarrollo subsecuente, puesto que provee bases para l a m j o r localizaci6n de nuevos pozos, la selecci6n de estratos apropiados para l a terminacidn de estos pzos,

etc. U n rrcdelo preliminar d e s c r i p t i v o de l a geom-

t r l a del yacimiento de U s Azufres, ha sido generado d i a n t e l a delineaci6n de zonas de ming rales de alteraci6n hidrotema1 (Cathelineau et a l , 1985). La geomtrla observada corresponde a un extenso yacimiento que , a profundidad, cubre l a totalidad del &ea del campo. E l fluldo del yacimiento ascierde a trav6s de dos sistemas columnares de descarga, dando lugar a las dos zonas principales de actividad superficial, Maritam5 en e l norte y Tejarraniles en e l sur. Mediate estudios qulrmco-isot6picos de 10s flufdos de porn de Los Azufres, se ha determig do una c i e r t a heteroqeneidad en l a constituci6n isot6pica de l a fase llquida del yacimiento. La ronstituci6n isot6pica de fluldos producidos p r pozos de vapor, indica que esta fase gaseosa se separa de una msa mcho mayor de fase 1L quida ( N i e v a et a l , 1983). Wiante l a rrodificaci6n de un procedimiento para e l cdlculo de exceso de v a p r en fluldos de p z o , se ha expli cad0 la extrema variabilidad en concentraci6n de gases no-condensables entre 10s distintos p zos de Los Azufres (Nieva e t a l , 1985).

En colaboraci6n con l a Universidad de Stanford, CARACTERIZACION Y EVALUACIGN DE RECURSOS GEO-

!rERMIcc)G. En esta secci6n se incluyen l a s actividades encaminadas a la integracidn y desarrollo de met2 dologla para la caracterizaci6n y evaluaci6n de yaciiientos, asl corn las aplicaciones a cams especlficos en e i c o . colaboraci6n con la mmisi6n Federal de Electricidad de M&co (CFE) , se ha trabajado en l a integraci6n de t6c nicas geol6gicas, mineral6gicas , geoqulmicas y-

se ha establecido un laboratorio para mdici6n de rad6n-222 en fluldos geot6rmicos, y se han analizado ya 10s fluldos de once pzos de Los Azufres. La variabilidad en l a concentraci6n de rad6n en e l flufdo de algunos p z o s de vapor, concuerda con una variabilidad observada en la constituci6n isot6pica de d i c b fluldo. Una PO_ sible explicaci6n que se ha ofrecido para este f e n 6 m o , es la posible existencia de mbs de una zona de aportaci6n para estos p z o s .

Se ha desarrollado una t6cnica para l a estimaci6n del volcnrW y caracterlsticas de l a fuente La t6cde calor de yn yacimiento geot&mico. nica se basa en l a cuantificaci6n de 10s procesos de cristalizaci6n fraccionada y de 10s Ml h e s de l a s fomciones igneas en l a zona ba jo estudio. Un d t o d o original ha sido desarrollado para l a determinaci6n de presi6n de yacimiento, y de l z dices de productividad mdsica y t6rmica, a partir de curvas de producci6n de pozos. La principal ventaja de este m5todo es e l hecho de que requiere s610 de M c i o n e s realizables en l a superficie, l a s males mrmhwnte se llevan a c a b en forma rutinaria (Iglesias e t a l , 1985a). Mdiante l a aplicaci6n de este d t o d o a un nGme^) de pozos de Los Azufres ha sido posible gg nerar un nodelo unidimensional del yaciiento, e l cual describe la variaci6n de condiciones termdin&nicas del fluldo con l a profundidad. E l -10 muestra l a existencia de t r e s zonas: una a profundidad, de fase llquida; una intermdia, de dos fases con llquido dcaninante; y una de m o r profundidad, de dos fases con vapor dominante (Iglesias et a l , 198533; Iglesias e t al, 1985~). Se nu3dific6 un d t o d o para est* permabilida_ des relativas agua/vapr e n yacimiento. E l m5todo se aplic6 a datos de err0 Prieto, obteni6ndose l a s primeras estimaciones publicadas para 10s par5mtros mcionados (Iglesias e t al, 1985d).

Se valid6 una metodologla para analizar results dos de pruebas de pozo, restando e l efecto de almacenaniento, empleancb datos del c a n p geot6rmiw de Cerro Prieto. Esta tecnica permite obtener infomci6n, de otra form irrecuperable, de pruebas de presi6n que resulten denas+ do cortas para un d l i s i s semilogarftmico; p r l o tanto pernite e l diseiio de pruebas nbs cortas, m s costosas y con m o r riesgo para e l equip de mdici6n a fond0 de p z o (Ju6rez B a g 110, 1982). U n a metdolog€a para l a determinaci6n de circu-

laci6n interna dentm del p z o , entre zonas de alimentaci6n a distintas profundidades, ha sido desarrollada y aplicada a pozos de Cerro Prieto. E s t a mtodologfa constituye una alternativa prsctica y de m o r costo, al uso de instrumental especializado ("spinners") (Cast&& y Exne, 1981). h colabraci6n con e l Departamento de Ingenier l a Petrolera de l a Universidad de Stanford, se llev6 a c&u una prueba de conectividad entre dos p z o s productores y dos p z o s seleccionados para reinyecci6n en Los k u f r e s , emplehdose ion ycduro COIID trazador. U s resultados no

muestran conectividad entre 10s pozos observados. En l a misma prueba se investig6 l a p s i b i lidad de u t i l i z a r e l ion cloruro, presente en forma mncentrada en l a salmuera separada, corn3 un trazador conservativo. se encontr6 que l a

precisi6n de anslisis qu5jnim del ion cloruro es suficiente para su uso en l a forma descrita, y w n esto se abri6 l a posibilidad de reducir d r 6 s t i c m n t e 10s costos de pruebas futuras (Iglesias e t a l , 1985e). En e l Laboratorio de Simulaci6n de Yacimientos

se han continuado 10s estudios de propiedades petroflsicas de nGcleos de zonas productoras de Cerro Prieto y LCJS Azufres. Para e l cas0 de Ce_ rro mieto, se ha encontrado una correlaci6n plrica entre pern-eabilidad y temperatura, l a cual juega un papel importante en l a interpretg ci6n del historial de producci6n del yacimienta, y en l a planeaci6n de pollticas de reinyecci6n Por otro lado, (Contreras et a l l 1982a). se ha llevado a cabo un estudio para evaluar e l 60 a l a f o m c i 6 n ocasionado p r l a utilizaci6n de lodos de perforaci6n; se ha encontrado que se puede ocasionar una reducci6n de hasta 30% en pern-eabilidad, F r o esto e s reversible d a n t e d t o d o s mcEinicos (Arenas et a l , 1982). A s l mism, un estudio de ccollpresibilidad y a x ficiente de expansi6n t6rmica de areniscas ha permitido e l desarrollo de una t W c a para l a estimacidn de prosidad a una determinada cornpresi6n o temperatura (Contreras e t a l , 1982b). Otra contribuci6n ha sido l a recopilaci6n de rg sultados de mediciones en laboratorio de propig dades petroflsicas de nGcleos de Cerro Prieto, l a m a l incluye cam una fracci6n importante nuestros propios resultados. U s mediciones i; cluldas son densidad, prosidad, permabilidad, mnpresibilidad, expansividad t-ca, conductividad t&mica, velocidad de o n h s S6nica.s y resistividad e l k t r i c a , a s l c m 10s efectos de temperatura y presi6n sobre estas propiedades (Contreras e t a l , 1984). Ftecientemnte se han mdido tambih propiedades a d s t i c a s y electricas de nGcleos de Cerm Prieto (Contreras y King, 1985). Se han llevado a cabo mediciones de propiedades petroflsicas de varios nGcleos de zonas productoras de Los Azufres. IDS p a r h t r o s mdidos han sido prosidad, perrneabilidad, conductivi-

y ccanpresibili dad Grmica, difusividad t&mica dad, siendo estas mediciones l a s Gnicas existent e s sobre materiales de Los Azufres. CONSIWCCION DE FQZOS.

En esta &ea l a s actividades de investigaci6n est& dirigidas a1 mjoramiento de flufdos de perforaci6n y de cemntos para l a construcci6n de p z o s geot&micos, a s l corn a l a evaluaci6n y soluci6n de problemas que afecten l a vida G t i l de 10s pozos. Mediante e l estudio de una variedad de formulaciones de lodos de perforaci6n, somtidas a cop diciones de campo s h l a d a s en e l laboratorio, se ha avanzado considerablerrente en l a tarea de definir l a f o d a c i 6 n 6ptima para diferentes estratos geol6gicos y condiciones tennodin5micas. Debido a l a d i f i c i l situaci6n econ6mica

del pals, se ha hecho un esfuerzo p r localizar productos nacionales apropiados para l a substituci6n de 10s h p r t a d o s . CBm e j q l o de un logro en este rengl6n, se puede citar e l cas0 de una bentonita de fabricaci6n nacional, l a cual fu6 estudiada y reconwdada para su us0 en lodos de perforaci6n. Otro ejemplo es e l de un obturante para utilizarse en e l tapnamiento de zonas de g r d i d a de c i r c u l a c i h del fluldo de perforacibn. Ambos materiales han sido ya utilizados e x i t o s m t e en e l campo. En esta misrn lfnea de actividad, se han estudiado tres dispersantes, 10s males han mstrado ser apropiados para su us0 a temperatuxas hasta de 250'C.

E h l o que respecta a cmentos, se complet6 e l p r o g r m de pmebas a fond0 de pozo de diversas lechadas de cemnto, para la elabraci6n de recomendaciones de =I. En este prograrna particL del I I E , l a Comisi6n Federal de paron, a&s Electricidad, l a Oficina Nacional de Esthdares (National Bureau of Standan.: NES) , e l Laborab r i o Naciond de Brookhaven (F3mokhaven National Laboratory: m),e l Instituto Sudoccident a l de Investigaci6n (Sout!!st Research Labratory:S&) , asl corm m q x S a s privadas e*cializadas en perforaci6n y construcci6n de po20s.

La muestra de m n t o preparada en e l I I E

fu6 inclulda en e l grupo que present6 e l m j o r catportmiento bajo condiciones de fondo de po20.

Al igual que en e l cam de lodos de perforaci6n, se ha hecho un esfuerzo considerable para ident i f i c a r materiales nacionales apropiados para l a preparaci6n de m n t o s geot6rmicos. E l esfuerzo ha resultado exitoso, y CFE ha completado ya varios pozos utilizando exclusivawnte m a teriales nacionales. Se llev6 a cab0 un estudio de 10s procesos de corrosi6n que limitan l a vida G t i l de 10s p z o s . m s resultados indican que la corrosi6n por piy que la corrg cadura es e l proceso d s -no, si6n OcUzTe en la parte externa de l a tuberla, probablemente en zonas con c m n t a c i 6 n defectug sa donde l a tuberla entra en contact0 con l a salmuera

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Se llev6 a cab0 un breve estudio de muestras de incrustaci6n en tuberla de p z o s de a l t a entalpla de Cerro Prieto, identifi&dose 10s componentes principales (silicatos m r f o s y cristalinos, s u l f u r o s de p l m , cinc, cobre y armcor carbonato de calcio, etc.) Se llev6 a cabo tambi6n un estudio te&ico, consistente en e l cdlculo de mndiciones teficodin&nicas del fluldo a fond0 de p z o , as€ rn e l ctilculo de las constantes de solubilidad de 10s posibles incrustantes bajo esas condiciones, encontrh+ 5e que l a presencia de la mayorla de 10s materiales encontrados podr€a haberse predicho.

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EXPLQ'IACION

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En esta secci6n se incluyen actividades de investigaci6n relacionadas con e l diseiio de @po para e l manejo de fluldos en superficie y pa_ r a generacidn elgctrica, soluci6n de problemas de contaminaci6n, recuperaci6n de materiales va liosos disueltos en fluldos de desecho, y aprovechamiento de energla de desecho, tanto para gmeraci6n e l k t r i c a c a w para su posible us0 direct0 en procesos industriales. Una de l a s principales llneas de investigaci6n que se han seguido durante 10s G l t h s aiios, ha sido la optimizaci6n del d i s e k de equip SUFf i c i a l para uso geot6rmico. Dvltro de este r E g16n de actividades se puede inclufr e l diseiio del arreglo en dos niveles de 10s separadores de vapor de l a s plantas de Cerro Frieto 11 y 111, e l cual fu6 inplementado para evitar 10s problems de vibraci6n asociados con flujos bifdsicos. La prueba realizada en e l pozo T-388, as€ c a m e l ccknportamiento del equip0 durante e l tienip que l a planta lleva en operaci6n, c o ~ firman e l hecho de que e l problena ha sido resuelto s a t i s f a c t o r i m t e . s i n embarqo, quedan ciertas dudas sobre e l correct0 funcionamiento del muestreador de vapor de la ASME, p r l o mal se ha integra& un g r u p , con personal m t o de CFE c m del IIE, para l a realizaci6n de pruebas con e l objeto de determinar l a repre=tatividad del muestreo. En lo que respecta a otros equips para m j o de fluldos, se ha &s&do un modelo matendtic0 Asf para separadores de vapor del tip "U". misno, se est5 trabajando en colab0raci6n con CFE en l a prueba de un n k o de 17Slvulas de ferentes t i p s , m t i d a s a condiciones de campo geot6.rmicor con e l objeto de determinar su aplicabilidad. Por otro lado, se ha llevado a cab0 una revisidn de las condiciones de operaci6n de silenciadores en IDS Azufres, y se ha cambiado e l diseiio de aquellos que se encontraron operando con un nivel de ruido inaceptable. Se ha emprendido un estudio a fondo del d i d o mecfmico de estas unidades, con e l f i n de optim i z a r su eficiencia para la reducci6n del nivel de ruido, para reducir su cost0 de construcci€h, y para minimizar problernas de incrustaci6n y de tensi6n Irecb-Lica.

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Nuestro paquete de a u t o FLUDOF, para diseiio de llneas para flujo bifdsico, se encuentra en proceso de d f i c a c i 6 n para inclufr la capacidad de tratamiento de problems de confluencia de un n6ner-o de lheas. E l trabajo se enment r a en l a s etapas iniciales, y se requiere a h l a validaci6n con observaciones de lakoratorio y de campo. En relaci6n con este t a m , se ha avanzado en l a organizaci6n del Segundo Smhar i o Internacional sobre Flujo Bifdsico, e l cual tendrd lugar en Cuernavaca, en e l mes de Agost0 de 1986.

En relaci6n con problems de incrustaci6n ED equip de superficie, se han Ilevado a C&I estudios para determinar 10s problemas que pdrlan presentarse en tuberlas para s a h e r a dE: desecho de 10s p z o s de a l t a entalpla de m o Prieto 11 y 111. La presi6n de separaci6n en 10s separadores de estas plantas se f i j 6 t c m do en consideraci6n l a p s i b l e o m e n c i a de i G crustaci6n. Por otro lado, se encuentra er prg ceso un estudio para l a determinaci6n del I&tcdo r&s eficiente para l a l i q k e z a de silencig dores y tuberlas. En l o que respecta a problemas de contaminaci6n por desechos geot6rmicos, se han llevado a cab0 una serie de estudios de sistemas para l a elk: nacibn, y en algunos casos l a remperaci6n, de substancias contaminantes. colabraci6n con EPRI, se ha llevado a cab0 un program de pruebas del Sistema Condensador-Evaprador para l a eliminaci6n de H2S, CO2 y otros gases m-mnhsables en e l vapor, antes de su entrada a l a turbina. Por otro lado, se han continuado 10s estudios relacionados con l a eliminaci6n de H2S mdiante e l &todo de canbusti6n; en l a actuali dad se est5 terminando un program de pruebas, y se est5 llevando a cab0 e l di&o de una plan t a para l a incineraci6n de 10s gases desechados de l a plantii de Cerro Prieto I. Se estd llevando a cab0 l a segunda fase de un estudio sobre recuperaci6n de b r o de l a sar a geothnica d i a n t e e l empleo de resinas intercambiadoras de iones; en l a p r b r a fase se estableci6 l a factibilidad t6cnica, y se inici6 e l estudio de 10s aspectos econ6micos. Hastael -to l a evidencia indica que, bajo l a s condiciones ecOnOmicas actuales, e l proceso de remperaci6n de boro resultarla ecodmico, siempre y mando no hubiera efectos de degradaci6n en l a resina, a corto plazo.

En l o referente a l a utilizaci6n de fluldos gee_ t6rmicos de baja entalpfa, se han continuado 10s estudios sobre generaci6n con sistemas de ciclo orgdnico Rankine, para lo cual se cuenta con dos plantas piloto (una de 50 KW y o t r a de 1 0 Gv)instaladas en LCIS Azufres. Por otro lado, se ha construfdo ma banba de calor de 30 KWt, y se ha evaluado su f u n c i o d e n t o con aqua a 8OOC. As€ m i m , se ha constrUld.0 un frigerador con una capacidad de 3 toneladas, e l cual enpleard salmuera de desecb.ccarrs fuente de energla; este equip se encuentra en l a actualidad en etapa de manque y pruebas iniciales.

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Se est5 haciendo h f a s i s en e l estudio de distintos tipos de cambiadores de calor, con e l ob jet0 de m i n i m i z a r 10s problemas de incrustaci6n y corrosi6n asociados con l a utilizaci6n de fluldos geothnicos. Se estd llevando a cab0 un estudio en e l campo geot6rmico de Los Azufres, con e l objeto de evaluar e l efecto de esos procesos sobre l a eficiencia de cambiadores de tip de tuberla y coraza. A escala de

laboratorio, se han continuado 10s estudios con un sistema piloto de cambiador de lecho fluidizado, con e l objeto de definir 10s parbTletros de diseiio para un cambiador de 200 Kwt, e l cual serd probado en e l campo, en conjunci6n con l a s plantas de ciclo org&lico Rankine. Por otro 15 do, se estA trabajando en e l diseiio de un cambiador de calor capaz de u t i l i z a r e l flujo tot a l de un pozo geotSrmico, incluyendo lfcpido, vapor y gases no-condensables. U n a vez constru_ fdo, este cambiador se probard en e l campo.

Se ha desarrollado e inplerrentado un sistema ccanputarizado denaninado SIGEO, e l cual permite l a colecci6nr almacenamiento y reproducci6n de infomci6n t6cnica generada durante e l de110 de c m p s geot&mi.cos. Hasta l a fecha, 10s casos a 10s cuales se ha aplicado son 10s campos de Los Azufres, La Primvera y Los H m ~ r o s . E l SIGEO es aplicable a infonnaci6n generada desde la etapa de exploraci6n hasta l a etapa de explotaci6n continua. C a m ejemplo del tip de infomci6n que se puede colectar y almacenx, se puede c i t a r l a i n f o m c i b n geol6gica, g m mica, geoffsica y termodin5mica obtenida durant e l a perforaci611, inducci6n, prueba y utilizaci6n de un p z o geot6rmico. E l SIGEO tiene una estructura mdular, la cual permite i n t e g r a nuevos nfdulos de datos para e l procesamiento, p r ejgnplo, de infomci6n relacionada con materiales, refacciones, equip y aspectos econ6micos. Actualmente se est& desarrollando herramientas de 06anputo para l a explotaci6n del banco de datos. Dichas herramientas proveen fa cilidades de graficaci6n en 2 y 3 dimensiones, as€ a m herramientas anallticas a manera de apyo para l a evaluaci6n de yacimientos geot6rmicos. Ccmo ejemplo de estas Gltims pdems m c i o n a r : herramientas para l a interpretacibn de pruebas de inyectividad, y de pruebas de gas t o variable; para l a obtenci6n de curvas caracterfsticas de producci6n; para e l seguimiento de l a evoluci6n de l a presi6n de cabezal, Fresi6n de fondo, temperatura de fondo, producci6n de lfquido, vapor y mezcla, etc. Se ha iniciado una llnea de investigaci6nr nueva e importante, relacionada con e l desarrollo de capacidad tecml6gica en IGxico para e l dise fio y fahricaci6n de turbgeneradores geot&mi-cos. Para este profisit0 se ha inplemnta6o un esquema de transferencia de teamlogla, d i s t i n to a1 tradicional, en e l cual l a parte receptor a e s t 5 integrada p r tres entidades. h a de &stas es l a 1nstituci6n Tecm16gicar en este E so e l IIE, la cual t e e 5 h funci6n de garanti z a r l a asj.dlaci6n canpleta de l a tecnologfa. m a entidad l a constituye e l principal U s u a r i O de 10s productos de esta tecnologfa, en este SO l a Federal de Electricidad. tc cer entidad es una coqyifa naciond, l a C u a l es l a receptors f i n a l de l a tecrdogfa, Y es se encargars de l a fabricaci6n Y -cig lizaci6n de 10s turgogeneraibres. Se ha Ya tratiido l a transferencia de tecnologfa para e l fiseh, fabricaci6n e instalaci6n de turbgeneradores de 3 , 5 y 7 MW,con l a campaii€a mshiba.

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L a m y o r f a de las actividades arriba sekladas han sido financiadas p r la Gerencia de proyect o s Geotermel&tricos, de l a Ccanisi6n Federal de Electricidad, y l a participacitjn de s u perso_ n a l tRcniCx, h a sido de v i t a l importancia para e l h e n desarrollo de ems estudios. IDS autores desean expresar su a g r a d e c f i e n t o a

10s jefes de 10s distintos proyectos del P r o q G ma de Geotermia del IIE, por la i n f o m c i 6 n pro_ porcionada

.

REFERENCIAS. Arenas A., I g l e s i a s E., Izquierdo G., Guevara M. Oliver R. y Santoyo S. (1982) "Effects of Contamination by G e o t h e n ~ lD r i l l i n g Mud on Labor a t o r y Dzterminations of Sandstone pore P r o p ties". Proc. Eight Workshop on Geothermal Reser v o i r Engineering, Stanford University, pp 205-210. C a s t a i e d a M. y Horne R.N. (1981) "Location of Production !?,ones w i t h Pressure Gradient Logging". GRC Trans. 5, 275-278.

, O l i v e r R. , N i e v a D. y Garfias A. (1985) "Mineralogy and d i s t r i b u t i o n of hydrothermal mineral zones in L3s Azufres (M5xico) Cathelineau M.

geothermdl field". Geothennics 14, 49-57. Contreras E. y King M.S. (1985) "Acustic and E l e c t r i c a l Properties of Cerro P r i e t o Core Samples". Proc. Tenth workshop on Geothermal Reservoir Engineering, Stanford university, pp 307-310. Contreras E., I g l e s i a s E. y F%rmjo F. (1984) " L a b o r a t o r y - m a s d Physical Properties of Cerro Prieto RDcks. A Review of Early Work and Presentation of New Data". GRC Wans. 8, 193-202.

I g l e s i a s E., Arellano V., Garfias A., W l i n a r R. y Miranda C. (1985a) "Estimates of t h e Reservoir Pressure, the proauctivity Index, and a T h e m 1 Power Productivity Index from Product i o n output curves of ~eothemiwlls", mti da a r e v i s i 6 n a la Sociedad de Ingenieros P e t r g leros de AIME (SPE-AIME) , m u s c r i t o SPE-13755. I g l e s i a s R. , Arellano V., Garfias A. y Miranda C. (1985b). "!lhNatural Thern~d*c S t a t e of the Fluid o f Los Azufres Geothermdl Reservoir". Proc. Tenth Workshop on Gezkhermal Reservoir Engineering, Stanford University, pp 241-246. I g l e s i a s E., Arellam V., Garfias A., MirandaC. y Arag6n A. ( 1 9 8 5 ~ )"A One-Dhensional V e r t i c a l mdel of t h e IDS Azufres, e i c o , Geothermal W s e r v o i r in i t s N a t u r a l State". A presentarse Anual de 1985 d e l Consejo de Ree n la Re&& CUTSOS Geo~rmicos. I g l e s i a s E., Arellano V. y Wlinar R. (1985d) "steam and W a t e r Relative Penneabilities for the C e r r o P r i e t o Geothermal Reservoir". Proc. Tenth workshop on Geotherml Reservoir Enginee r i n g , Stanford University, pp 301-306. I g l e s i a s E., Garfias A., Nieva D., Miranda c., M a r t h e z A., Cabrera J. and Barrag& R.M. (198%) "The F i r s t multi-well mlti-tracer test i n the LOS Azufres Geothermal F i e l d ; Progress Report". Proc. Tenth Wrkshop on -them1 Reservoir Engineering, stanford University, pp 265-272. V e m S . , Corona A.,

Ju&ez Badillo C.E. (1982) "Efectos Kidrodi&micos de A l m c e n d e n t o en Pozos Geot6miCos: Pplicaci6n a1 Anglisis de Pruebas de Presi6n para Evaluar Propiedades de Yacimientos ckot&micos". Tesis de Licenciatura, Facultad de C i p cias, Universidad N a C i O M l A u t b m de &iw.

Contreras E., I g l e s i a s E. y S n c h e z J. (1982a) "Estudios de =abilidad a A l t a Temperatma de N G c l e o s de Cerro Prieto". m r i a s , Cuarto Simposio Internacional sobre e l Campo G e o t 6 d a de Cerro Prieto, Guadalajara, Agosto de 1982.

Nieva D., Gonz%lez J. y Garfias A. (1985) "Evidence of Tvm E x t r a F l m R e g h s -rating Zones of Different Wells f r o m i n the Produ&ion Los Azufres". Proc. Tenth Workshop on Geothermdl Reservoir Engineering, Stanford University, pp 233-240.

Contreras E., I g l e s i a s E. y Bermejo F. (1982b) "Effects of Temperature and S t r e s s on the Compressibilities, Thermal Expansivities and Porosities of Cerro P r i e t o and m e a Sandstones t o 9000 p s i and 28OOC". proc. Eight Workshop on Geothermal Reservoir Engineering, Stanford Univ e r s i t y , pp 197-203.

Nieva D., Quijano L., Garfias A . , Barrag& R.M. Y m e d o F. (1983) "Heterogeneity of t h e Liquid Phase, and Vapor Separation i n IDS Azufres ( e i c o ) Geothenral Reservoir". m c . Ninth Workshop on Geothermal Reservoir Enginee r i n g , Stanford University, pp 253-260.

THE GEOTHERMAL PROGRAM of the INSTITUTO DE INVESTIGACIONES ELECTRICAS

P. Mulas, D. Nieva, J . L . Hernandez G . Instituto de Invrstigaciones Electricas Apdo. Postal 475 Cuernavaca, Morelos, 62000 Mexico, (73) 14-2171

SUMMARY We offer a brief description of -.the research

and

devehpment

activities

in the area of geothermal energy being performed by the Instituto de Investigaciones Electricas [Electrical Research Institute].

The range of study and research

covers all areas of activity related to geothermal fields, from exploration and deveopment of the field to installation and operation of the power-plants. Almost all the work is done for the Comision Federal de Electricidad [Federal Electricity Commission] through its Gerencia de Proyectos Geotermicos [Geothermal Project Administration].

INTRODUCTION During the three years that have passed since the First EPRI/IIE Seminar on Geothermal Programs, the Instituto de Investigaciones Electricas (IIE) has continued its research in this area along the general lines described in the Seminar. These guidelines were drawn with the intention of maximizing its practical impact in areas such as increasing the reliability o f the evaluation of geothermal resources, lowering the cost of operating and developing these resources, and minimizing the negative affects associated with geothermal use, such as the dispersal of natural pollutants in the environment.

The intense development activity

being realized at present and planned for the future by the Gerencia de Proyectos Geotermoelectricos provides a large framework for the use of the results of the research activities described here in detail.

EXPLORATION Recently a project was completed that evaluated the magnetotelluric method of geothermal exploration.

It was financed by the United Nations Development

Program (UNDP), administered by IIE, and carried out by the Centro de Investigacion Cientifica de Fnsenada [Scientific Research Center of Ensenada].

The results

indicate that the method is of more limited use in geothermal exploration than in petroleum exploration, due to acute problems of noise when measuring in geothermal reservoirs.

CHARACTERIZATION AND EVALUATION OF GEOTHERMAL RESOURCES This section-covers the activities directed at integrating and developing-a methodology for characterizing and evaluating reservoirs, as well as application of

if: in

specific cases in Mexico.

In collaboration with the Comision Federal de

Electricidad (CFE) of Mexico, work was done to integrate geological, mineralogical, geochemical, and petrophysical techniques, in order to generate a conceptual model of a reservoir as quickly and efficiently as possible.

Early generation of the

model has great practical importance for two reasons. On the one hand it allows us to reduce the margin of error in the estimated value of the geothermal resource; and on the other hand it permits better planning oft-subsequent development, since it provides a basis for the better positioning of new wells, the selection of the

right strata for terminating them, and so forth.

A preliminary descriptive model of the geometery of the Los Azufres reservoir was generated by delineating zones of hydrthermally altered minerals (Cathelineau et al., 1985).

Its geometery corresponds to an extensive reservoir which, deep

down, covers the entire area of the field.

The fluid from the reservoir ascends

through 2 columnar discharge systems, resulting the 2 principal zones of superficial activity, Maitaro in the north and Tejamaniles in the south. Chemical-isotopic studies of the well fluids from Los Azufres have revealed a certain heterogeneity in the isotopic constitution of the liquid phase of the reservoir.

The isotopic constitution of fluids produced by steam wells indicates

that this gaseous phase is-sepaeate -from a liquid phase of much greater mass (Nieva et al., 1983).

Modification of a procedure for calculating excess steam

in well fluids has been used to explain the extreme

variability in concentration

of noncondensable gasses among the various wells of Los Azufres (Nieva et al., 1985). In collaboration with Scanford University, a laboratory was set up to measure radon-222 in geothermal fluids; and the fluids f r o m 11 Los Azufres wells have already been analyzed.

The variability in radon concentration in the fluid from

some steam wells accords with a variability observed in the isotopic constitution of the fluid. A possible explanation of thisphenomenon is the possible existence

o f more t h a n one i n f l o w zone f o r t h e s e w e l l s .

A t e c h n i q u e h a s been developed f o r e s t i m a t i n g t h e volume and c h a r a c t e r i s t i c s of t h e h e a t s o u r c e of a geothermal r e s e r v o i r .

The t e c h n i q u e i s b a s e d o n t h e

q u a n t i f i c a t i o n o f p r o c e s s e s of f r a c t i o n a t e d c r y s t a l l i z a t i o n and i g n e o u s f o r m a t i o n s i n t h e zone b e i n g s t u d i e d . An o r i g i n a l method h a s been d e v e l o p e d f o r d e t e r m i n i n g r e s e r v o i r p r e s s u r e , and

m a s s and h e a t p r o d u c t i v i t y i n d i c e s , from w e l l p r o d u c t i o n c u r v e s .

The c h i e f advan-

t a g e of t h i s method i s t h a t i t r e q u i r e s o n l y measurements t h a t can b e made on t h e s u r f a c e , which n o r m a l l y a r e made r o u t i n e l y ( I g l e s i a s e t a l . , 1 9 8 5 a ) .

By a p p l y i n g

t h i s method t o a number o f w e l l s a t Los A z u f r e s i t h a s been p o s s i b l e t o g e n e r a t e

a one-dimensional model of t h e r e s e r o i r , which d e s c r i b e s t h e v a r i a t i o n i n thermodynamic c o n d i t i o n s o f t h e f l u i d w i t h t h e d e p t h .

The model shows t h e e x i s t e n c e

o f t h r e e z o n e s : o n e , which i s deep and i n l i q u i d p h a s e ; one i n t e r m e d i a t e . a n d twop h a s e w i t h l i q u i d dominant; and one n o t s o d e e p , w i t h two p h a s e s w i t h steam dominant ( I g l e s i a s e t a l , , 198513; I g l e s i a s e t a l . , 1 9 8 5 ~ ) . There w a s m o d i f i c a t i o n o f a method f o r e s t i m a t i n g r e l a t i v e w a t e r l s t e a m permeab i l i t i e s in reservoirs.

The method w a s a p p l i e d t o d a t a from C e r r o P r i e t o t o o b t a i n

t h e f i r s t p u b l i s h e d e s t i m a t e s f o r t h e s t a t e d parameters ( I g l e s i a s e t a l . , 1985d).

A methodology was v a l i d a t e d f o r a n a l y z i n g r e s u l t s o f w e l l t e s t s , s u b t r a c t i n g t h e s t o r a g e e f f e c t , u s i n g d a t a from t h e C e r r o P r i e t o g e o t h e r m a l f i e l d .

This

t e c h n i q u e p r o v i d e s o t h e r w i s e u n o b t a i n a b l e i n f o r m a t i o n from p r e s s u r e t e s t s t h a t are too s h o r t f o r a semilogarithmic a n a l y s i s .

I t t h e r e f o r e p e r m i t s t h e d e s i g n of

t e s t s t h a t a r e s h o r t e r , l e s s c o s t l y , and l e s s r i s k y f o r t h e w e l l - b o t t o m measurement equipment ( J u a r e z B a d i l l o , 1 9 8 2 ) .

A methodology f o r d e t e r m i n i n g i n t e r n a l c i r c u l a t i o n w i t h i n a w e l l , between f e e d zones of d i f f e r e n t d e p t h s , was d e v e l o p e d and a p p l i e d t o w e l l s of C e r r o P r i e t o . T h i s methodology c o n s t i t u t e s a p r a c t i c a l and l e s s c o s t l y a l t e r n a t i v e t o t h e u s e of s p e c i a l i z e d i n s t r u m e n t s ("spinners")

( C a s t a n e d a and Horne, 1 9 8 1 ) .

I n c o l l a b o r a t i o n w i t h t h e P e t r o l e u m E n g i n e e r i n g Department of S t a n f o r d U n i v e r s i t y , a t e s t was done on c o n n e c t i v i t y between two p r o d u c i n g w e l l s and two w e l l s s e l e c t e d f o r r e i n j e c t i o n a t Los A z u r e s , u s i n g i o d i d e as a t r a c e r . r e s u l t s do n o t show any c o n n e c t i v i t y between t h e w e l l s .

The

The same t e s t i n v e s t i g a t e d

t h e p o s s i b i l i t y o f u s i n g t h e c h l o r i d e i o n , p r e s e n t i n c o n c e n t r a t e d form i n t h e separated b r i n e , as an observable t r a c e r .

I t was found t h a t t h e p r e c i s i o n o f

c h e m i c a l a n a l y s i s of t h e c h l o r i d e i o n i s s u f f i c i e n t f o r i t s u s e i n t h e way d e s c r i b e d ,

and this uncovered the possibility of greatly reducing the costs of future tests (Iglesias et al,, 1985e). - ,

The studies of petrophysical properties of cores from Cerro Prieto and Los

Azufres production aones continued to be studied, at the Reservoir Simulation Laboratory.

In the case of Cerro Prieto, they found an empirical correlation

between permeability and temperature, which plays an important role in the 'nterpretation of the production history of the reservoir and in the planning of reinjection policies (Contreras et a l . , 1982a).

O n the other hand, a study was

made to evaluate the damage to the formation caused by use of drilling mud.

It

was found that there could be a 30% reduction in permeability, but this is reversable by mechanical means (Arenas et al., 1982).

Likewise, a study of compressi-

bility and thermal expansion coefficients of sands permitted the development of a technique for estimating the porosity at a particul.ar compression or temperature (Contreras et al., 1982b). Another contribution was the :compilation of results of laboratory measurements of the petrophysical properties of cores from Cerro Prieto, our,own results being a large fraction of it.

The measurements included are density, porosity,

permeability, compressibility, thermal expansivity, thermal conductivity, velocity of sonic waves, and electrical resistivity, as well as the effects of temperature and pressure on these properties (Contreras et al., 1984).

Acoustic and electrical

properties of cores from Cerro Prieto have also been measured recently (Contreras and King, 19851, There have been measurements of petrophysical properties of various cores from production zones of Los Azufres.

The parameters measured have been porosity,

permeability, thermal conductivity, thermal diffusivity, and compressikility, these measurements being the only existing ones on materials from Los Azufres.

WELL CONSTRUCTION

In this area the research activities are directed at the improvement of perforaeion fluids and cements for the construction of geothermal wells, as well as at the evaluation and solution of problems that affect the service life of the wells. Study of a variety of drilling mud formulations, subjected to simulated field conditions in the laboratory, has considerably advanced the t a s k of defining the optimal formulation for different geological strata and thermodynamic conditions.

Due to the country's difficult economic situation, an &Tarthas

been made

. .. . . . .. . .

this is a domestically manufactured bentonite, which was studied and recom for use in drilling muds.

Another example is an obturant for use in pluggLll&

areas of drilling fluid circulation loss. successfully in the field.

Both materials have already been used

In this same line of activity, three dispersants

have been studied, which have been shown to be suitable for use at temperatures up to 250°C. In regard to cements, the well-bottom testing program for various slurries was completed, to apply API recommendations. Besides IIE, this program was participated in by the Comision Federal de Electricidad, the National Bureau of Standards, the Brrokhaven National Laboratory, the Southwest Research Laboratory, and private firms specializing in the drilling and construction of wells.

The

cement sample prepared by IIE was included in the group that showed the best performance under well-bottom conditions. A s in the case of the drilling muds, considerable effort was made to identify

domestic materials suitable for the preparation of geothermal cements.

The effort

was successful, and CFE has already completed several wells using domestic materials exclusively. A study was made of the processes of corrosion that limit the service life

of the wells.

The results indicate that pitting is the most damaging corrosive

process, and that the corrosion occurs on the outside of the pipe, probably in areas with defective cementation where the pipe is in contact with brine. A short study was done on samples of incrustation in pipes of high enthalpy

wells of Cerro Prieto, identifying the principal components (amorphous and.crystalline silicates, sulfides of lead, zinc, copper, and arsenic, calcium carbonate, etc.). A theoretical study was also done, consisting of calculating thermodynamic condi-

tions of the well-bottom fluid, as well as calculating the solubility constants of the possible incrustants under these conditions.

It was found that the presence

of most of the materials encountered can be predicted.

OPERATION This section incaudes research activities related to the des gn of equipment for handling fluids at the surface and for generating electricity

solving prob-

lems of contamination, recovering valuable materials dissolved in waste fluids, and making use of waste energy, for generating electricity as well as for its possible direct use in indistrial processes.

One of the chief lines of research followed during the last few years has been the optimizing of the design of surface equipment for geothermal use.

These

activities can include the design of the two-leve? arrangement of the steam separators of the plants of Cerro Prieto I1 and 111, which was implemented in order to prevent the vibration problems associated with two-phase fluids.

The

test carried out in well T-388, as well as the performance of the equipment during the time the plant was in operation, confirm the fact that the problem was satisfactorily resolved.

Nevertheless, some doubts remain on the proper

functioning of the ASME steam sampler, for which a group has been formed including CFE and IIE personnel in order to carry out tests for determining the representativity of the sample. As for other fluid handling equipment, a mathematical model has been designed for “U“ type steam separators. Likewise, work is being done in collaboration with CFE on the testing of a number of different types of valves subjected to geothermal field conditions, in order to determine their applicability.

On the

other hand, a review has been made of the operating conditions of silencers at Los Azufres, and the design of those operating at an unacceptable noise level was changed.

A thorough study was undertaken of the the mechanical design of

these units, in order to optimize their efficiency in reducing the noise level, to lower their cost, and to minimize incrustation and mechanical :stress problems. Our FLUDOF computation package for designing lines for two-phase flow is being modified to include the capacity to deallwith problems of confluence of a number of lines.

The work is in the initial stages and still needs to be validated

by observation in the laboratory and in the field.

This matter has been advanced

in the organization of the Second International Seminar on Two-Phase Fluid, which will take place in Cuernavaca in August 1986. In regard to incrustation problems with surface equipment, studies were done to determine what problems could occur in pipes due to waste brine in the high enthalpy wells o f Cerro Prieto I1 and 111.

The separation pressure in the

separators of these planrs was set by taking into consideration the possible occurrence of incrustation. On the other hand, there is currently a study to determine the most efficient method for cleaning silencers and pipes. As for problems of contamination from geothermal wastes, there has been a

series of studies of systems for eliminating, and in some cases recovering, contaminants.

In collaboration with EPRI, there has been a program for testing the

Condenser-Evaporator System for eliminating H S, CO and other noncondensable 2 2

gasses in the steam, before it enters the turbine.

On the other hand, studies

related to el mination of H S using t h e combustion method have been continued. 2

At present, a testing program is being terminated and the design completed of a plant for incinerating the waste gasses of the Cerro Prieto I plant. The second phase of a study of recovery of boron from geothermal brine by using ion-exchanging resins is being completed.

In the first phase the technical

feasibility was established, and the study of the economic aspects was begun.

At present the evidence indicates that, under present economic conditions, the boron recovery process would have economic value if and when there are no degradation effects in the resin, in the Short term. In regard to the use of low enthalpy geothermal fluids, studies have been continued on generation with Rankine organic cycle systems, for which there are two pilot plants (one of 50 KW and the other of 10 KV) installed at Los Azufres. On the other hand, a 30 KWt heat pump has been constructed, and its performance has been evaluated with water at 80°C.

Likewise, 3 ton refrigerator has been

constructed, which would use waste brine as its energy source.

This equipment

is currently in the startup and initial testing stage. Emphasis is being placed on the study of various types of heat exchangers, in order to minimize the problems of incrustation and corrosion associated with the use of geothermal fluids. A study is being completed at the Los Azufres geothermal field to evaluate the effect of these processes on the efficiency of shell-and-tube type exchanges.

The studies have been continued in the laboratory

with a pilot system of a fluidized bed exchanger, in order to define the design:: parameters for a 200 KWt exchanger, which will be tested in the field, in conjunction with the Rankine organic cycle plants.

On the other hand, work is being done

in the design of a heat exchanger capable of using the total flow of a geothermal well, including liquid, steam, and noncondensable gasses.

Once constructed, this

exchanger will be field tested.

A computerized system called

S I G E O has been developed and implemented, which

permits the collection, storage, and reproduction of technieal~lnformationgenerated during the development of geothermal fields.

Los Azufres, La Primavera, and Los Humeros.

Up to now, it has been applied at

SIEGO is applicable to information

generated from the exploration stage to the continuous operation stage.

A s an

example of the kind of information that can be collected and stored, we can mention geological, goechemical, geophysical, and thermodynamic information oktained during drilling, induction, testing, and use of a geothermal well.

SIEGO

has a modular structure, which allows integration of new data modules for processing, for example, information related to materials, replacements, equipment, and economic aspects. At present computational tools are being developed for database use.

These tools provide facilities for graphics in 2 and 3 dimensions;

there are also supporting analytical tools for evaluating geothermal reservoirs. A s an example of the lattep-we can mention:

tools for the interpretation of

injectivity tests and variable flow tests; for obtaining characteristic production curves; for following the evolution of the pressure at the wellhead, the bottom pressure, the bottom temperature, the production of liquid, steam, and mix, etc. A new and important'line of research has been started in regard to the

development of technological capacity in Mexico for the design and manufacture of geothermal turbogenerators.

For this, a plan for transfer of technology has

been implemented, different from the usual one in that the receiving party consists of three entities.

One o f these is the technological institution; in this

case IIE, which will guarantee the complete assimilation of the technology. Another entity is the principal user of the products of this technology; in this case the Comision Federal de Electricidad.

The third entity is a domestic f i r m

which is the final receiver of the technology and will be responsible for the manufacturing and marketing of the turbogenerators.

Technology transfer agpee-

ments have already been made for the design, manufacture, and installtion of 3 ,

5, and 7 MW tubogenerators with the Toshiba company. Most of the abovementioned activities have heen financed by the Gerencia de Proyectos Geotermicos, of the Comision Federal de Electricidad, and the pariticipation.af'its technical personnel has been of vital importance for the proper development of these studies. The writers widh to express their thanks to the heads of the various projects of I I E ' s Geothermal Program, for the information provided.

REFERENCES I g l e s i a s E., Arellano V., Garfias h., mlinar R. y Wanda C. (1985a) "Estimates of the Wservoir Pressure, the Productivity Index, and a ?herma1 €her hroauctivity Index f r m product i o n h t p u t Curves of ceotheml W?lls", mti da a revisi6n a la Sociedad de Ingenieros Petrg leros de AlME (SlJE-AIME), m u s c r i t o SPE-13755. I g l e s i a s R., Arellam V., Garfias A. y Miranda C. (198533). "The N a t u r a l l b e m c d m c S t a t e of the Fluid of IDS Azufres Geothermal Fkservoir". Proc. Tenth Wxkshop on &!othennal Reservoir Engineering, Stanford University, pp 241-246. Arenas A., I g l e s i a s E., Izquierdo G., Guevara M. O l i v e r R. y Santqo S. (1982) " E f f e c t s of O n tamination by Geothermal Drilling Eaal on Labor a t o r y Determinations of Sandstone Pore Properties". Proc. E i g h t Wrkshcp on Geothermal &=wir Engineering, Stanford University, pp 205210. Castaiieda M. y Horne R.N. (1981) "Location of Production 2 0 ~ sw i t h Pressure Gradient Log-

ging". GW Tra~s.5, 275-278. Cathelineau M., O l i v e r R., N i e v a D. y Garfias A. (1985) 'Mineralogy and d i s t r i b u t i o n of hydrothermal m i n e r a l zones in m s kmfres (bSxic0) geothermal f i e l d " Geothermics 1 4 , 49-57.

.

Contreras E. y King M.S. (1985) "Acustic and E l e c t r i c a l -es of Cerro Prieto Core Sanples". Proc. %th Wrkshop on @athermal ~eservDirEngineering, StanfoA ~ v e r s i t y , pp 307-310.

'

Cmtreras E., I g l e s i a s E. y Benoejo F. (1984) ' T a b r a t o r y ~ a s u r e dPhysical Fmperties of Cerro Frieto Rmks. A Review of Early Wxk and Presentation of New Data". GRC Trans. 8 , 193-202,

QCmtreras E.,

I g l e s i a s E. y sdnchez J. (1982a) "Estudios de Penreabilidad a Alta lknperatura de WGcleos de Cerro prieto". hmrias, Cuarto Sinposio Internacional sohre el Campo &!ot&mico de Cerro h-ieto, Guadalajara, A g ~ s t ode 1982.

Cbntreras E., I g l e s i a s E. y F!ernEjo F. (1982b) " E f f e c t s of *atme and Stress on the Corn p r e s s i b i l i t i e s , lhermal Expansivities and Pornsities of Cerro Prieto and Berea sandstones to 9000 p s i and 28OOC". Proc. Eight mrkshop on Geothermal Rxervoir mqineering, stanford University, pp 197-203.

Iglesias E., A r e l l a n , V., Garfias A . , M i r a n d a C . y Arag6n A. (1985~)"A Qle-DhrEnsional V e r t i c a l W l of the IDS mfres, Mkico, Geothermdl Rzervoir in its Natural state". A presentarse en l a Reuni6n Anual de 1985 del Consejo de ReCUTSOS Geot&mims.

I g l e s i a s E., Arellano V. y Mlinar R. (198M) "Steam and Water R e l a t i v e -abilities for the Cerro P r i e t o ceothermdl Weservoir". Proc. Tenth Wrkshop on Ckothemal R e z e r w i r Engineering, Stanford University, pp 301-306. I g l e s i a s E., Garfias A., N i e v a D., Miranda C., Verrna S., C o r m A., m h e z A., cabrera J. and Barrag& R.M. (1985e) '*?he F i r s t rmlti-tracer test in the IDS Azufres Field; Progress Report". h-oc. Tenth on Geothermal Reservoir Engirreering, University, pp 265-272.

multi-11

Geothermal Wrkshop

Stanford

Fplicaci6n a1 AnSlisis de hruebas de R e s i d n para Emluar propiedades de Yacimientos GeOt6.rmicos". "esis de Licenciatura, Facultad de C i e cias, U n i w s i d a d Nacional ht6m de Mkico. Nieva D., Gonzaez J. y Garfias A. (1985) "Evidence of 'Pm Extrem F l m Regims -rating in t h e F'roduction Zones of Different W l l s from IDS Azufres". FTcx. Tenth W r k s b p on Geotherm a l Reservoir Engineering, Stanford University, pp 233-240. &jmo L., Garfias A., Earrag& R.M. Y medo F. (1983) 'T-kterogeneity of the Liquid Phase, and Vapor Separation i n Los Azufres (Wkico) &?oth-l wsenoir". Proc. Ninth Workshop on Geothermdl Reservoir h g i n e ering, S t a n f o r d University, pp 253-260.

Nieva D.,

(1) High Temperature Permeability Studies of Cores from Cerro Prieto. ( 2 ) Hydrodynamic Effects of Storage i n Geothermal

Wells: Application to the Analysis of Pressure Tests for Evaluating Properties of Geothermal Reservoirs.

U.S. DEPARTMENT OF ENERGY PERSPECTIVE Ron Toms

Paper Unavailable a t Time o f Publication

INITIAL OPERATING RESULTS

BLUNDELL GEOTHERMAL 20 MW SINGLE FLASH PLANT

P.O.

Dale R . Brown U t a h Power & Light Company Box 899, S a l t Lake City, Utah (801 ) 535-2264

INTRODUCTION The development of t h e Roosevel t Hot Springs KGRA located in southwestern Utah near Milford i n Beaver County began i n e a r n e s t in 1974 when P h i l l i p s Petroleum obtained a l e a s e and discovered a hydrothermal r e s e r v o i r about 2,000 f e e t from t h e surface with a temperature of 500" Fahrenheit, hot enough f o r commercial production. As previously reported i n e a r l i e r EPRI conferences, Utah Power & L i g h t Company entered i n t o a c o n t r a c t with P h i l l i p s Petroleum f o r t h e purchase of geothermal steam and with t h e i n t e n t of building a 20 MW plant as t h e f i r s t s t e p toward development of t h i s geothermal f i e l d f o r e l e c t r i c power generation. The Blundell Geothermal Plant was recently completed by Utah Power & L i g h t a n d has demons t r a t e d promising i n i t i a l r e s u l t s , i n s p i t e of p a r t i c u l a r operating problems encountered. This paper will focus on the i n i t i a l operating experience of t h e geothermal plant a n d i n d i c a t e the present course of a c t i o n being taken by Utah Power & Light p r i n c i p a l l y , a s well a s P h i l l i p s Petroleum, i n optimizing plant performance. OPERATING SUMMARY The 20 MW Blundell Geothermal Plant has been on l i n e 71 percent of t h e time s i n c e i n i t i a l s t a r t - u p in July 1984. During t h i s time, P h i l l i p s has been a b l e t o provide e s s e n t i a l l y f u l l l o a d steam, making i t p o s s i b l e f o r Utah Power & Light t o produce i n excess of t h e o r i g i n a l 20 MW net r a t i n g . However, t h e s p e c i f i c operating problems, l a t e r described i n d e t a i l , r e s u l t e d in t h e plant only achieving a capacity f a c t o r of 51 percent d u r i n g t h e i n i t i a l nine months of operation time. Most of t h e forced outage time t o d a t e has been caused by turbine s c a l i n g problems a f f e c t i n g t u r b i n e power output l e v e l s and impacting portions of t h e equipment which causes concern f o r short-term a s well a s long-term equipment life. Table I11 summarizes t h e forced and scheduled outages f o r t h e f i r s t ten months of operation. During t h i s i n i t i a l o p e r a t i o n , approximately 104,045,000 KWH energy has been delivered t o Utah Power & L i g h t ' s transmission g r i d . While t h e equipment and system design have been shown t o r e l a t e i n some measure t o t h e nature of t h e problems encountered, we believe c u r r e n t remedial measures being taken

84110

w i l l r e s u l t i n t h i s plant demonstrating a high capacity f a c t o r and o f f e r a viable a l t e r n a t i v e source t o t h e predominantly f o s s i l f i r e d generating capacity employed a t Utah Power & Light. The operating and maintenance c o s t s a r e running a t a r a t e of $1 million per year. PROJECT DESCRIPTION The Blundell Geothermal P l a n t , located 15 miles northeast of Milford in Beaver County, southwestern Utah, i s a s i n g l e f l a s h type geothermal power p l a n t ( s e e F i g ure 1 ) . The 500" Fahrenheit brine i s flashed in wellhead s e p a r a t o r s t o produce steam f o r t h e t u r b i n e . The brine i s then pumped by t r a n s f e r pumps a t each producing well location t o t h e From t h i s brine i n j e c t i o n header l o c a t i o n . brine header l o c a t i o n , a t which a surge tank f o r accommodating t r a n s i e n t flow conditions i s i n s t a l l e d , t h e brine i s then routed t o brine i n j e c t i o n wells located a t t h e o u t e r periphery of t h e r e s e r v o i r . Of t h e t h r e e i n j e c t i o n wells a v a i l a b l e f o r r e i n j e c t i o n of t h e brine i n t o the r e s e r v o i r , one well i s located approximately 2,800 f e e t from t h e brine header surge tank location. The o t h e r two i n j e c t i o n wells a r e located approximately 12,000 f e e t from the brine header surge tank l o c a t i o n . I n j e c t i o n Well 14-2, t h e n e a r e s t of t h e t h r e e i n j e c t i o n w e l l s , u t i l i z e s a v e r t i c a l canned type i n j e c t i o n pump, a s does one of t h e other two w e l l s , Well 12-35. The t h i r d i n j e c t i o n w e l l , Well 82-33, has exhibited i n j e c t i o n c h a r a c t e r i s t i c s w i t h well pressure low enough t o permit g r a v i t y feed i n t o t h e well without requiring t h e use of a n i n j e c t i o n pump. To d a t e , t h e i n j e c t i o n of t h e brine i n t o the system has not required any special measures such as f l a s h c r y s t a l l i z e r s o r c l a r i f i e r s . The only measure taken by P h i l l i p s Petroleum i s t h e use of a s u i t a b l e s c a l i n g i n h i b i t o r t o reduce s c a l i n g in t h e i n j e c t i o n wells. The o t h e r control exercised t o minimize i n j e c t i o n well s c a l i n g i s t o maintain i n j e c t i o n f l u i d temperature a t 275" Fahrenheit o r g r e a t e r . The steam gathering system involving necessary cross country piping from each of t h e f o u r producing wells i s owned and operated by Utah Power & Light w i t h steam delivered by P h i l l i p s Petroleum a s h o r t d i s t a n c e downstream of the

wellhead s e p a r a t o r s . The cross country piping involved i n t h e steam gathering system i s approximately one a n d one-half miles i n length from the f u r t h e s t producing well t o t h e power block. POWER PLANT DESCRIPTION The generating s t a t i o n portion of the p r o j e c t ( s e e Figure 2 ) was designed a s a 23.5 MW gross p l a n t with a heat Performance r a t i n g of 20,100 6tu per KWH. t e s t s indicate that the plant i s able t o produce t h e 23.5 MW gross a n d with a heat r a t i n g of 20,080 B t u per KWH a t design The p a r t i c u l a r combination of conditions. wells used, both production and i n j e c t i o n , a f f e c t s t h e plant a u x i l i a r y l o a d and t h e corresponding net p l a n t output. Under optimum p l a n t equipment conditions, t h e p l a n t has delivered a s high as 21.4 MW net t o t h e t r a n s mission g r i d . The steam was expected t o have a maximum of 5 ppm TDS and a pH of 7.0. Consequently, 300 s e r i e s s t a i n l e s s s t e e l was used The actual steam dethroughout the plant. l i v e r e d has approximately 0.7 ppm TDS w i t h a pH of approximately 4.0. Table I summarizes t h e equipment and materials in construction. Table I1 summarizes t h e chemical p r o p e r t i e s of the steam and noncondensible gas systems. The plant was designed f o r removal of u p t o 3 percent noncondensible gas. However, the t y p i c a l values have been 2.5 percent o r l e s s so f a r , The trend observed r e f l e c t s an increase i n t h e concentration of H,S from 2,000 ppm t o about 3,000 ppm. A t t h e same time, the noncondensible gas percentage of steam has decreased s u b s t a n t i a l l y from each of t h e producing wells ( a s low a s .3 ppm). INITIAL OPERATING PROBLEMS P r i o r t o t h e actual s t a r t - u p of t h e p l a n t for commercial operation, t h e major equipment problems encountered involved t h e brine t r a n s f e r and b r i n e i n j e c t i o n pumps i n s t a l l e d near t h e producing wells and t h e brine i n j e c t i o n header l o c a t i o n r e s p e c t i v e l y . These pumps were a l l v e r t i c a l canned type pumps and experienced s i m i l a r problems involving excessive v i b r a t i o n and undue f a i l u r e of t h e mechanical s e a l s used on t h e pump s h a f t s . Considerable e f f o r t has been undertaken t o improve pump performance involving evolution i n t h e design of t h e mechanical s e a l s used. We presently employ double s e a l s with a Dowtherm high temperature heat t r a n s f e r f l u i d used a s a s e a l coolant. Operating experience has enabled us t o minimize t h e v i b r a t i o n problems and improved seal l i f e has been realized by changes in the s e a l design as mentioned previously, b o t h in m a t e r i a l s involved i n the seal faces and in the design of t h e seal f o r proper heat t r a n s f e r from the seal f a c e s t o t h e coolant

f l u i d . We have a l s o added a d d i t i o n a l cooler capacity on the seal cooler systems with up t o t h r e e coolers in a s e r i e s on t h e b r i n e i n j e c t i o n pumps.

A t p r e s e n t , we a r e looking t o i n s t a l l one horizontal pump a s a replacement f o r one of t h e four brine t r a n s f e r pumps. I t i s hoped t h a t t h i s pump w i l l a f f o r d us some improved pump l i f e and have t h e advantages inherent in such a pump, including o i l lubricated bearings r a t h e r t h a n t h e product l u b r i c a t e d bearings. Shortly following i n i t i a l s t a r t - u p of the p l a n t in July 1984, problems were encountered with t h e main control valve i n t h e steam supply l i n e This i s a Vanessa b u t t e r f l y t o t h e turbine. valve provided as a p a r t of the General Elect r i c turbine-generator system. The s e a l i n g ring material on t h e valve was i n i t i a l l y 316 SS m a t e r i a l , and t h e r e was a deformation phenomenon experienced causing t h e valve t o s t i c k in t h e closed p o s i t i o n . This problem was resolved by changing t h e seal ring t o a u s t e n t i c - f e r r i t i c s t e e l and a reduction in t h e closing f o r c e applied t o t h e valve. We have had no problems with t h e control valve since t h a t change was implemented. As indicated previously, t h e i n i t i a l operating

experience on t h e t u r b i n e was a s expected, with s u f f i c i e n t steam supplied t o achieve the r a t e d gross output of 23.5 MW. Commercial operation of t h e p l a n t was declared on July 31 , 1984, and the t u r b i n e generator and associated equipment performed without problems f o r several months. After a period of time, a number o f operating a n d maintenance problems were manifested. The most c r i t i c a l of these was t h e formation o f s c a l e on t h e General E l e c t r i c turbine. A t t h i s p o i n t , we made t h e decision t o shut t h e u n i t down f o r inspection. Turbine inspection revealed s i g n i f i c a n t s c a l e d e p o s i t i o n , p a r t i c u l a r l y in t h e f r o n t t u r b i n e steam s e a l s and t h e f i r s t s t a g e diaphragm nozzles. Analysis of s c a l e samples taken from t h e t u r b i n e indicated v a r i a b l e high l e v e l s of both sodium c h l o r i d e and s i l i c o n dioxide, depending on the o r i g i n of the sample taken. I t was a l s o apparent a t t h e time t h a t t h e severe s c a l i n g in the seal area resulted in erosion of the steam seal labyrinth surfaces. During the turbine shutdown f o r inspection, t h e steam s e a l s were refurbished and the t u r b i n e r o t o r a n d diaphragms were sandblasted t o remove scale deposits. During t h i s p l a n t outage, modifications were a l s o made- t o t h e knockout drum and one of the wellhead separators. A b a f f l e p l a t e in t h e wellhead s e p a r a t o r was lowered and a new i n t e r n a l c o l l a r was added t o These modifications were t h e knockout drum. intended t o improve the steam p u r i t y a n d quality.

As a r e s u l t o f t h e t u r b i n e s c a l i n g problem, a team was formed c o n s i s t i n g o f p e r s o n n e l f r o m Utah Power & L i g h t , P h i l l i p s Petroleum, EPRI, and B e c h t e l Group, I n c . T h i s group was formed t o c o n d u c t a f i e l d t e s t program i n t e n d e d t o o b t a i n chemical d a t a on t h e steam g a t h e r i n g system. The key chemical s p e c i e s t r a c k e d d u r i n g t h e t e s t i n g i n c l u d e d sodium c h l o r i d e and silica. The chemical d a t a f r o m t h e t e s t program (as shown i n F i g u r e s 3, 4, and 5 ) i n d i c a t e d t h a t t h e p u r i t y and q u a l i t y o f t h e steam f e e d t o t h e t u r b i n e was more t h a n adequate based on t h e o p e r a t i n g e x p e r i e n c e s o f s i m i l a r geothermal power p l a n t s . A t geothermal power p l a n t s i n C e r r o P r i e t o , Mexico and W a i r a k e i , New Zealand, t h e power c a p a c i t y l o s s e s have been l e s s t h a n t e n p e r c e n t o v e r a two-year p e r i o d when maint a i n i n g steam p u r i t i e s a t l e s s t h a n 100 ppb s i l i c a and l e s s t h a n 5 ppm TDS i n t h e f e e d t o the turbine. D u r i n g t h e f u l l l o a d and p a r t i a l l o a d t e s t i n g a t B l u n d e l l Geothermal, t h e steam q u a l i t y was g r e a t e r t h a n 99.95 p e r c e n t , t h e TDS was l e s s t h a n 1 ppm, and t h e s i l i c a c o n t e n t was l e s s t h a n 100 ppb. A l s o , t e s t r u n s a t p l a n n e d upset conditions during t h e t e s t i n g d i d not measurably degrade e i t h e r t h e q u a l i t y o r p u r i t y of t h e steam f e e d t o t h e t u r b i n e . The t u r b i n e performance t e s t s conducted a t t h e turbine manufacturer's design conditions i n d i c a t e d t h a t o v e r t h e six-week t e s t program p e r i o d , measurable t u r b i n e performance degradat i o n was o c c u r r i n g . A l t h o u g h a maximum g r o s s o u t p u t o f 23.7 MW c o u l d be a t t a i n e d a t t h e o n s e t o f t h e t e s t program, t h e maximum o u t p u t d e c l i n e d t o 21.6 MW by t h e end o f t h e t e s t a f t e r a p p r o x i m a t e l y 22 days o f noncontinuous turbine operation.

A t t h e end o f t h e t e s t , t h e t u r b i n e f r o n t bowl c o v e r was removed t o a l l o w i n s p e c t i o n o f t h e f r o n t steam s e a l s and t h e f r o n t s i d e o f t h e f i r s t s t a g e diaphragm. Inspection revealed some s c a l e f o r m a t i o n on t h e diaphragm n o z z l e s and s u b s t a n t i a l s c a l e f o r m a t i o n i n t h e steam s e a l area. A n a l y s i s o f t h e s c a l e samples f r o m t h e t u r b i n e i n d i c a t e d t h a t t h e steam s e a l d e p o s i t s a r e a p p r o x i m a t e l y 90 p e r c e n t sodium c h l o r i d e and t h a t t h e f i r s t s t a g e diaphragm d e p o s i t s a r e a p p r o x i m a t e l y 85 p e r c e n t s i 1 i c a ( c o m p o s i t i o n s s i m i l a r t o t h e s c a l e samples c o l l e c t e d d u r i n g t h e p r e v i o u s December 1984 turbine inspection). Despite the f a c t t h a t the o v e r a l l p u r i t y o f the steam t o t h e t u r b i n e i s s a t i s f a c t o r y (compared t o o t h e r s i m i l a r geothermal power p l a n t s ) , s i g n i f i c a n t scale formation inside the turbine o c c u r r e d on t h e steam s e a l s and f i r s t s t a g e diaphragm n o z z l e s . A l t h o u g h t h e o v e r a l l steam p u r i t y i s c o n s i d e r e d h i g h (as measured by condensing n e a r l y a l l o f a steam sample and analyzing the l i q u i d fraction f o r specific i o n s , such as sodium), i t l i k e l y t h a t some moisture d r o p l e t s o r i g i n a t i n g from the b r i n e

v i a entrainment a t t h e wellhead remain i n t h e steam t o t h e t u r b i n e .

separators

Because t h e p r e s s u r e drops i n t h e t u r b i n e a c r o s s t h e steam s e a l s and f i r s t s t a g e d i a phragm a r e r e l a t i v e l y h i g h (approximately 95 p s i a c r o s s t h e steam s e a l and 45 p s i a c r o s s t h e f i r s t s t a g e b l a d e n o z z l e ) , any d r o p l e t s o f m o i s t u r e suspended i n t h e steam w i l l t e n d t o evaporate. During s u f f i c i e n t evaporation, d i s s o l v e d s p e c i e s , such as sodium c h l o r i d e and s i l i c a , w i l l a t t a i n saturation i n the moisture d r o p l e t s , t h u s d r o p p i n g o u t o f s o l u t i o n and d e p o s i t i n g s c a l e on l o c a l i z e d areas i n s i d e t h e turbine. Given t h e r e s u l t s observed i n t h i s t e s t i n g e f f o r t , two b a s i c c o u r s e s o f a c t i o n have been i n i t i a t e d t o improve t h e q u a l i t y and p u r i t y o f t h e steam. One o f t h e measures t a k e n i s t o d e s i g n and i n s t a l l secondary steam c l e a n i n g equipment t o be i n s t a l l e d downstream o f t h e e x i s t i n g knockout drum. A t the present time, t h e t y p e o f secondary steam c l e a n i n g e n v i s i o n e d i s a c o m b i n a t i o n o f a hook and vane t y p e d e m i s t e r i n c o n j u n c t i o n w i t h a packed bed s c r u b b e r . The arrangement o f t h i s i n s t a l l a t i o n between t h e knockout drum and t h e t u r b i n e b u i l d i n g i s shown i n F i g u r e 6. I n a d d i t i o n t o t h e i n s t a l l a t i o n o f t h e second a r y steam c l e a n i n g equipment, a program has been i n i t i a t e d t o m o d i f y t h e e x i s t i n g steam t r a p s i n s t a l l e d on t h e c r o s s c o u n t r y steam g a t h e r i n g p i p i n g system, as w e l l as t o add a d d i t i o n a l steam t r a p s . Presently, there are 16 steam t r a p s i n s t a l l e d between t h e p r o d u c i n g w e l l s and t h e t u r b i n e b u i l d i n g . As i n d i c a t e d , t h e s e e x i s t i n g t r a p s w i l l be m o d i f i e d t o improve t h e i r performance, b a s i c a l l y t h r o u g h i n c r e a s i n g t h e steam t r a p body d i a m e t e r and increasing i t s length. I n addition, the e f f o r t w i l l include the a d d i t i o n o f 25 a d d i t i o n a l steam t r a p s a l s o of t h i s l a r g e r d i a m e t e r and i n c r e a s e d depth, appropriately placed along the cross country steam p i p i n g system t o enhance t h e removal of m o i s t u r e f r o m t h e steam and, a t t h e same t i m e , remove a s u b s t a n t i a l p o r t i o n o f t h o s e p a r t i c l e s e n t r a i n e d i n t h e steam which a r e a f f e c t i n g steam p u r i t y . The e f f o r t t o i n s t a l l a d d i t i o n a l steam t r a p s and t o m o d i f y e x i s t i n g steam t r a p s w i l l be l a r g e l y accomplished a t an annual shutdown f o r maintenance and o v e r h a u l i n J u l y 1985. The secondary steam c l e a n i n g equipment, c o n s i s t i n g o f t h e hook and vane d e m i s t e r and packed bed s c r u b b e r , i s scheduled f o r i n s t a l l a t i o n l a t e r on. A t t h i s t i m e , we a n t i c i p a t e t h e hook and vane d e m i s t e r t o b e i n s t a l l e d i n i t i a l l y f o r t e s t purposes i n m i d October. Depending upon t h e r e s u l t s a c h i e v e d i n i m p r o v i n g steam p u r i t y and q u a l i t y , as r e f l e c t e d by reduced s c a l i n g w i t h i n t h e t u r b i n e , we may e l e c t t o e l i m i n a t e t h e i n s t a l l a t i o n o f t h e packed bed s c r u b b e r .

In t h e interim, we have been concerned in the s h o r t term more w i t h t h e impact o f s c a l e build-up in t h e s h a f t steam seal a r e a . We can t o l e r a t e t h e b u i l d - u p of s c a l e on the diaphragm nozzles and turbine blades with the correspondi n g power reduction without short-term concerns of possible damage t o t h e equipment. However, experience t o d a t e shows t h a t we could not operate the t u r b i n e f o r long periods without causing permanent damage t o t h e s t e e l s h a f t by allowing the build-up i n t h e steam seal area t o be excessive. Accordingly, we have adopted t h e p r a c t i c e o f f a i r l y frequent short-time duration shutdown i n t e r v a l s t o permit cleaning of t h e s h a f t and t h e l a b y r i n t h type s e a l s t o remove t h e build-up of s c a l e in t h a t area. While t h i s has impacted our O&M c o s t s , we expect t h a t t h e remedial action taken t o add t h e secondary steam cleaning equipment and the modification t o t h e steam trap system will minimize t h e s c a l e build-up throughout t h e t u r b i n e , including the steam s e a l area. This w i l l enable us t o operate the t u r b i n e f o r longer periods of time and lower our 0&M c o s t s t o l e v e l s t h a t we can t o l e r a t e in t h e long run. As indicated previously, i t i s expected t h a t solving these equipment problems will r e s u l t i n Blundell Geothermal demonstrating s a t i s f a c t o r y performance and o f f e r i n g a v i a b l e a1 t e r n a t i v e source t o t h e predominantly f o s s i l fuel f i r e d generating capacity presently employed a t Utah Power & Light Company.

BLUNUtLL GEOTHERMAL 20 MW SINGLE FLASH PLANT

-

CONDENSER

J I

COOLING TOWER

-

WELL 13-10

+-

F-r-

R 4 WELL 54.3

INJECTION WELLS

Steam P r o d u c t i o n F a c i l i t i e s by P h i l l i p s Petroleum

Generating S t a t i o n by Utah Power & L i g h t Company Figure 1

INTE RCONDLNSE R AFTERCONDEN

MAIN CONDENSER LUBE OIL COOLERS

I 4

1

E M COOLERS

COOLINQ TOWLR

W A C CONDENSER

-5Y CDNDENSATE PUMPS

AUX. COOLIN0 WATER PUMPS

Fiqure 2 Generation S t a t i o n System Diagram

-

IJ

I

Figure 3

Anderson Knock-Out

D r u m Outlet S t e a m

Estimated Steam Quality

100

0

99 .99.5

m

0 3

99.99

0 0

0 0

99.985

0

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99.98

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99.96

0 0

99.955

I

8

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10

I

I

12

I

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14

I

I

16

1

1

18

P o w e r Plant Load, MWe

1

1

20

1

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Figure 5

Drum I n l e t S t e a m

Anderson Knock-Out

Sodium Content

0.8

0

0.7

0

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0

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E

0

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16 18 Power Plant Load, MWe I

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24

NEW PACKED SCRUBBER TOWER

PRESENT AN DERSON KNOCK-OUT

NEW FINAL MOISTURE REMOVAL VOOK & VANE

-

STEAM TO TURBINE

WATER

STEAM CONDENSER %

RECYCLE PUMP

MAKE-UP FROM STEAM CONDENSATE

Schematic of Secondary Steam Cleaning Facility Figure 6

I

TABLE I EQUIPMENT DESCRIPTION BLUNDELL GEOTHERMAL 20 MW SINGLE FLASH PLANT

Equipment

Make

Knockout Drum

, ..iderson

Steam Turbine/Generator

General E l e c t r i c

Condenser

Ecolair e

C o o l i n g Tower

P r itchard

Main Steam P i p i n g Condensate P i p i n g

Description and M a t e r i a l

Rating

5

ss

23.5 MW

3 7 2 ~ 1 0B~t u / h r 30,600 GPM

24-30",

150 l b

36", 150 l b

21

-CS,

Internals-304L

7 Stage-impulse type, 12% CR b l a d e s D i r e c t Contact 4 C e l l , Crossflow 110°-82"FA (3 67°F WB, PVC fill, d r i f t eliminator ASTM A53-Gr. 316 s t a i n l e s s

BCS

CHEMICAL PROPERTIES GEOTHERMAL FLUIDS--BLUNDELL GEOTHERMAL PLANT

Property

Brine (ppm)

Turbine Steam

N / C Gas

115 psia

Pressure

338°F

Temperature

125°F

.4%

NIC Gas

97.1%

c02

.14%

N2

.014%

02

39 PPm

He

25 P P ~

HZ

3,000 ppm

"ZS

Boron

31

Calcium

10

Magnesium

0.01

Potassi um

47 0

Sodi urn

2,200

3.4 ppm

Silica

520

.9 PPrn

Ammonium

145

1.44 ppm

Chloride

3,900

Nitrate) Nitrite )

75.1

Sulfate Iron

21 1 110 ppb

TABLE I11 OUTAGES BLUNDELL GEOTHERMAL 20 MW SINGLE FLASH PLANT

Forced Outages August 1984-May 1985 P h i l l i p s P e t r o l e u m Steam Supply G e n e r a t i n g S t a t i o n / B r i n e Pumping Equipment

12 h o u r s 152 h o u r s 164 h o u r s

Total

Scheduled Outages August 1984-May 1985 R o u t i n e T u r b i n e Maintenance, I n s p e c t i o n s , and C l e a n i n g

R&D T e s t Total

1,608 h o u r s 334 h o u r s 1,942 h o u r s

THE FIVE UNITS OF CERRO PRIETO I Fernando Ledezma

Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n

SALTON SEA 10 MWe S I N G L E FLASH PLANT

E l g i n Moss

3

sCf5

Paper U n a v a i l a b l e a t Time o f P u b l i c a t i o n

OPERACION DE EQUIPOS DE SUPERF'ICIE PARA LA RECOLECCION DE

FLUIDOS GEOTERMICOS EN CERRO PRIETO I

Alfredo Ma?&, Francisco Bermejo, Pedro P&ez

RESUMEN

En Cerro P r i e t o I s e han generado 10 millones de MWh y s e han producido

300 millones de toneladas de f l u i d o geot6rmico.

La longitud de l a red-

a c t u a l de t u b e r l a s de vapor con di6metro de 12 a 40 pulgadas, e s de 24,000 m.

- -

La red de t u b e r f a s de agua con di6metros de 8 a 16 pulgadas-

e s de 46,500 m.

Est&

en operacidn 32 pozos, 4:

separadores, 58 s i l e n -

b ciadores, 7 secadores de vapor y 290 vhlvulas de 8 a 30 pulgadas de d i -

metro.

La corrosi6n en l a s t u b e r i a s y equipos s u p e r f i c i a l e s no ha sido

un problema grave.

-

E l p r i n c i p a l problema de mantenimiento ha sido l a

limpieza de l a s incrustaciones y sedimentos de s l l i c e en t u b e r f a s , equi -

pes y canales.

Frecuente mantenimiento es necesario para conservar l a -

capacidad de l a s tuberfas de agua, de 10s separadores y de 10s canales. Las t u b e r i a s de 10s pozos y en algunos casos e l yacimiento mismo, tam-bien han s i d o afectados por las i n c r u s t a c i o n e s .

Aiin l a s pequefias

c a n ti

dades de s i l i c e que s e a r r a s t r a n en el vapor separado originan dep6si-t o s en las turbinas disminuyendo s u capacidad.

Durante e l tiempo que s e t i e n e operando l a Central de Cerro P r i e t o I ,

-

se han e x t r a i d o d e l yacimiento m6s de 150,000 toneladas de s f l i c e d i s u el t a e n e l agua, de l a s cuales una pequefia cantidad s e deposita en tuberfas, equipos y canales; descarggndose l a mayor p a r t e en l a laguna de evaporacidn.

OPERACION DE EQUIPOS DE SUPERFICIE PARA LA RECUPERACION DE FLUIDOS GEOTERMICOS EN CERRO P R I E T O I

Alfred0 Mafidn, Francisco Bermejo, Pedro PdreZ Comisidn Federal de E l e c t r i c i d a d Apartado P o s t a l 3-636 Mexicali, B . C . 21000 l ( 7 0 ) 656-35142

INTRODUCCION La Central Geotermoeldctrica de Cerro P r i e t o I t i e n e cinco unidades; c u a t r o de L a s dos primeras uni37.5 MW y una de 30 MW. dades i n i c i a r o n s u operaci6n en 1973, l a s unidades 3 y 4 en 1979 y l a unidad N o . 5 e n 1981. L a e n e r g i a e l g c t r i c a producida por l a s c i n c o unidades h a s t a e l mes de diciembre de 1984 f u e Esa e n e r g i a e l d c t r i c a f u e produde 9593 GWH. c i d a con 100 millones de t o n e l a d a s de vapor -geot&mico y e s t e vapor f u e producido con 334millones de t o n e l a d a s de mezcla. E l c a l o r ext r a i d o f u e de 107,000 t e r a c a l o r i a s . E l consumo e s p e c i f i c o de c a l o r geotdrmico p o r Kwh gene rad0 ha permanecido o menos c o n s t a n t e . En l a Tabla No. 1 se muestran 10s v a l o r e s anuales. La disminuci6n de generaci6n observada e n 1980 y 1981 se deb16 a problemas en l a s t o r r e s de enfriamiento.

mss

En l a Tabla N o . 2 s e muestra l a r e l a c i d n de -10s pozos que actualmente proveen de vapor a l a C e n t r a l de Cerro P r i e t o I , y las principa-l e s c a r a c t e r i s t i c a s de 10s mismos. En l a Fiqura No. 1 s e muestra l a l o c a l i z a c i d n de 10s pozos y de las t r e s C e n t r a l e s . L a profundidad de 1 0 s pozos que alimentan de vapor a l a Cen-La t r a l de C P - I , v a r i a e n t r e 1 2 1 2 y 2567 m. p r e s i 6 n e n l a cabeza v a r i a de 58 h a s t a s o l o -6.3 kg/cm2 m. E l rango de l a p r e s i d n de sepaLa produc-r a c i 6 n v a r i a de 8.4 a 6 kg/cm2 m. ci6n de vapor o s c i l a e n t r e 13 y 89 toneladas/hora y l a e n t a l p i a e n t r e 1116 y 2500 Kj/kg. La p r i n c i p a l e x p l i c a c i d n de l a s grandes dife-r e n c i a s en produccidn, en e n t a l p i a y p r e s i d n en l a cabeza e s l a profundidad a l a que s e enc u e n t r a produciendo cada pozo; en g e n e r a l lospozos m 6 s profundos explotan formaciones m 6 s p o t e n t e s que 10s pozow someros. En l a Tabla No. 3 s e muestran l a s c a r a c t e r i s t i c a s promedio mbs importantes de 10s pozos de C P - 1 , C P - I 1 yCP-111. Como s e puede o b s e r v a r , l a profundi-dad, l a e n t a l p i a , l a temperatura y e l contenido de s d l i d o s d i s u e l t o s e n e l cas0 de C P - I son 10s menores. E l contenido promedio de gases incondensables en el vapor separado de CP-I es mayor que e l contenido promedio en C P - I 1 y CP111, l o c u a l s e e x p l i c a por l a menor profundidad a l a que s e e x p l o t a e l yacimiento de C P - I , e n donde se acumula mayor cantidad de gases. En l a Tabla No. 4 s e muestra l a composicidn -quimica de 15 pozos r e p r e s e n t a t i v o s de CP-I yen l a Tabla No. 5 s e muestra en forma d e t a l l a da l a composicidn quimica y algunas propieda-des f i s i c a s d e l agua separada en c u a t r o pozos,

de 10s cuales 10s t r e s primeros corresponden a l a zona de CP-I. E l contentdo de s i l i c e en e l aqua separada a

-

l a p r e s i 6 n atmosfdrica v a r l a e n t r e 693 y 1308a l t o de s d l i d o s t o t a l e s d i mg/l; el v a l o r s u e l t o s (STD) e s de 41,624 y e l mbs b a j o es de 13,413 mg/l.

mss

En l a Tabla N o .

6 s e muestra e l a n 6 l i s i s quimL E l a l t o COG t e n i d o de gases en e l pozo M-104 (3.4% e n pe-s o ) s e puede e x p l i c a r p o r l a profundidad a l a que s e encuentra l a e n t r a d a de f l u i d o a1 pozo(1275 m ) , que e s l a m 6 s somera de l a p a r t e d e l yacimiento l o c a l i z a d o a 1 E s t e de l a v i a d e l f g r r o c a r r i l ; e s t 0 e s , inmediatamente abajo de -una formaci6n de muy b a j a permeabilidad v e r t i cal.

co d e l vapor separado en 7 pozos.

2 s e muestran l a s c a r a c t e r i s t i c a s de producci6n o r i g i n a l e s , ( p r e s i 6 n en l a cabeza vs. producci6n de mezcla) de dos pozosde CP-I. L a d i f e r e n c i a en l a produccidn s e d e be a que e l primer0 produce d e l yacimiento que s e encuentra e n t r e 1058 y 1266 m. y e l segundo E S t a Gltima formacidn con de 1702 a 1946 m. mayor p o t e n c i a l de produccidn que l a primera. En l a Figura NO.

-

En l a Figura No. 3 s e muestra en forma esquems t i c a , e l sistema de t r a n s p o r t e de vapor y agua p a r a l a C e n t r a l de Cerro P r i e t o I , en donde se puede observar l a s t r e s e t a p a s de evaporacibns e p a r a c i h , con l a s que s e o b t i e n e e l vapor de a l t a , media y b a j a p r e s i 6 n p a r a l a s c i n c o u n i dades de l a C e n t r a l de CP-I. La red de t u b e r f a s que conducen e l vapor separado de cada pozo a l a C e n t r a l s e muestra en l a Figura N o . 4. E l c r i t e r i o empleado p a r a e l t r a n s p o r t e de vapor ese l de conectar t u b e r i a s "alimentadoras" a los"ramales p r i n c i p a l e s " , p o r 10s c u a l e s se condc c e e l vapor h a s t a l a C e n t r a l . En l a Tabla No. 7 s e muestra l a r e l a c i d n de pozos que alimen-t a n a cada ramal p r i n c i p a l y l a cantidad de v a por que s e t r a n s p o r t a por cada uno. La compos i c i d n quimica d e l vapor s e muestra e n l a Ta-b l a No. 6 CONDUCCION DE VAPOR

Los dismetros de l a s t u b e r i a s empleadas son de 1 2 a 40 pulgadas, predominando l a s t u b e r f a s de 18, 16 y 32 pulgadas. La l o n g i t u d t o t a l de las t u b e r i a s de vapor e s de 24240 m. (Tabla No.

--

E l peso de l a s t u b e r i a s de aqua y vapor i n s t a l a d a s en CP-I es de 6553 toneladas.

8).

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La operaci6n de l a r e d de t u b e r i a s de vapor h a s i d o s e n c i l l a y f b c i l s u mantenimiento. Las purgas de condensado son l a s 6nicas p a r t e s d e l sistema de t r a n s p o r t e de vapor que r e q u i e r e n de mayor cuidado y mantenimiento, p o r e l c a r d 5 t e r e r o s i v o de l a mezcla aqua-vapor a elevadavelocidad e n l a s puryas (codos) de 2 pulgadas. En l a Figura N o . 6 se muestra una de l a s pur-gas que se encuentran i n s t a l a d a s a i n t e r v a l o s La funr e g u l a r e s e n 10s ramales p r i n c i p a l e s . ci6n de e s t a s purgas e s muy importante ya quepermite l a eliminaci6n d e l condensado y sobretodo de l a salmuera que s e a r r a s t r a en e l va-por. La c a l i d a d normal d e l vapor separado a l a s a l i d a de 10s separadores i n s t a l a d o s en cada pozo, e s de 99.995%; l a d i f e r e n c i a 0.005% es salmuera que s e debe e x t r a e r por l a s purgas. Adem& e s t a s purgas han s e r v i d o p a r a " a t r a p a r " 10s s 6 l i d o s a r r a s t r a d o s p o r e l vapor separadocomo dxidos y s u l f u r o s met6licos, y a6n arenaproveniente de 10s pozos, e n c i e r t o s casos. Antes d e u t i l i z a r l a s purgas t a l como e s t & en l a Figura No. 6 , s e u t i l i z a r o n trampas de va-p o r convencionales d e l t i p 0 cubeta i n v e r t i d a en l u q a r d e o r i f i c i o s , s i n haberse obtenido r e s u l t a d o s s a t i s f a c t o r i o s , por l o que fueron - s u b s t i t u i d o s por e l a r r e g l o a c t u a l que, aunque permite c i e r t o d e s p e r d i c i o de vapor, asegura l a eliminaci6n d e l condensado y l a salmuera. La c o r r o s i 6 n en e l i n t e r i o r de 10s vaporductos h a s i d o minima y se estima que e s d e l mismo va l o r que e l medido d u r a n t e pruebas de corrosi6; l l e v a d a s a cab0 en 1977 y que r e s u l t 6 en e l -rango d e 0.014 a 0.030 mm/afio. En l a Tabla -No. 9 s e muestran 10s espesores de l a pared de 10s ramales p r i n c i p a l e s que fueron medidos a 600 m. a n t e s de l l e g a r a 10s c o l e c t o r e s de l a Como s e puede v e r en e s t a t a C e n t r a l de C P - I . b l a , 10s espesores en l a p a r t e i n f e r i o r de l a s tuberias son en g e n e r a l menores que en l a s posiciones superior y laterales. Utilizando val o r e s promedio de 10s e s p e s o r e s , asumiendo que no s e ha presentado c o r r o s i 6 n en l a s o t r a s pos i c i o n e s , s e estim6 que l a velocidad de corros i 6 n en l a p a r t e i n f e r i o r de l a tuberia es de0.021 mm. p o r aiio. Una buena p r b c t i c a que hae v i t a d o l a c o r r o s i 6 n excesiva en e l i n t e r i o r de l a s t u b e r i a s de vapor ha s i d o e l mantener p r e s u r i z a d a s l a s t u b e r i a s , siempre que s e a pos i b l e , evitando l a e n t r a d a de a i r e a las m i s - mas, cuando no e s t & operando. En l a Tabla N o . 10 aparecen l a s c a i d a s de pres i 6 n que se t i e n e n en algunos de 10s pozos mbs a l e j a d o s de l a C e n t r a l , en donde se puede ob-Servar que l a mayor c a i d a de p r e s i 6 n e s de 2.6 kq/cm2 y l a menor e s de solo 0.2 kq/cm2. La t u b e r i a de mayor l o n g i t u d por l a c u a l s e ha -t r a n s p o r t a d o vapor f u e de 3680 m. correspon--d i e n t e a1 pozo M - 1 0 1 . Todas l a s t u b e r i a s de aqua y vapor t i e n e n a i s lamiento tgrmico; e l d r e a c u b i e r t a con a i s l a - -

miento e s de 96,000 m2. Originalmente s e emplearon colchonetas de f i b r a de v i d r i o soport a d a s con t e l a de g a l l i n e r o y r e c u b i e r t a s con cemento monolftico. E l problema observado -con e s t e t i p o de recubrimiento es que no t i e ne l a s u f i c i e n t e r e s i s t e n c i a n i f l e x i b i l i d a d para s o p o r t a r l a degradacibn d e l medio amble? te. Por e s t a s razones, a p a r t i r de l a s unidades 3 y 4 se cambi6 e l t i p 0 d e recubrimiento c o l o cando en l u y a r de cemento monolitico, lbminade aluminio, l a que ha dado mejores r e s u l t a - dos durante 10s 6 aiios que t i e n e i n s t a l a d a . En l a Figura N o . 5 s e muestran alqunos t i p o s de s o p o r t e s u t i l i z a d o s en l a s t u b e r i a s de vapor. Originalmente se u t i l i z a r o n r o d i l l o s SO b r e p l a c a s de a c e r o a 1 carb6n (Fiyura N o . 5b), per0 no s e continuaron empleando por 10s problcmas que presentaron de c o r r o s i 6 n y contami naci6n de t i e r r a y p i e d r a s por s u posici6n a i n i v e l d e l t e r r e n o . Posteriormente s e emple6o t r o t i p 0 de s o p o r t e (Figura N o . 5b) que qued6 suficientemente separado d e l n i v e l n a t u r a l d e l t e r r e n o , per0 que por 10s problemas obser vados para mantener en s u posici6n o r i g i n a l 2 l a p l a c a de t e f l 6 n y p o r e l mayor c o s t o de -10s m a t e r i a l e s , s e de16 de u t i l i z a r . Final-mente s e adoptaron s o p o r t e s como e s de l a Fien 10s que gura N o . 5c o v a r i a n t e s de &e, se ha s i m p l i f i c a d o e l disefio evitando p a r t e s m6viles. L a forma de absorber l a s d i l a t a c i o n e s ha s i d o

empleando "curvas de expansi6n" de %nqulo r e g t o , h o r i z o n t a l e s en e l drea de pozos y v e r t i c a l e s d e n t r o de l a Central p o r razones de e5 patio y para p e r m i t i r c i r c u l a c i 6 n de vehlcu-10s.

Cada t u b e r i a "alimentadora" t i e n e una vhlvula de c o r t e a n t e s de c o n e c t a r s e a 1 ramal respect i v o , y una p l a c a de o r i f i c i o p a r a medicidn d e l caudal de vapor. Para e v i t a r e l a r r a s t r e de aqua se t i e n e una v6lvula pr6xima a l a d e s carga de vapor de cada separador que a1 inmd a r s e , e l f l o t a d o r e s f 6 r i c o que t i e n e en e l i n t e r i o r , b l o q u e a e l paso de aqua y vapor a l a red de t u b e r i a s y finalmente a l a s t u r b i n a s . En cas0 de que esta vdlvula no o p e r a r a , se dispone de una protecci6n en 10s secadores de vapor de l a C e n t r a l , que c i e r r a n las v h l v u l a s de par0 a l a e n t r a d a de l a s t u r b i n a s cuando Tambign s e e l n i v e l de aqua e s muy a l t o . nen i n s t a l a d o s dos d i s c o s de r u p t u r a con d i f e r e n t e ranqo de operaci6n, como medio de pro-t e c c i 6 n d e l separador y de l a s t u b e r i a s a l i - mentadoras (Figura N o . 1 5 ) . Uno de 10s d i s - COS de r u p t u r a t i e n e i n s t a l a d a una vdlvula de c o r t e que normalmente se encuentra a b i e r t a yque permite e l f b c i l reemplazo d e l d i s c o , dejando p r o t e g i d o e l separador con e l segundo d i s c o que no t i e n e vdlvula de c o r t e . Origi-nalmente (Fiqura N o . 14) s e emplearon v%lvu-l a s de seguridad e n l u g a r de d i s c o s de ruptur a , per0 debido a 10s problemas de corrosi6n-

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y m a l funcionamiento, s e eliminaron y s e subst i t u y e r o n por 10s d i s c o s de r u p t u r a a n t e s desc r i t o s . Un problema no muy f r e c u e n t e que s e ha t e n i d o con 10s d i s c o s e s que en ocasiones operan a p r e s i o n e s muy i n f e r i o r e s a l a s de d i sefio, l o c u a l s e e x p l i c a por l a p r e s e n c i a de corrosidn en l a p a r t e e x t e r i o r d e l d i s c o de -a c e r o inoxidable. E s t e problema s e ha m i n i m i zado cubriendo con p l d s t i c o l a descarga p a r a e v i t a r l a contaminacidn ambiental. Para r e g u l a r l a p r e s i d n en e l s i s t e m a de t r a n s p o r t e de vapor, s e t i e n e n derivaciones a si-l e n c i a d o r e s , con v6lvulas de c o n t r o l operadascon actuadores e l g c t r i c o s desde e l c u a r t o de c o n t r o l de l a Central. A e s t o s conjuntos s e l e s denomina "sistemas de r e g u l a c i d n " , y s e -u t i l i z a n cuando se t i e n e b a j a demanda de energ l a e l g c t r i c a en e l s i s t e m a , cuando s e present a n rechazos de carqa o en periodos de manteni miento mayor. E l t r a n s p o r t e de vapor de media p r e s i 6 n

(3.54kq/cm2 m) y e l de b a j a presi6n ( 1 . 5 kq/cm2 m ) p a r a l a unidad N o . 5 s e hace desde l a P l a n t a de Evaporacidn l o c a l i z a d a j u n t o a l a laguna. La l o n q i t u d de las t u b e r i a s e s de 1550 m. y -10s dizmetros son 40 pulqadas l a de media y 38 pulgadas l a de b a j a , respectivamente. CONDUCCION DE AGUA SEPARADA

LOS c r i t e r i o s p g ra e l manejo d e l agua separada en e l Campo Gez t6rmico de Cerro P r i e t o han t e n i d o d i f e r e n t e s e t a p a s ; oriqinalmente s e enviaba a l a laguna de evaporacidn mediante t u b e r i a s s i n a i s l a m i e n t o tGrmico, manteniendolas p r e s u r i z a d a s con -o r i f i c i o s colocados pr6ximos a l a descarqa par a r e d u c i r l a formacidn de vapor d e n t r o de l a t u b e r i a y p o r l o t a n t o e l qrado de s o b r e s a t u r c cidn de l a s i l i c e , l a velocidad de i n c r u s t a - ci6n y l a c a i d a d e p r e s i 6 n , r e s u l t a d o una ma-yor capacidad de conducci6n. Algunas t u b e r i a s s e mantuvieron operando e n e s t a s condiciones d u r a n t e mds de 6 afios.

Cuando se i n i c i 6 l a construccidn de l a P l a n t a de Evaporacidn p a r a aprovechar e l aqua que see s t a b a desechando a l a laguna, hubo necesidadde modificar l a t r a y e c t o r i a , l a l o n g i t u d y e l di6metro d e l a s t u b e r l a s de conducci6n e x i s t e n t e s , quedando e l a r r e q l o a c t u a l mostrado en l a Figura No. 7 , y de c o l o c a r a i s l a m i e n t o tgrmico p a r a e v i t a r pgrdidas de c a l o r que originalment e no e r a n e c e s a r i o . A l a l l e q a d a a 10s co--l e c t o r e s de l a P l a n t a de Evaporacidn s e s i g u i e ron u t i l i z a n d o 10s o r i f i c i o s de regulaci6n con 10s mismos f i n e s o r i g i n a l e s , con l a modalidadde que se colocaron en cada o r i f i c i o d e r i v a c i o nes de 6 pulgadas de didmetro p a r a e l a j u s t e f i n o , ya que e l c r i t e r i o de dimensionamtento-d e 10s o r i f i c i o s f u e e l que manejaran e l 50% d e l f l u j o y e l r e s t o s e r e q u l a r i a mediante l a vdlvula colocada en l a d e r i v a c i 6 n mencionada. Cuando l a P l a n t a de Evaporaci6n o alguno de -10s n6dulos no e s t 6 operando, se puede d e r i v a r e l aqua de 10s c o l e c t o r e s a l a laguna (Fiqura-

No, 3 6).., En l a Tabla N o . 2 s e m u e s t r a l a canti'dad de aqua separada prodiicida en cada pozo y en l a Tabla No. 4 las c a r a c t e r f s t i c a s quimicas.

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E l p r i n c i p a l problema en e l t r a n s p o r t e de agua separada en Cerro P r i e t o I e s ocasionado por -

l a depositacidn de s f l i c e en las paredes de -l a s t u b e r i a s . Gradualmente, e s t a i n c r u s t a c i 6 n provoca mayores c a i d a s de p r e s l 6 n llegando a i n u t i l i z a r en algunos casos l a t u b e r f a , hacien do n e c e s a r i a su limpieza, 0 su reemplazo. Se ha determinado experimentalmente que l a s v e l o c i d a d e s de i n c r u s t a c i d n en l a s t u b e r i a s d e aqua y en 10s equipos por 10s que se conduce aqua o mezcla en Cerro P r i e t o , dependen de dos f a c t o r e s principalmente; e l qrado de sobresat: i r a c i d n de l a s i l i c e con r e s p e c t o a l a s o l u b i ldad de l a s i l i c e amorfa y e l vaLor d e l pH. Otros f a c t o r e s que i n f l u y e n en menor grado enl a velocidad de i n c r u s t a c i d n son: l a temperat u r a , l a s a l i n i d a d , 10s e f e c t o s hidrodingmicos, l a cantidad de s d l i d o s suspendidos y e l contenido d e gases. Por o t r o l a d o , t a n t o e l gradode s o b r e s a t u r a c i 6 n de l a s f l i c e como e l p H , d e penden de las c a r a c t e r f s t i c a s d e l yacimiento y de las formaciones de l a s que proviene e l f l u i do en cada pozo. La Tabla N o . 1 1 y l a Figura N o . 8 , muestran -l a s velocidades de i n c r u s t a c i 6 n mds e l e v a d a s , a medidas en t u b e r i a s de agua separada s i n a i s l miento tGrmico, aquas a r r i b a d e l o r i f i c i o de regulacidn. 9 s e m u e s t r a l a seccidn t r a n s v e r s a 1 y l o n g i t u d i n a l de l a t u b e r i a de agua SE parada de 10 pulgadas de d i h e t r o y de c a s 1 2000 m. de l o n q i t u d , que estuvo conduciendo aqua desde e l pozo M-91 h a s t a l a laguna de eva poracidn. L a causa que o r i g i n 6 e s t a i n c r u s t a cidn t a n s e v e r a f u e que l a t u b e r i a se estuvo operando con un d i h e t r o de o r i f i c i o demasiado grande en e l lado de l a d e s c a r g a , provocando a l t a evaporacidn d e l aqua d e n t r o de l a t u b e r l a , elevada s o b r e s a t u r a c i 6 n d e s i l i c e y por lo ta"_ t o rspida incrustacibn. En l a Fiqura N o .

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Para t r a t a r de r e s o l v e r e l problema de l a s i n c r u s t a c i o n e s en t u b e r f a s p a r a aqua separada, l a CFE c o n t r a t d 10s s e r v i c i o s d e l I n s t i t u t o d e Investiqaciones E l g c t r i c a s , para i n v e s t i g a r 10s mctodos de prevenci6n d e i n c r u s t a c i o n e s ymgtodos de limpieza de t u b e r i a s i n c r u s t a d a s , habigndose concluido que p a r a salmueras d e a l t o contenido d e s f l i c e r e s u l t a r i a mbs econ6mico e v i t a r l a formacidn de i n c r u s t a c i o n e s dismL nuyendo e l v a l o r d e l pH mediante a d i c i d n d e zcido a1 aqua, con l o c u a l s e puede disminuirh a s t a 10 veces l a velocidad de i n c i d e n c i a de l a incrustacidn. S i n embargo, p a r a a p l i c a r e 2 t e mctodo de prevenci6n s e r e q u i e r e r e s o l v e r e l problema de c o r r o s i d n que se o c a s i o n a r i a a 1 utilizarlo. En e l cas0 de salmueras con bajocontenido de s i l i c e , s e concluyd que e s mds

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econ6mico p e r m i t i r que l a incrustacidn s e I l e ve a cab0 y a l tdrmino de 10s 8 6 10 aiios ques e estima p o d r h n continuar operando l a s tuber i a s de aqua que estuviesen e n e s t e caso, proceder a s u limpieza o reemplazo. De 10s d i f e r e n t e s procedimientos de limpieza que s e proba ron s e recomend6 l a limpieza con chorro de - agua a elevada p r e s i 6 n , o e l m6todo de c a v i t a ci6n. Otro m6todo de limpieza recomendado fue e l u s 0 de tapones raspadores “ p i g s “ . De e s t o s mdtodos ninguno ha s i d o l o suficientemente des a r r o l l a d o , y requieren ser econdmicamente demostrados s u s resultados. Hasta l a fecha s o l o s e ha u t i l i z a d o por CFE en e s c a l a mayor, l a -limpieza m e c h i c a , para l o que se ha requerido c o r t a r en secciones c o r t a s l a t u b e r i a , colocar l a en posici6n v e r t i c a l y golpearla para des-prender l a i n c r u s t a c i 6 n . Una vez hecho & t o , s e procede de nuem a i n s t a l a r l a . En l a Fiqura No.

10 s e muestra l a evoluclbn de 10s soportes para t u b e r i a s de agua separada. Originalmente se u t i l i z a r o n r o d i l l o s para perm i t i r e l deslizamiento de l a t u b e r i a (Fiqura No. l o a ) , per0 debido a 10s problemas que presentaron, s e dejaron de u t i l i z a r . Las Figuras Nos. 10b y 1Oc indican 10s t i p o s de soportes que substituyeron a 10s o r i g i n a l e s . Durante l a construcci6n de l a P l a n t a de Evaporaci6n s e u t i l i z a r o n soportes hechos de t u b e r f a de 4 pulgadas de perf11 t i p 0 canal e n l a p a r t e i n f e - r i o r de l a s t u b e r i a s para e v i t a r e l desgaste de Qstos por e l movimiento.

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En Cerro P r i e t o I s e -t i e n e experiencia en l a conducci6n de mezcla a La dis-d i f e r e n t e s d i s t a n c i a s y condiciones. t a n c i a ma’s l a r q a a l a que se ha transportado mezcla e s de 1800 m. desde e l pozo M-53 a 1 M-39.

L a s p r i n c i p a l e s v e n t a j a s de conducir mezcla e n

l u p r de acpa y yapor por separado son l a s sigui’entes: a). Se r e q u i e r e menor cantrdad de t u b e r l a s . b ) Las i n s t a l a c i o n e s en e l pozo son mbs sencillas. c ) Menor contaminacibn ambiental, a 1 r e q u e r i r s e de menor s u p e r f i c i e . d ) E s menor e l costo de operaci6n y mantenimien t o de m6dulos de separaci6n-evaporaci6n, a l concentrarlos en un s o l o s i t i o y con posibil i d a d e s de instrumentarlos y equiparlos consistemas de c o n t r o l remoto. Una de l a s p r i n c i p a l e s desventajas que t i e n e e l t r a n s p o r t e de mezcla es que s e p i e r d e l a d i s p o n i b i l i d a d d e l pozo durante e l perlodo en que l a t u b e r i a de mezcla requiera limpieza o reposici6n.

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CONDUCCION DE GASES AI i n i c i a r su operacibnl a Central de C P - I , 10s gases incondensables se descargaron e n e l mismo s i t i o por chimeneas, a 40 m. de a l t u r a . S i n embargo, en ocasionesl a s condiciones atmosfdricas son t a l e s , que l a concentraci6n de H 2 S e n e l s i t i o s e incrementa mucho y aunque no ha lleqado a l i m i t e s p e l i g r o s o s , s e consider6 conveniente a l e j a r l a d e s c a r ga a un punto prbximo a l a laguna de evapora-r ci6n. Para e s t o s e disefio e i n s t a l 6 una tuber i a de r e s i n a epoxica reforzada con f i b r a de v i d r i o de 26 pulgadas de didmetro y 1400 m. de i lonqitud, cuya t r a y e c t o r i a se muestra e n l a Fgura No. 1 2 .

CONDUCCION DE MEZCLA

En l a Fiqura N o . 1 1 s e muestran l a s trayecto-r i a s y didmetros de l a s t u b e r i a s de mezcla que s e han empleado. La conducci6n de 180 ton/h de mezcla d e l pozo M-42 a 1 M-38, con r e c o r r i d o d e 457 m y t u b e r i a d e 1 2 pulgadas de digmetro, continfia operando s i n problemas desde hace 9 -

aiios. A 1 i q u a l que en e l cas0 d e l t r a n s p o r t e de aqua

separada, e l p r i n c i p a l problema en e l t r a n s p o r t e de mezcla es la presencia de incrustaciones.

La Tabla No. 1 2 muestra las condiciones promed i o anuales en l a s que oper6 l a t u b e r i a de me? c l a d e l pozo M-53 a 1 M-39. Como s e puede ob-s e r v a r en l a t a b l a , l a causa que o r i g i n 6 l a -suspensi6n de l a conduccidn de mezcla en e s t e caso, fue l a i n c r u s t a c i 6 n en e l pozo. La i n s pecci6n que s e hizo de l a t u b e r i a de mezcla, demostr6 que no estaba demasiado incrustada. Se c o r t 6 a 1300 m. d e l pozo M-53 encontrando un t i p o de incrustacidn muy d i f e r e n t e a 1 que s e presenta en l a s t u b e r f a s de conducci6n de aqua, de aspect0 v i t r e o , muy dura, con espesor de 1.25 cm. en la p a r t e s u p e r i o r y de 2.5 a -3.7 c m . en l a p a r t e i n f e r i o r de l a misma.

A 1 p r i n c i p i o de s u operacibn, para e l manejo de e s t o s gases s e u t i l i z a r o n v e n t i l a d o r e s i n s t a l a d o s en l a propia C e n t r a l , 10s c u a l e s a 1 p o co tiempo dejaron de operar por l a excesiva co r r o s i 6 n de sus componentes. La combinacidn d e H2S y oxfqeno hacen que e s t a mezcla tenga ca-r d c t e r s6mamente aqresivo. LQS v e n t i l a d o r e s s e dejaron de u t i l i z a r , observdndose que l a -presidn de descarga de l a filtima etapa d e l sis tema de extracci6n de gases, e r a s u f i c i e n t e pd ra descarqarlos a t r a v 6 s de la tuberia a n t e s d e s c r i t a . La cantidad de gases que se envfana l a laguna e s de 25 ton/h. En l a Tabla N O . 13 se muestra e l a n a l i s i s de gases incondensables, a que s e hace r e f e r e n c i a .

=

SEPARADORES, SILENCIADORES Y EQUIPOS DIVERSOS En l a Fiqura No. 1 3 , se muestran 10s principal e s equipos que s e han u t i l i z a d o e n Cerro P r i e t o I y en l a s Figuras NOS. 1 4 y 15 1 0 s a r r e - - r 910s de equipos en plataforma, fn e s t o s dos 61

timos casos, a n t e s y despuds de la 5a. unidad: D e e l l o s , por su importancia y nfimero, resal--

t a n 10s separadores t i p o Webre, de 54 pulgadas de didmetro, cuyo disefio o r i g i n a l fue s i m i l a r a 1 empleado en Wairakei, N . Z . , per0 que en Cer r o P r i e t o ha s u f r i d o algunos cambios para a-d a p t a r l o a l a s condiciones de e s t e campo. Los cambios mds notables son l a a l t u r a d e l tubo -concdntrico, l a posici6n de l a descarga de --aqua y e l cambio de l a secci6n rectangular a c i r c u l a r a l a entrada d e l separador. La a l t u -

ra de l a t u b e r f a i n t e r i o r conc6ntrica s e aumen t 6 p a r a incrementar l a c a l i d a d d e l vapor s e p a r rad0 y l a s a l i d a de agua e n l a p a r t e i n f e r i o r , p a r a mejorar e l c o n t r o l de n i v e l d e n t r o d e l s e parador y e v i t a r i n c r u s t a c i o n e s en l a cbmara 1 de aqua que producfa inundaciones y a r r a s t r e de agua en e l vapor. L a v e n t a j a de 10s cambios s e r e f l e j a r o n muy pronto en l a mayor c a l i d a d d e l vapor separado y en l a menos f r e c u e n t e necesidad d e l i m p i a r l a s t u r b i n a s , cuyos d l a b e s y diafragmas se o b s t r u i a n con s i l i c e d i s u e l t a en e l aqua a r r as t r a d a aumentando e l i n d i c e d e d i s p o n i b i l i d a d en l a s t u r b i n a s .

En l a Tabla NO. 1 4 s e muestran 10s v a l o r e s dec a l i d a d de vapor en 10s pozos de cP-I. Recientemente, a 1 d e s c u b r i r un yacimiento de mayor p o t e n c i a a mayor profundidad, en l a m i s m a zona e n l a que s e perforaron 10s primeros pozos p a r a CP-I, e l tamaiio de 10s separadoresde 54 pulgadas ha r e s u l t a d o i n s u f i c i e n t e , ya que e s t d l i m i t a d o a l a separacidn e f i c i e n t e de 250 ton/h. de mezcla. Lo a n t e r i o r o b l i q 6 a -c o n s t r u i r separadores con mayor didmetro ( 7 8 pulgadas) p a r a poder u t i l i z a r mayor capacidadde produccidn de 10s pozos profundos. Uno de 10s p r i n c i p a l e s problemas que s e t i e n e con l a operacidn d e 10s separadores e s que a l v a r i a r l a p r e s i 6 n en e l sistema de t u b e r z a s de vapor, o r i g i n a d a a 1 abrir o c e r r a r l a s vdlvu-las d e l sistema de r e g u l a c i h , 10s n i v e l e s deagua en 10s separadores v a r i a n considerablemen t e , llegando en ocasiones a inundarse con e l consecuente a r r a s t r e de agua. Por 6 s t a razcn, s e ha optado por o p e r a r 10s separadores con -muy b a j o n i v e l 6 ninguno, originando l a p6rdida de vapor en l a descarga de agua. De l o ant e r i o r se deduce l a conveniencia de diseiiar un sistema de requlaci6n que permita mantener c o n s t a n t e l a p r e s i 6 n en 10s ramales de vapor.

-

Se t i e n e n operando en Cerro P r i e t o 4,l separado res, d e 10s c u a l e s 32 son p a r a produccidn de 1 vapor p r i m a r i o , 3 p a r a vapor de media y 6 p a r a vapor de b a j a . Otra de l a s p a r t e s importantes de l a s i n s t a l a c i o n e s en l a plataforma de 10s pozos son 10s s i l e n c i a d o r e s . Originalmente s e u t i l i z a r o n -con e l mismo p r i n c i p i o que ~ O Sde Wairakei, N. 2.; s i n embargo, l a capacidad de 6 s t o s r e s u l t 6 i n s u f i c i e n t e y s e diseiiaron 10s t i p o s mostra-dos en l a s Fiquras Nos. 139 y 13h, con capacidad p a r a manejar 300 y 500 ton/h. de mezcla -respectivamente. E l p r i n c i p a l problema que se ha t e n i d o en los-

s i l e n c i a d o r e s e s l a eliminaci6n de l a s i n c r u s t a c i o n e s , l a c u a l se efectGa mecbnicamente 6 con chorros de agua a elevada velocidad. Nuevos m6todos de limpieza s e e s t & estudiando. Se t i e n e n operando e n C P - I , 58 s i l e n c i a d o r e s de concreto de 10s t i p o s mostrados en l a s Figu

r a s Nos. 139 y 13h.

Para l l e y a r a e s t o s d i s e -

nos, f116 n e c e s a r i o probar v a r i o s t i p o s de mate r i a l e s p a r a l a s chimeneas, incluyendo a c e r o a i carbbn, madera y fi’nalmente, 10s de r e s i n a pol i e s t e r , reforzados con f i b r a de v i d r i o . Para evaluaci6n de nuevos pozos, frecuentemente seu t i l i z a n s i l e n c i a d o r e s metdlicos p o r t s t i l e s . En e l campo de C P - I , e r a f r e c u e n t e que 10s pozos a r r a s t r a r a n arena de l a formacidn p r o d u c t o

r a , l a c u a l debe d e t e c t a r s e a tiempo para e v i t a r que s e a a r r a s t r a d a e s t a arena e n e l vapor. Para d e t e c t a r l a p r e s e n c i a de a r e n a , s e u t i l i zan 10s muestreadores que aparecen en l a s F i g 5 r a s Nos. 1 4 y 15. Como se puede observar en d i c h a s f i g u r a s , no s e emplean j u n t a s de expans i 6 n e n t r e e l pozo y e l separador. Original-mente s e u t i l i z a r o n , per0 debido a 10s problem a s p a r a s u mantenimiento se abandon6 su uso,habigndose adpotado l a p r 6 c t i c a de i n s t a l a r l a curva de entrada a 1 Separador en l a s condiciones f i n a l e s de operacidn d e l pozo. Cuando no s e r e q u i e r e 6 no s e puede conducir e l agua separada por tuberias, s e descarga a c a n a l e s a b i e r t o s , conduciendola h a s t a un punto prdximo a l a laguna de evaporacitjn, en donde s e bombea a 6 s t a . Frecuentemente s e r e q u i e r e d r a g a r e s t o s c a n a l e s , en donde se depositan -grandes volGmenes de s l l i c e . CONCLUSIONES En Cerro P r i e t o I se han genera do 10 m i l l o n e s de MWh y se han producido 300 1 millones de toneladas de f l u i d o geot6rmico. La l o n g i t u d de l a red a c t u a l de t u b e r i a s de v a por con didmetro de 1 2 a 40 pulgadas, e s de -24,240 m. L a red de t u b e r l a s de aqua con dibEsmetros de 8 a 16 pulgadas es de 46,500 m. tdn en operacidn 32 pozos, 41 separadores, 58s i l e n c i a d o r e s , 7 secadores de vapor y 290 v.51v u l a s de 8 a 30 pulgadas de dibmetro. La co-rrosi6n e n l a s t u b e r i a s y equipos s u p e r f i c i a - l e s no ha s i d o un problema grave. E l p r i n c i - p a l problema de mantenimiento ha s i d o l a l i m - p i e z a de l a s i n c r u s t a c i o n e s y sedimentos de si l i c e en t u b e r i a s , equipos y canales. Frecuen: t e mantenimiento e s n e c e s a r i o para conservar l a capacidad de l a s t u b e r f a s de aqua, de 10s separadores y de 10s c a n a l e s . Las tuberias de 10s pozos y en algunos casos e l yacimiento m i s mo, tambien han s i d o a f e c t a d o s por l a s i n c r u s r taCiOneS. A b l a s pequeiias cantidades de s i l i c e que se a r r a s t r a n en e l vapor separado o r i g ? nan d e p 6 s i t o s en l a s t u r b i n a s disminuyendo s u z capacidad.

-

-

Dada l a gran e x p e r i e n c i a o b t e n i d a durante 1 2 aiios e n Cerro P r i e t o I , p a r a e l t r a n s p o r t e def l u i d o s geot&micos, s e recomienda aprovecharl a p a r a que s e tome en cuenta a1 d e s a r r o l l a r l a i n g e n i e r i a conceptual de f u t u r o s proyectosqeot6nnicos en campos de l i q u i d 0 dominante.

-

Tabla 1 .

Valores anuales de generaci6n e l 6 c t r i c a y e x t r a c c i 6 n de energid, de 1973 a 1984 en e l Campo Geotirmico de Cerro P r i e t o I . ~~

Generaci6n elgctrica

Aiio

Gwh

Producci6n de mezcla ton

x 10

Energia ex t r a i d a Kcal x 10

12

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984

193 463 518 579 592 598 1019 91 5 964 1267 1221 1264

10.2 18.7 19.1 22.1 23.8 22.0 38.2 33.1 33.0 38.7 39.5 36.2

3.3 6.0 6.1 7.1 7.6 7.1 12.3 10.6 10.6 12.4 12.7 11.6

11.9 12.1 11.6 11 .o 9.8 10.4 9.2

Total:

9593

334.6

107.4

11.2

Tabla 2 .

~

Consumo e s p e c i f i c o de c a l o r 3 K c a l / K w h x 10

17.1 13.0 11.8 12.3 12.8

Pozos i n t e g r a d o s a l a P l a n t a de Cerro P r i e t o I .

(Marzo 1985) ~~

P r e s i 6 n de separaci6n

(m)

P r e s i 6 n en l a cabeza 2 [kg/cm ) m

1782 1946 1766 2567 21 19 1801 1212 1293 1263 1377 1295

12.30 28.40 42.18 I O . 54 45.69 56.90 9.00 28.41 7.38 31.64 10.54

6.00 6.67 7.17 7.03 8.43 7.31 6.39 6.32 7.38 8.15 6.67

28.4 34.9 59.4 34.3 88.7 54.9 17.6 32.0 57.5 35.0 13.2

25.9 46.5 51.4 80.5 134.1 58.7 47.6 101.6 144.9 113.4 25.4

1772 1591 1818 1331 1555 1709 1261 1197 1306 1222 1414

1381

20.04

7 -94

40.5

104.0

1302

1266 1295 1286 1311 1246 1390 1727 1250 1567 1883 181 1 1691 1379 2294 1990 2008 1725 1692 1627 2096

9.84 6.32 7.87 11.9 6.46 6.67 58.34 10.54 16.50 23.90 15.46 8.22 6.88 10.40 7.03 16.87 18.55 6.33 7.03 23.55

7.10 6.32 6.18 6.11 6.46 6.04 6.88 7.17 6.95 6.67 6.74 7.38 6.60 7.03 6.81 6.81 8.15 6.04 6.82 7.63

24.0 20.9 39.7 40.4 18.7 13.1 34.6 58.4 70.9 53.6 47.1 70.1 28.5 43.7 27.9 27.1 75.1 19.8 34.8 56.9

68.6 83.0 109.0 130.8 55.4 22.0 70.1 169.7 138.2 98.2 100.1 25.4 84.8 83.8 3.9 14.1 18.8 65.6 8 2 .O 45.6

1251 1116 1250 1186 1226 1469 1392 1245 1412 1436 1369 2226 1225 1421 2506 2065 2365 1174 1325 1664

Profundidad. PO20

E- 1 E- 2

E-4 E-6 E- 7 M- 1OA M-I 1

M-14 M- 19A M- 20 M-21A M- 25

M-26 M- 29 M-35 M-42 M-43 M-45 M-47 M- 50 M-51 M-73 M- 79 M-84 M-90 M-91 M-102 M-103 M- 104 M-114 M-120 M-130

(kg/cm2)m

F l u j o de vapor (ton/h)

Flujode aqua (ton/h)

Entalpia de mezcla (KJ/Kg)

Tabla 3.

CP I

CP I1

Profundidad promedio de pozos ( m ) .

1635

2500

2200

E n t a l p i a promedio de l a mezcla producida (KJ/Kg)

1423

1510

1632

Temperaturd promediodel Yacimiento ("C)

300

328

34 5

So'lidos t o t a l e s d i s u e l t o s en e l agua separada a p r e s i 6 n atmosfErica (mg/l)

25000

33000

32500

Gases incondensables e n vapor separado ( % e n peso)

1.4

0.8-1.2

0.8-1.2

Tabla 4.

Po20 E- 4 E- 6 E- 7 M-1OA M-14 M-21A M-35 M-51 M-84 M-90 M-9 1 M-103 M-105 M-114 M- 120

*

C a r a c t e r i s t i c a s promedio de pozos. CP I11

Composici6n quimica d e l agua separada de pozos de Cerro P r i e t o I

P r e s i 6 n e n P r e s i 6 n de l a cabeza separaci6n 2 2 Kg/m ) m (Kg/cm )m

56.2 12.0 68.8 64.5 30.6 7.7 8.8 16.9 8.8 7.7 9.8 8.8 9.1 7.6 17.9

8.5 8.4 9.5 9.0 7.3 7.5 7.7 8.1 8.4 7.6 7.8 8.1 8.6 7.5 9.5

(Marzo 1 9 8 4 ) .

Concentraciones (mg/l) * pH

6.6 7.2 7.0 6.2 6.8 7.2 8.1 7.1 7.0 7.6 7.1 6.9 7.3 7.8 6.7

Na

10972 10909 12319 9856 4679 5761 4227 61 00 10485 4562 10021 6104 9742 71 10 10151

K

Li

Ca

3066 2959 3449 2912 804 1263 782 1477 2958 926 2704 1405 2279 1357 2946

29 29 33 31 12 16 10 16 29 12 27 15 25 17

414 509 489 373 241 256 158 201 470 158 373 191 531 432 382

30

C1

20299 20316 23274 18587 8335 10232 7503 10795 19797 7886 18547 10795 17798 13281 18815

HCO?

STD

Si02

49 80 47 76 127 117 71 100 63 76 71 92 49 72 51

36435 37138 41624 33300 14779 18414 13413 19039 35463 14309 34003 19445 3 209 5 23270 33762

1002 1094 1266 1183 69 3 838 706 927 925 708 1308 1069 9 38 718 1112

L a s muestras fueron tomadas a l a p r e s i 6 n de separaci6n y 10s d a t o s reportados a condiciones a t m o s f 6 r i c a s .

Tabla 5.

Composici6n quimica (mg/l) y propiedades f i s i c a s d e l agua separada a l a p r e s i 6 n atmosf6rica de 10s pozos M-14, M-30, M-91 y M-53 de Cerro P r i e t o (noviembrede 1980).

Especie

sim.010

M- 1 4

M-30

M-91

M-53

Cloruros

c1-

11,242 6,090 1,060 81 3 342 28.9 33.5 1.3 17.5 14.5 17.2 5.2 4.5 11.0 2.4 0 -43 1.7 1.5 0.59 1.5 0.07 0.12 0.10 0.04 0.16 0.15 0.03 1.4 21,800 20,000 I .008 8.5

14,200 7,350 1,520 975 528 22.2 11.3 1.7 33.5 18.7 17.4 5.6 7.4 13.0 1.3 2.5 2.4 0.47 0.58 0.66 0.06 0.15 0.15 0.03 0.13 0.20 0.03 1.8 26,522 23,000 1.011 8.3

19,130 9,950 2,585 1,241 432 12.7 14.1 2.6

18,105 9,240 2,790 1,301 406 16.2 8.23 2.4

23.5 16.5 4.1 14.0

25.1 25.3 2.5 10.4

1.4 3.0

5.5 2.8

1.4 0.07 0.62 0.10 0.03 0.07 0.24 0.07 1.3 36,867

1.6 0.08 0.39 0.20 0.06 0.06 0.26 0.06 1.3 34,902

1.019 8.4

1.016 8.4

Na Sodio K Potasio Si02 Silice Ca Calcio COT C arbona t o s HCOf Bicarbonatos cs Cesio BrBromuros Li Litio B Boro Sr Estroncio Rb Rubidio SOT Sulfatos FFluoruros Mn Manganeso Fe Fierro As Arsgnico I Iodo Magnesio Mg cu Cobre Cr Cromo A1 Aluminio Zn Zinc Plata Ag Pd Paladio Cd Cadmio s= Sulfuros S 6 l i d o s D i s u e l t o s STD Conductividad pmhos Densidad g/ml Acidez PH

Tabla 6 .

POZO

-

-

-

-

-

-

-

-

Composici6n quimica d e l vapor separado e n pozos d e Cerro P r i e t o I

PresiBn PresiBn en l a de sepg cabeza raci6n. (Kg/cm2)m (Kg/cmZ)rn

H20

Componentes ( % en peso) NH3 H2 N2 CH4

C02

(Mayo 1 9 8 2 ) . Ar

He

10-2

M-21A

19.0

6.4

98.13

1.75

8.1

1.8

10.3

3.3

3.7

1.3

0.0

M-3 1

7.0

6.5

98.62

1.29

6.3

1.8

8.0

3.2

4.7

1.2

1.7

M-51

9.0

7.7

98.37

1.52

6.9

2.2

7.6

4.1

7.0

1.8

4.2

M-104

8.1

7.1

96.61

3.19

13.6

4.6

8.0

11.6

6.4

1.5

0.0

M-105

9.2

8.2

99.17

0.77

3.9

1.5

4.1

2.8

5.8

1.5

3.4

M-120

36.9

8.8

98.20

1.68

8.1

1.9

12.4

4.1

4.3

1.1

6.0

E- 3

31.5

6.7

98.20

1.66

7.9

1.3

14.2

4.0

4.8

1.2

4.3

Tabla 7 .

Relaci6n de pozos i n t e g r a d o s a 10s ramales de vapor de (Marzo 1 9 8 5 ) . Cerro P r i e t o I

Ramal

POZOS

(No.)

Cantidad

1

5

F l u j o de Vapor

conectados por ramal Identificaci6n M - ~ O A , M-11, M-42,

(Ton/H)

M-114,

167.5

M-130

5

2

p4-14,

M-19At

M-25,

M-29

r

169.6

M-43 3

2

M-20 y M-26

4

4

E-1,

M-21At

5

4

E-4,

M-41,

6

3

M-51,

7

5

E-2, M-102, M-120

8

4

E-6,

Tabla 8.

M-50,

M-84,

E-?,

59.0 M-35,

M-45

94.4

M-90

199.4

M-91

184.7

M-103,

M-73,

M-104,

M-79

221.9 223.7

D i h e t r o s y l o n g i t u d e s de t u b e r i a s de vapor y agua en C . P . I .

~

Dihetro

Longitud I n s t a l a d a (m) ~~~

(Pulgadas)

Tuberia de vapor

8

~

Tuberia de agua

19300

10

-

12

1160

6680

16

41 00

2620

18

4400

-

20

1900

24

1050

26

1550

30

1920

32

3170

34

1890

38

1550

40

1550

To t a l :

24240

17900

46500

Tabla 9 .

No.

Espesores de pared de t u b e r i a , medidos en 10s ramales d e Cerro P r i e t o I .

Ramal Dihetro (pulqadas)

Espesores Cgdula

Domo Superior

xs xs xs xs

34 34 34 34 30 32 32 32

STD

STD

Pozo

1 2 3 4 5 6 7 8

M-11 M-43 M-26 M-45 M-90 M-91 M-I 04 E-6

Tabla 11.

Presio'n en el Separador (Kg/cmz)m

Costado Izquierdo -

-388

6.1 6.1 6.1 6.1 6.2 6.2 6.3 6.2

D i s tancia Pozo-Colector

(m) 1430 1945 1165 1815 2955 231 5 2525 2435

Incrustacio'n observada e n t u b e r i a s de aqua separada (Mayo 1979) en Cerro P r i e t o I .

2

1100 1000 900 900 800 a50 700

Tiempo de operaci6n (afios)

4.2 6.2 6.2 4.7 5.3 5.3 2.7

Espesor de incrustaciones

Velocidad de incrustaci6n

(mm)

(mm/afio)

19.1 19.1 12.7 6.4 6.4 4.8 1.6

~~

-546 .532 .543 .546 -433 -417 -425 -377

.553 .540 .525 -539 .424 -41 1 -406

P r e s i 6 n d e l Colector en P l a n t a (Kq/cm2)m

6.9 6.3 6.6 6.7 6.7 7.5 8.6 8.8

Si o

M- 1 9A M- 5 M-11 M-21A M- 8 M-26 M-14

costado Derecho

Presio'n en 10s separadores de 10s p z o mas l e j a n o s de C.P.

Ramal

Po20

.544 .525 .526 .534 .413 -402 .411 .378

.565 .544 -530 .543 .413 .4 34 .404 .378

STD STD

Tabla 10.

Domo I n f e r i o r

(pulqadas)

4.5 3.1 2.1 1.4 I .2 0.9 0.6

I.

~~

~-

Tabla 1 2 .

Condiciones promedio anuales d e operaci6n de l a t u b e r i a de mezcla d e l pozo M-53 a 1 M-39. Presi6n en sep5 rador pozo M-39

Aiio

P r e s i 6 n en l a cabeza 2 (kg/cm )m

(kg/cm2) m

ton/h

kca 1/ kg

1978

11.0

6.7

114.0

367

1979

10.0

6.5

86.0

359

1980

9.1

6.5

70.0

3 50

1981

8.6

6.8

51 -0

330

1982

7.9

7.0

32.0

31 5

Tabla 14.

POZO

Producci6n mezcla

Entalpia

Tabla 13.

Antilisis de gases incondensables

Compuest o

%

5.29 58.44 2.32 0.03122 7.7895 26.0086 0.1086 0.0014 0.0003679 0.000415 0.0003462

H20 co 2 H2s

H2 02 N2

CH4 Etano Propano I sobutano n-bu tan0

Calidad d e l vapor separado en pozos de Cerro P r i e t o I (Enero 1985) P r e s i 6 n (kg/cm2)m Cabeza Separador

Produccio'n de vapor ton/h

Calidad de vapor

(%I ~

E- 1 E- 2. E-6

E-7 M- 1OA

M-11 M-14 M- 19A M- 20 M-21A M-25 M- 26 M-35 M-42 M-43 M-45 M-47 M-51 M-73 M- 79 M- 50 M-91 M-102 M- 103 M-104 M-105 M-114 M- 1 20 M- 130 M-169

3 20 334 150 650 820 110 414 100 460 190 280 140 120 175 86 100 830 21 6 305 228 103 145 99 21 2 260 325 91 230 91 870

106.5 103 111 145 121 96 98 95 92 108 120 104 105 102 73 98 110 111 115 114 100 109 97 105 127 115 90 1 24 89 110

61.5 30.1 34.1 91 .o 57.4 18.3 31.1 57.6 34.5 11.9 41.1 23.7 39.8 39.1 18.8 14.2 42.6 67.4 51.7 47.5 31.3 53.9 27.0 25.8 76.6 29.1 21.5 46.9 37.9 33.2

en peso

99.998 99.995 99.998 99.992 99.986 99.997 99.997 99.998 99.993 99.998 99.997 99.998 100 .ooo 100.000 100.000 99.998 99.999 99.990 99 * 999 99 - 9 9 4 99.992 99.991 99.983 99.993 99.996 99.993 100.000 99.996 100.000 99.992

ESCALA

e:z/J

Figura 1.

Localizaci6n de pozos en el Campo Geot6rmico de C.P. 1.

110,

7

2

-co

\

pazo M-l

1

IW

loo

fp

60

f

60

Fig. 2.

Curvas caracteristicas de producci6n para 2 pozos de C.P. 1.

AGUA SEPARADA

h

MEDIA PRESION

Srdimrntos VAPOR DE AL7A PRESION

Consolldadoa BAJA PRESION

Baaamanto

A

Figura 3 .

CONDENSADORES

Diagrama de f l u j o de Cerro P r i e t o I .

M-747

~

Figura 4.

Arreglo de l a s t u b e r i a s de vapor de Cerro P r i e t o I .

SILLETA

QUlAS

a).- SOPORTE LIERE (1973)

b).- SOPORTE GUIADO (1979)

d.-SOPORTE Fiqura 5.

LIBRE (1982)

Tipos de s o p o r t e s empleados para t u b e r i a s de vapor.

T U B E R I A DE V A P O R /

I

Fiqura 6 .

Sistema de drenado en t u b e r i a s de vapor.

Mq169

0

M%!7

M- 125

F i g u r a 7.

A r r e q l o d e l a s t u b e r i a s d e a q u a c a l i e n t e e n C.P.

I.

/

CERRO

PRIETO

I

I

/

/ /

/ /

/ /

/

/

,/

/

v

M-14

600

700

I

800

900

1

1000

I

1100

1200

1300

CONCMTRACION DE SLICE EN LA SALMUERA (mp/l)

F i g u r a 8.

Incidencia d e incrustaci6n observada en t u b e r i a s d e a q u a s e p a r a d a d e C.P. I . ( I n f o r m e I I E , 1981)

IpSbmmt 110'61

1

I

0

Fiqura 9.

-t

- ~-

I

mo

I

780 1000 LONOITUD DE LA TUBERIA ( ne t

Irm ro

I

IMX)

I

I

mo reooseo

)

Distribuci6n de la incrustaci6n despositada en la tuberia de aqua separada del pozo M-91. (Informe IIE, 1981)

MARC0 DE Z'B SOLO PAFtA SOIVRTES OUIAOOS\

RODILLO

7

a).-SOPORTES QUIADO PARA CAMAS DE TUBERIAS (1973)

M R C O DE

b): SOPORTES QUIADO Y LlBRE (l97e)

P'b SOLO

c).-SOPORTES QUlADO Y LIBRE I19791

Fiqura 10.

Tipos d e soportes empleados para tuberias de aqua separada.

0

T- 400 0

PLANTA e EOTER MOELECTRI C.P.I.

E-7

9

\ A 0

M-84

0

M

11-39 @Y-8 +

j.i” 12’14

Y -42

Figura 1 1 .

Y- 46 0

M -IS

0

M-SI

Tuberias de conducci6n de mezcla.

\ QQ

PLAN TA QEOTERMOELECTRIWl

0m-84

Q E-2

>

\

0

0

Y-46

0

E- I

Y-S5 0

0

Figura 12.

Y-29

Tuberia de conducci6n de gases incondensables

4

.e . ...

I

.--_._ bl SEPARADOR CON TANQUE TANQUE DE AGUA INTEGRADO DE AGUA EXTERN0 (UNIDADES 1,2,3 Y 4). (UNIDAD 5 )

a ) SEPARADOR TIP0 "WEBRE"

d ) SEPARADOR HORIZONTAL (ADAPTABLE EN L A TUBERIA)

0)

C)

SEPARADOR T I P 0 HORIZONTAL

(EXPERIMENTAL)

ELIMINADOR DE HUMEDAD 1 ) ELIMINADOR DE HUMEDAD "CENTRIFIX 'I (UNIDADES 1 , 2 , 3 Y 4)

(UNIDAD 5 )

n

g) SILENCIADOR ORIWNAL

Figura 1 3 .

h ) SILENCIADOR ACTUAL

Equipo p r i n c i p a l u t i l i z a d o en e l manejo de f l u i d o s geot6rmicos e n C.P. I.

I

Confroporo

2

Arbol de voIvuIOS

3 4

Seporodor Oico de rupfuro lndicodor de nlvel

5 6

Toma de mueltros de vopor

7

Deicorgo de vapor VOIYYIOde ol!vIo VOIVUIO e i f i r i c o IO Uoco de oriflclo I1 Volvulo d e corte 12 Ramal principal

8

9

Fiqura 1 4 .

I

Arreqla o r i g i n a l ( 1 9 7 3 ) de l a s p r i n c i p a l e s i n s t a l a c i o n e s que ponen e l equipo s u p e r f i c l a l de u n pozo geot6rmico de C . P . I .

I

4

I985

(4

COm-

I

A W A SEPARADA

1]L

AOUA SEPA RADA

b

A L A UNIDAD 5

IQ

COLECTOR

I

UI y 2

I EuiwwmR

EVAPO RADOR MEDIA PRESION

MEOIA PRESION

1 L

COLECTOR U3 y 4

I NAFQRADOR MEDIA FRESION

I

A

w R

P e

L

Figura 16.

A G U N A

D E

E V A P O R A C I O N

Diagrama d e f l u j o d e la P l a n t a de Evaporaci6n i n s t a n t s n e a .

[Source not given]

OPERATION OF SURFACE EQUIPMENT FOR RECOVERY OF GEOTHEM4L FLUIDS AT CERRO PXIETO I

Alfredo Yanon, Francisco Bermejo, Pedro Perez Federal Electricity Commission P.O. BOX 3-636 Mexicali, B.C. 21000 l ( 7 0 ) 656-3512

SUMMARY At Cerro Prieto I, 10 million MWh have been generated and 300 million tons o f geothermal fluid have been produced. The length of the present system of 12-to14-inch steam pipes is 24,000 m. pipe system is 46,500 m.

The 8- to 16-inch water

There are in operation 32 wells, 41 separators,

51 silencers, 7 steam driers, and 290 8- to 16-inch diameter valves. Corrosion in the pipes and surface equipment has not been a serious problem. The principal maintenance problem has been the cleaning of the incrustrations and sediments of silica in pipes, equipment, and channels. Frequent maintenance is necessary in order to maintain the capacity of the water pipes,

of the separators and of the channels. The pipes of the wells, and in some cases of the deposit itself, have been affected by the incrustations. Even the s m e l l amounts o f silica that are carried by the separated steam cause scales

in the turbines, d i m i n i s h i n g their capacity.

During the time since the Cerro Prieto I Plant has been in operation, the deposit has yielded more than 150,000 tons of silica dissolved in the water, of which a small amount is deposited in the pipes, equipment, and channels,

most o f it being discharged in the evaporation pond. INTRODUCTION The Cerro Preito I Geothermoelectric Power Plant has 5 units; 4 of 37.5 MW and 1 of 30 MW.

The first 2 units went into operation in 1973, the 3rd and

4th in 1979, and the 5th in 1981. A s of December 1984, the 5 units produced 9,593 GWH of electricity. This electricity was produced with 100 million tons of geothermal steam and the steam was produced with 334 million tons of mix.

One hundred seven thousand teracalories of heat were extracted. The specific consumption of geothermal heat per Kwh generated remained more or less constant. Table I shows the yearly amounts. The decrease in generation observed in 1980 and 1981 was due to problems in the cooling towers. Table 2 lists the wells that currently provide steam for Cerro Prieto I, and their principal characteristics. Fig. 1 shows the locations of the wells and of the 3 power plants. Thect'pthof vary from 1 , 2 1 2 m to 2,567 m. 2

only 6.3 kg/cm m. z

cm m.

the wells that feed steam to CP-I

The pressure at the heads varies from 58 to

The range of sepamration pressure varies from 8.4 to 6 kg/

Steam production varies from 1,116 to 2 , 5 0 0 Kj/kg.

The chief explanation

for the great differences in production, enthalpy, and pressure at the heads is depth at which each well produces. Generally,,the deeper wells work more powerful formations than the shallower ones.

Table 3 shows the most important

average characteristics of the wells of CP-I, CP-11, and CP-111. A s you can see, the depth, enthalpy, temperature, and content in dissolved solids are l e s s in~fihecase of CP-I.

The average content in non-condensable gasses in the

steam separated from CP-I is greater than the average content in CP-I1 and CP-111, which is explained by the shallower depth at which the CP-I depssit is worked, where a greater quantity of gasses accumulates. Table 4 shows the

chemical composition of 15 representative wells of CP-I, and Table 5 gives details of the chemical composition and other physical properties of the separated water bf 4 wells, the first 3 of which correspond to the CP-I zone. The silica content of the separated water at atmospheric pressure varies from 693 to 1,308 mg/l.

The highest amount of total dissolved solids (TDS)

is 41, 624 mg/l and the lowest amount is 13,413 mg/l.

Table 6 shows the chemical analysis of the separated steam of 7 wells. The high gas content of well M-104 (3.4% by weight) can be explained by the depth at which the fluid enters the well (1,275 m), which is the shallowest part of the deposit located to the east of the railroad; that is, immediately below a formation of very low vertical permeability. Fig. 2 shows the original characteristics of production (pressure at head vs. production of mix) of 2 wells of CP-I.

The difference in production

is due to the fact that the first produces from a deposit betGeen.-1,058and 1,266 m y and the second from between 1,702 and 1,946 m.

The latter formation

has a greater production potential than the former. Fig. 3 isca schematic representation o f the steam and water transport system for the Cerro Prieto I Power Plant. The 3

stages

of evaporation-separation

can be seen, by which the low, medium, and high pressure steam is obtained for the 5 units of the CP-I plant.

STEAM CONDUCTION The system of pipes that conduct the separated steam from each well to the power plant is shown in Fig. 4 .

The principal followed for transporting

steam is :that of connecting "feeder" pipes to the "principal branches", by which the steam is conducted to the power plant.

Table 7 lists the wells

that feed each principal branch and the amount of steam that is carried by each.

h e m i c a l c o m p o s i t i o n o f t h e steam i s shown i n T a b l e 6 .

The

The d i a m e t e r s of t h e p i p e s a r e 12 t o 40 i n c h e s , w i t h p i p e s o f 1 6 , 18, and 32 i n c h e s p r e d o m i n a t i n g . (Table 8 ) .

The t o t a l l e n g t h of t h e steam p i p i n g i s 24,240 m

The w e i g h t of t h e water and steam p i p i n g i n s t a l l e d a t C P - I

is

6,553 tons. O p e r a t i o n o f t h e s t e a m p i p e s y s t e m h a s been s i m p l e and i t s m a i n t e n a n c e easy.

The c o n d e n s a t e d r a i n s a r e t h e o n l y p a r t s o f t h e s t e a m t r a n s p o r t s y s t e m

t h a t r e q u i r e g r e a t c a r e and x a i n t e n a n c e , due t o t h e c o r r o s i v e n a t u r e of t h e water-steam m i x a t h i g h s p e e d i n t h e 2-inch d r a i n s ( e l b o w s ) .

F i g . 6 shows

one of t h e d r a i n s which a r e i n s t a l l e d a t r e g u l a r i n t e r v a l s i n t h e p r i n c i p a l branches.

The f u n c t i o n of t h e s e d r a i n s is v e r y i m p o r t a n t s i n c e i t p e r m i t s

e l i m i n a t i o n of t h e c o n d e n s a t e and e s p e c i a l l y t h e b r i n e c a r r i e d by the s t e a m . The normal q u a l i t y of t h e s e p a r a t e d steam a t t h e o u t l e t s of t h e s e p a r a t o r s t h a t a r e i n s t a l l e d i n e a c h w e l l i s 9 9 . 9 9 5 % ; t h e 0.005% d i f f e r e n c e i s b r i n e t h a t h a s t o be removed t h r o u g h t h e d r a i n s .

These d r a i n s a l s o s e r v e t o “ t r a p ”

t h e s o l i d s c a r r i e d by t h e s e p a r a t e d steam a s o x i d e s and m e t a l s u l f i d e s , and i n c e r t a i n c a s e s even sand from t h e w e l l s .

Before d r a i n s l i k e t h a t i n Fig. 6

were u s e d , c o n v e n t i o n a l steam t r a p s of t h e i n v e r t e d chamber t y p e were u s e d instead of h o l e s , without s a t i s f a c t o r y r e s u l t s .

That i s why t h e y were

r e p l a c e d by t h e p r e s e n t a r r a n g e m e n t w h i c h , a l t h o u g h a l l o w i n g s o n e l o s s of

steam, e l i m i n a t e s t h e c o n d e n s a t e and t h e b r i n e . C o r r o s i o n w i t h i n t h e s t e a m d u o t s h a s been minimal and i t i s e s t i m a t e d t o b e t h e same as t h a t measured d u r i n g c o r r o s i o n t e s t s done i n 1977, which

showed a r a n g e of 0.014 t o 0.030 m d y e a r .

T a b l e 9 shows t h e w a l l t h i c k n e s s e s

of t h e p r i n c i p a l b r a n c h e s t h a t were measured a t 600’m b e f o r e r e a c h i n g t h e c o l l e c t o r s of t h e CP-I power p l a n t .

The t a b l e shows t h a t t h e t h i c k n e s s e s a t

the lower part of the pipes are generally less than those in the upper and lateral positions. Using average values for the thicknesses, assuming that there was no corrosion in the other positions, it was estimated that the rate of corrosion in the power part of the pipe is 0.021 mm per yecr.

A good

practice that has prevented exeessive corrosion inside the steam pipes has been to keep the pipes pressurized whenever possible when they are not in operation, therebypreventhg air from entering them. Table 10 shows the pressure drops in some of the wells furthest fram the power plant, the greatest pressure drop being 2.6 kg/crn2 and the least only 2 0 . 2 kg/cm .

The longest pipe for steam transport was 3 , 6 8 0 m, corresponding

to well M-101. A l l the water and steam pipes have thermal insulation.

with insulation is 96,000 m

2

.

The area covered

Originally, it consisted of fiberglass padding

supported by chicken-wire and covered with monolithic cement.

The problem

with this kind of covering is that is is not sufficiently strong or flexible to withstand disintegration due to the environment. For these reasons, starting with units 3 and 4 the type of covering was changed, the monolithic cement being replaced by aluminum sheet, which h a s

g i v e n better results during the 6 years since it was installed. Fig. 5 shows some types o f supports used farthe steam pipes. Originally, rollers on carbon steel plates were used (Fig. 5 b ) , but their use Nas discontinued due to problems o f corrosion and contamination by earth and rocks because of their position at ground level.

Later, another type of support was used

(Fig. 5b) which was sufficiently separated from the ground, but its u s e was also discontinued because of probZems having t o do with keeping it in its original position on the teflon plate and because of the greater cost of materials.

F i n a l l y , t h e s u p p o r t s shown i n F i g . 5 , o r v a r i a n t s o f them, were a d o p t e d , i n which t h e d e s i g n was s i m p l i f i e d and moving p a r t s e l i m i n a t e d . R i g h t a n g l e " e x p a n s i o n c u r v e s ' ' a r e used t o a c c o u n t f o r e x p a n s i o n , h o r i z o n t a l o n e s i n t h e w e l l a r e a and v e r t i c a l i n t h e p l a n t , f o r r e a s o n s o f s p a c e and t o p e r m i t c i r c u l a t i o n of v e h i c l e s . Each " f e e d e r ' p i p e h a s a c u t o f f v a l v e b e f o r e t h e p l a c e where i t j o i n s t h e r e s p e c t i v e b r a n c h , and a n o r i f i c e p l a t e f o r m e a s u r i n g t h e r a t e o f f l o w o f t h e

steam.

To p r e v e n t w a t e r from b e i n g c a r r i e d , t h e r e i s a v a l v e n e x t t o t h e

steam d i s c h a r g e o f e a c h s e p a r a t o r .

When i t f l o o d s , i t s s p h e r i c a l f l o a t b l o c k s

t h e p a s s a g e o f w a t e r and steam t o t h e p i p e s and u l t i m a t e l y t o t h e t u r b i n e s . I f t h i s v a l v e d o e s n o t work, t h e r e i s p r o t e c t i o n i n t h e p l a n t ' s steam d r i e r s , which c l o s e t h e s h u t o f f v a l v e s a t t h e t u r b i n e i n l e t when t h e w a t e r l e v e l i s very high.

Two r u p t u r e d i s k s were a l s o i n s t a l l e d , w i t h d i f f e r e n t o p e r a t i n g

r a n g e s , a s a means of p r o t e c t i n g t h e s e p a r a t o r and t h e f e e d p i p e s ( F i g . 1 5 ) . One of t h e r u p t u r e d i s k s h a s a c u t o f f v a l v e t h a t i s n o r m a l l y open and makes

i t e a s y t o r e p l a c e t h e d i s k w h i l e t h e s e p a r a t o r i s p r o t e c t e d by t h e second d i s k , which h a s no c u t o f f v a l v e .

O r i g i n a l l y ( F i g . 1 4 1 , s a f e t y v a l v e s were

used i n s r e a d o f r u p t u r e d i s k s , b u t due t o problems o f c o r r o s i o n and m a l f u n c t i o n i n g , t h e y were e l i m i n a t e d and r e p l a c e d by t h e abovementioned r u p t u r e d i s k s .

A r a t h e r i n f r e q u e n t problem w i t h t h e d i s k s h a s been t h a t t h e y sometimes o p e r a t e a t p r e s s u r e s much lower t h a n t h e d e s i g n p r e s s u r e s .

This is explained

by t h e p r e s e n c e of c o r r o s i o n on t h e o u t e r p a r t o f t h e s t a i n l e s s s t e e l d i s k . T h i s problem h a s been minimized by c o v e r i n g t h e o u t l e t w i t h p l a s t i c s o as t o prevent environmental contamination. I n o r d e r t o r e g u l a t e t h e p r e s s u r e i n t h e steam t r a n s p o r t system t h e r e are c o n n e c t i o n s t o s i l e n c e r s , w i t h c o n t r o l v a l v e s o p e r a t e d by e l e c t r i c a l a c t u a t o r s

from t h e c o n t r o l room o f t h e power p l a n t .

These u n i t s a r e c a l l e d " r e g u l a t i o n

s y s t e m s " and a r e used when t h e r e i s low demand f o r e l e c t r i c i t y i n the s y s t e m , when t h e r e a r e r e j e c t i o n s o f l o a d , o r d u r i n g p e r i a d s o f major m a i n t e n a n c e . T r a n s p o r t o f medium and low p r e s s u r e steam ( 3 . 5 4 kg/cm2 m and 1 . 5 kg/crn2 m) f o r u n i t 5 i s done from t h e e v a p o r a t i o n p l a n t l o c a t e d n e x t t o s t h e pond.

The

l e n g t h of t h e p i p i n g i s 1 , 5 5 0 m and t h e d i a m e t e r s a r e 40 i n c h e s f o r t h e medium and 38 i n c h e s f o r t h e low. CONDUCTION OF SEPARATED WATER

The c r i e t e r i a f o r h a n d l i n g t h e s e p a r a t e d w a t e r i n t h e C e r r o P r i e t o Geot h e r m a l F i e l d h a v e had v a r i o u s s t a g e s .

O r i g i n a l l y , i t was s e n t t o t h e

e v a p o r a t i o n pond t h r o u g h u n i n s u l a t e d p i p e s t h a t were k e p t p r e s s u r i z e d by means o f o r i f i c e s n e a r t h e o u t l e t i n o r d e r t o r e d u c e t h e f o r m a t i o n of steam i n t h e p i p e and t h e r e f o r e t h e d e g r e e o f s u p e r s a t u r a t i o n o f s i l i c a , r a t e

of

i n c r u s t a t i o n , and p r e s s u r e d r o p , r e s u l t i n g i n a g r e a t e r c a p a c i t y f o r c o n d u c t i o n . Some p i p e s c o n t i n u e d t o o p e r a t e u n d e r t h e s e c o n d i t i o n s f o r more t h a n 6 y e a r s . When c o n s t r u c t i o n o f t h e E v a p o r a t i o n P l a n t w a s begun i n o r d e r t o make u s e o f t h e water t h a t was d r y i n g i n t h e pond, i t was n e c e s s a r y t o modify t h e p a t h , l e n g t h , and d i a m e t e r of t h e e x i s t i n g p i p e s , a r r i v i n g at the present arrangement shown i n F i g . 7.

I t was a l s o necessary t o i n s t a l l t h e r m a l i n s u l a t i o n i n o r d e r

t o p r e v e n t h e a t l o s s e s , which was n o t n e c e s s a r y o r i g i n a l l y .

Upon a r r i v a l a t

the Evaporation P l a n t ' s c o l l e c t o r s , it w a s possible t o use the regulation o r i f i c e s f o r t h e same p u r p o s e a s o r i g i n a l l y , w i t h t h e c o n d i t i o n t h a t t h e r e be p l a c e d i n each o r i f i c e 6-inch d i a m e t e r c o n n e c t i o n s f o r f i n e a d j u s t m e n t , s i n c e t h e c r i t e r i o n f o r d e s i g n of t h e o r i f i c e s w a s t h a t t h e y h a n d l e 50% of t h e f l o w and t h e r e m a i n d e r be r e g u l a t e d by means o f t h e v a l v e l o c a t e d i n t h e s a i d

connections.

When t h e E v a p o r a t i o n P l a n t o r any of t h e u n i t s i s n o t working, t h e water c a n b e d i v e r t e d from t h e c o l l e c t o r s t o t h e pond ( F i g . 1 6 ) . T a b l e 2 shows t h e q u a n t i t y o f s e p a r a t e d w a t e r produced i n e a c h w e l l , and T a b l e 4 shows t h e c h e m i c a l p r o p e r t i e s . The main problem i n t h e t r a n s p o r t of s e p a r a t e d w a t e r a t C e r r o P r i e t o I i s c a u s e d by s i l i c a d e p o s i t s on t h e w a l l s o f t h e p i p e s .

This i n c r u s t r a t i o n

g r a d u a l l y c a u s e s g r e a t e r p r e s s u r e d r o p s u n t i l i n sone c a s e s t h e p i p e c a n no l o n g e r be u s e d , making i t n e c e s s a r y t o c l e a n i t o r r e p l a c e i t . I t h a s been e x p e r i n e n t a l l y d e t e r m i n e d t h a t t h e r a t e s of i n c r u s t a t i o n i n

t h e water p i p e s and i n t h e equipment t h a t c a r r i e s w a t e r o r mix a t C e r r o P r i e t o depend m a i n l y on 2 f a c t o r s : t h e d e g r e e of s u p e r s a t u r a t i o n o f t h e s i l i c a i n r e l a t i o n t o t h e s o l u b i l i t y of t h e amorphous s i l i c a , and t h e pH.

Other f a c t o r s ,

which i n f l u e n c e t h e r a t e of i n c r u s t a t i o n t o a l e s s e r d e g r e e , a r e : t e m p e r a t u r e , s a l i n i t y , hydrodynamic e f f e c t s , q u a n t i t y o f suspended s o l i d s , and g a s c o n t e n t . On t h e o t h e r h a n d , b o t h s i l i c a s u p e r s a t u r a t i o n and pH depend on t h e c h a r a c t e r i s t i c s o f t h e f i e l d and t h e f o r m a t i o n s from which comes t h e f l u i d i n e a c h w e l l . T a b l e 11 and F i g . 8 show t h e h i g h e s t , r a t e s of i n c r u s t a t i o n measured i n a n d n s u l a t e d p i p e s f o r s e p a r a t e d w a t e r u p s t r e a m from t h e r e g u l a t i o n o r i f i c e . F i g . 9 shows t h e t r a n s v e r s e and l o n g i t u d i n a l c r o s s s e c t i o n s o f t h e 10-inch p i p e f o r s e p a r a t e d w a t e r , which i s a l m o s t 2,000 m l o n g and which had been c o n d u c t i n g w a t e r from w e l l M-91 t o t h e e v a p o r a t i o n pond.

The c a u s e o f such

s e v e r e i n c r u s t a t i o n was t h a t t h e p i p e had a n z a r i f i c e d i a m e t e r t h a t was t o o l a r g e on t h e o u t l e t s i d e , r e s u l t i n g i n r a p i d e v a p o r a t i o n o f t h e water i n t h e p i p e , e l e v a t e d s u p e r s a t u r a t i o n of s i l i c a , and t h e r e f o r e r a p i d i n c r u s t a t i o n . I n a n a t t e m p t t o s o l v e t h e problem o f i n c r u s t a t i o n i n t h e p i p e s f o r t h e s e p a r a t e d w a t e r , t h e FEC [ F e d e r a l E l e c t r i c i t y Commission].engaged t h e s e r v i c e s

of t h e I n s t i t u t e of E l e c t r i c a l R e s e a r c h t o s t u d y methods of p r e v e n t i n g i n c r u s t a t i o n and methods of c l e a n i n g i n c r u s t e d p i p e .

They c o n c l u d e d t h a t

i n t h e c a s e of b r i n e s w i t h h i g h s i l i c a c o n t e n t i t would be more economical t o t o p r e v e n t t h e f o r m a t i o n o f i n c r u s t a t i o n by l o w e r i n g t h e pH by a d d i n g acid t o the water.

I n t h i s way t h e r a t e of i n c i d e n c e of i n c r u s t a t i o n c o u l d

be r e d u c e d t o a n e d t e n t h ,

Nevertheless, i n order t o apply t h i s preventive

method i t i s n e c e s s a r y t o s o l v e t h e problem o f c o r r o s i o n t h a t i t s u s e w i l l occasion.

I n t h e c a s e of b r i n e s w i t h low s i l i c a c o n t e n t , t h e y c o n c l u d e d t h a t

i t i s more economical t o p e r m i t i n c r u s t a t i o n , and a f t e r 8 o r 10 y e a r s d e c i d e w h e t h e r o r n o t t o c o n t i n u e u s i n g t h e p i p e s and t h e n p r o c e e d t o c l e a n them o r r e p l a c e them.

Among t h e v a r i o u s c l e a n i n g p r o c e s s e s t h a t were t e s t e d ,

t h e y recommend c l e a n i n g w i t h a h i g h - p r e s s u r e water j e t , o r t h e c a v i t a t i o n method.

Another recommended method of c l e a n i n g w a s t h e u s e of s c r a p e r s ( " p i g s " ) .

None of t h e s e methods h a s been s u f f i c i e n t l y d e v e l o p e d and t h e i r r e s u l t s remain t o b e d e m o n s t r a t e d i n terms of economy.

To d a t e , t h e FEC h a s used o n l y

m e c h a n i c a l c l e a n i n g on a l a r g e s c a l e , which r e q u i r e s t h e p i p e s t o be c u t i n t o s h o r t s e c t i o n s , s t o o d u p r i g h t and s t r u c k i n o r d e r t o l o o s e n t h e i n c r u s t a tion.

Once t h i s h a s been done, t h e y a r e r e - i n s t a l l e d . F i g . 10 shows t h e e v o l u t i o n of t h e s u p p o r t s f o r t h e s e p a r a t e d - w a t e r p i p e s .

R o l l e r s were u s e d o r i g i n a l l y , i n o r d e r t o a l l o w t h e p i p e t o move ( F i g . l o a ) , b u t due t o t h e problems t h e y c a u s e d , t h e y c e a s e d t o be u s e d .

F i g . 10b and

1Oc show t h e t y p e s of s u p p o r t s t h a t r e p l a c e d t h e o r i g i n a l o n e s .

During

c o n s t r u c t i o n of t h e E v a p o r a t i o n P l a n t , supports:made o f - c h a n n e l - t y p e

4-inch

p i p e were in t h e lower p a r t o f t h e p i p i n g i n o r d e r p r e v e n t wear of t h e l a t t e r d u e t o movement.

CONDUCTION OF M I X

A t C e r r o P r i e t o I t h e r e h a s been e x p e r i e n c e w i t h t h e c o n d u c t i o n of mix a t d i f f e r e n t d i s t a n c e s and and u n d e r d i f f e r e n t c o n d i t i o n s .

The g r e a t e s t

d i s t a n c e t h a t m i x h a s b e e n t r a n s p o r t e d h a s been 1 , 8 0 0 m, from w e l l M-53 t o

M-39. F i g . 11 shows t h e p a t h s and d i a m e t e r s of t h e m i x p i p e s t h a t haveebeen used.

The c o n d u c t i o n o f 180 t o n / h o f mix from w e l l M-42 t o M-38,

o v e r 457 m

and w i t h 12-inch p i p e , has.coneinued-to,-be,carriedo u t f o r 9 y e a r s . L i k e t r a n s p o r t of s e p a r a t e d w a t e r , t h e main problem i n t h e t r a n s p o r t of mix i s t h e p r e s e n c e of i n c r u s t a t i o n s . T a b l e 12 shows t h e a v e r a g e a n n u a l c o n d i t i o n s under which t h e mix p i p e from w e l l M-53 t o M-39 o p e r a t e s .

A s t h e t a b l e shows, t h e c a u s e of s u s p e n s i o n

of c o n d u c t i o n of mix i n t h i s c a s e w a s i n c r u s t a t i o n i n t h e w e l l . o f t h e mix p i p e showed t h a t i t w a s n o t e x c e s s i v e l y e n c r u s t e d .

Inspection I t was c u t

1,300 m from w e l l M-53 and a t y p e of i n c r u s t a t i o n w a s found t h a t w a s v e r y d i f f e r e n t from t h e k i n d i n t h e w a t e r p i p e s ; i t had a v i t r e o u s a p p e a r a n c e , w a s v e r y h a r d , and was 1 . 2 5 cm t h i c k i n t h e upper p a r t and from 2 . 5 t o 3 . 7 cm t h i c k i n t h e lower p a r t of t h e p i p e . The p r i n c i p a l a d v a n t a g e s of c o n d u c t i n g mix i n s t e a d of water and steam s e a p a r a t e l y are t h e following: a ) Less p i p i n g i s r e q u i r e d . b ) The i n s t a l l a t i o n s i n t h e w e l l a r e s i m p l e r . c ) Less environmental p o l l u t i o n , s i n c e a s m a l l e r area i s r e q u i r e d . d ) The o p e r a t i n g and m a i n t e n a n c e c o s t s of s e p a r a t i o n - e v a p o r a t i o n u n i t s

i s l e s s when t h e y a r e c o n c e n t r a t e d a t a s i n g l e s i t e and c a n be equipped w i t h remote c o n t r o l systems and i n s t r u m e n t s .

One of the p r i n c i p a l d i s a d v a n t a g e s o f t h e t r a n s p o r t o f mix i s l o s s o f a v a i l a b i l i t y o f t h e w e l l d u r i n g t h e t i m e when the mix p i p e h a s t o b e c l e a n e d or replaced. CONDUCTION OF GASSES

When o p e r a t i o n s began a t theTCP-I Power P l a n t , t h e i n c o n d e n s a b l e g a s s e s were d i s c h a r g e d a t t h e s i t e i t s e l f t h r o u g h 40 m h i g h chimneys.

Nevertheless,

a t t i m e s a t m o s p h e r i c c o n d i t i o n s a r e such t h a t t h e H S c o n c e n t r a t i o n a t t h e 2

s i t e i n c r e a s e s g r e a t l y , and a l t h o u g h i t h a s n o t r e a c h e d d a n g e r o u s l e v e l s , i t

was t h o u g h t a p p r o p r i a t e have t h e d i s c h a r g e n e a r t h e e v a p o r a t i o n pond.

To

do t h i s , epoxy r e s i n p i p e r e i n f o r c e d w i t h f i b e r g l a s s , 26 i n c h e s i n d i a m e t e r and 1,400 m l o n g w a s d e s i g n e d and i n s t a l l e d .

I t s p a t h i s shown i n F i g . 1 2 .

When i t began t o o p e r a t e , f a n s were u s e d i n t h e p l a n t i t s e l f t o h a n d l e the gasses.

I n a s h o r t t i m e t h e y ceased t o o p e r a t e because of t h e e x c e s s i v e

c o r r o s i o n o f t h e i r componenCs.mixture extremely agressive.

The c o m b i n a t i o n o f H S and oxygen makes t h i s 2

The f a n s w e r e no l o n g e r u s e d , s i n c e t h e d i s c h a r g e

p r e s s u r e of t h e l a s t s t a g e o f t h e g a s e x t r a c t i o n s y s t e m w a s s u f f i c i e n t f o r d i s c h a r g e t h r o u g h t h e abovementioned p i p e . t h e pond i s 25 t o n / h .

The q u a n t i t y o f g a s s e s s e n t t o

T a b l e 13 shows t h e a n a l y s i s o f t h e i n c o n d e n s a b l e g a s s e s .

SEPAIIATORS, SILENCEXS, AND VARIOUS OTHER EQUIPMENT F i g . 13 shows t h e p r i n c i p a l equipment used a t C e r r o P r i e t o I , and F i g . 14 and 15 show t h e equipment l a y o u t i n t h e s e 2 c a s e s , b e f o r e and a f t e r t h e 5 t h unit.

Due t o t h e i r s i z e and number, 54-inch Weber s e p a r a t o r s a r e u s e d , whose

o r i g i n a l d e s i g n w a s s i m i l a r l y employed i n W a i r a k i , N . Z . ,

although a t Cerro

P r i e t o t h e y underwent some c h a n g e s i n o r d e r t o a d a p t them t o t h i s f i e l d .

The

most n o t a b l e changes a r e t h e h i g h t of t h e c o n c e n t r i c p i p e , t h e water d i s c h a r g e p o s i t i o n s , and t h e change from a r e c t a n g u l a r t o a c i r c u l a r c r o s s s e c t i o n a t t h e

separator i n l e t .

The h e i g h t o f t h e i n t e r i o r c o n c e n t r i c p i p e was i n c r e a s e d '

i n o r d e r t o i n c r e m e n t t h e q u a l i t y of t h e s e p a r a t e d steam and t h e d i s c h a r g e o f water a t t h e lower p a r t , so as t o improve c o n t r o l of t h e l e v e l i n t h e s e p a r a t o r and t o p r e v e n t i n c r u s t a t i o n i n t h e w a t e r

chamber, as t h i s p r o d u c e s

f l o o d i n g and w a t e r i n t h e s t e a m . The a d v a n t a g e o f t h e changes w a s a p p a r e n t immediately i n t h e b e t t e r q u a l i t y of s e p a r a t e d steam and t h e l e s s f r e q u e n t need t o c l e a n t h e t u r b i n e s , whose vanes and diaphragms had c l o g g e d w i t h t h e s i l i c a d i s s o l v e d i n t h e steam-carried water.

The a v a i l a b i l i t y c o e f f i c i e n t of t h e t u r b i n e s w a s

increased. T a b l e 14 shows t h e q u a l i t y o f steam i n t h e CB-I w e l l s . R e c e n t l y , w i t h t h e d i s c o v e r y of a d e e p e r i a n d more p o w e r f u l d e p o s i t i n t h e same zone a s t h e f i r s t w e l l s f o r CP-I,

t h e s i z e of t h e 5 4 ? i n e h - s e p a r a t o r s

was found t o b e i n s u f f i c i e n t , b e i n g l i m i t e d t o t h e s e p a r a t i o n of 250 t o n / h o f mix.

T h i s made i t n e c e s s a r y t o b u i l d l a r g e r s e p a r a t o r s (78-inch d i a m e t e r )

i n o r d e r t o be a b l e t o u s e t h e g r e a t e r p r o d u c t i o n c a p a c i t y o f t h e deep w e l l s . One o f t h e p r i n c i p a l problems i n t h e o p e r a t i o n of t h e s e p a r a t o r s i s t h a t when t h e p r e s s u r e i n t h e steam p i p e s y s t e m i s v a r i e d , when t h e v a l v e s o f t h e r e g u l a t i o n s y s t e m a r e opened o r c l o s e d , t h e water l e v e l s i n t h e s e p a r a t o r s v a r y c o n s i d e r a b l y , a t t i m e s f l o o d i n g and c o n s e q u e n t l y c a r r y i n g w a t e r .

For

t h i s r e a s o n , i t w a s d e c i d e d t o o p e r a t e t h e s e p a r a t o r s a t a v e r y low l e v e l o r none, t h e l o s s o f steam o r i g i n a t i n g i n - t h e d i s c h a r g e o f w a t e r .

From t h e

above was deduced t h e a p p r o p r i a t e n e s s o f d e s i g n i n g a r e g u l a t i o n s y s t e m t h a t keeps t h e p r e s s u r e i n t h e s t e m branches c o n s t a n t . T h e r e a r e 41 s e p a r a t o r s o p e r a t i n g a t C e r r o P r i e t o , 3 2 of which a r e f o r p r o d u c t i o n o f p r i m a r y steam, 3 f o r mediiim, and 6 f o r low.

Othe

important parts of the installation at the well platform are the

silencers. They were originally used according to the same principle as at Wairakei, N . Z .

Nevertheless, their capacity was insufficient and it was

necessary to design the types shown in Fig. 13s and 13h, with capacities for handling 300 and 500 ton/h o f mix. The principal problem in regard to the silencers is the elimination of incrustations, which is done mechanically or with high-speed jets of water. New cleaning methods are under study. of

At CB-3-theFe are 58 concreee silencers

the types shown in Fig. 13g and 13h. To arrive at these designs it was

necessary to test various types of materials for the chimneys, including carbon steel, wood, and finally polyester resin reinforced with fiberglass. Portable metal silencers are frequently used in the evaluation of new wells.

At the CP-I field, the wells frequently carried sand from the producing formation, which had to be detected in time to prevent its being carried by the steam.

In order to detect the presence of sand, the samplers shown in

Fig. 14 and 15 were used.

As the illustrations show, no expansion joints

were used between the well and the separator. They were used originally, but due to maintenance problems they ceased to be used; the practice of installing

the bend for7the inlet to the separator under the final operating conditions of the well was used. When it is not necessary or not possible to conduct the separated water through pipes, it is discharged into open channels, which carry it to a point near the evaporation pond, into which it is pumped.

It is frequently necessary

to dredge these channels, where great amounts of silica are deposited. CONCLUSIONS

At Cerro Prieto I, 10 million MWh have been generated and 300 million tons

of geothermal fluid have been produced.

The length of the present system of

12- to 40-inch steam pipes is 24,240 m.

The system of 8- to 16-inch water

pipes is 46,500 m in length.

There are 32 wells, 41 separators, 58 silencers,

7 steam driers, and 290 8- to 30-inch valves.

Corrosion in the the pipes and

surface equipment has not been a serious problem.

The principal maintenance

problem has been the cleaning of incrustations and sediment of silica in the pipes, equipment, and channels. Frequent maintenance is necessary to maintain the capacity of the water pipes, the separators, .and the channels. The pipes of the wells, and in some cases the deposit itself, have also been affected by incrustation. Even the small amounts of silica carried by the separated steam are deposited in the turbines, reducing their capacity. Given the extensive experience gained during Cerro Prieto 1's 12 years, in the transport of geothermal fluids, it is advisable to take advantage of it in the design of future geothermal projects for fields in which liquids predominate.

...

- .--

.,. . . ... .

KEY for TABLES and FIGURES

Table 1. Annual amounts of electricity generated and energy extracted from 1973 to 1984 at the Cerro Prieto I Geothermal Field. 1) Year 2) Electricity generated 3) Production of mix 4) Energy extracted 5) Specific heat consumption Table 2. Wells of Cerro Prieto I Plant (March 1985). 1) Well 2)

3) 4) 5) 6) 7)

Depth Pressure at well head Separation pressure Steam flow Water flow Enthalpy of mix

Table 3 . Average characteristics of wells. 1) Average depth of wells 2) 3)

4)

5)

Average enthalpy of mix produced Average temperature of deposit Total solids dissolved in seaparated water at atmospheric pressure Non-condensable gasses in separated steam (%by weight)

Table 4. Chemical composition of the separated water from Cerro Prieto I wells (March 1984) 1) Pressure at well head 2) Separation pressure 3)

4)

Concentrations The samples were taken at the separation pressure and the data presented under atmospheric conditions.

Table 5. Chemical composition (mg/l) and physical properties of the separated water at atmospheric pressure from wells M-14, M-30, M-91, and M-53 of Cerro Prieto (November 1980).

1) 2) 3) 4)

m e Chlorides Sodium Potassium

5)

Silica

6)

7)

Calcium Carbonates

8)

Bicarbonates

Cesium 10) Bromides

9)

11) 12)

Lithium Boron

Strontium 14) Rubidium 15) Sulfates

13)

16) Fluorides 17) Manganese 18)

Iron'

19) Arsenic 20) Iodine 21) Magnesium 22) Copper 23) Chromium 24) Aluminum 25) 26)

Zinc Silver

27) 28) 29)

Palladium Cadmium Sulfides

30)

Dissolved solids

31)

Conductivity 32) Density 33) Acidity 34)

Symbol

Table 6 .

Chemical composition of the separated steam from Cerro Prieto I wells (May 1982).

1) 2)

3) 4)

Well Pressure at well head Separation pressure Components (%by weight)

Table 7. Wells and steam 1) Branch

branches of Cerro Prieto I (March 1985).

3)

Wells connected per branch Quantity

4)

Identification

5)

Steam flow

2)

Table 8 .

Diameters and lengths of steam and water pipe at C.P. I.

1)

Diameter (inches)

2)

Installed length (m) Steam pipe Water pipe

3)

4)

Table 9. Thickness of pipe wall, measured in the branches of Cerro Prieto I. 1) 2) 3)

4) 5) 6)

7) 8)

Branch Diameter (inches) Identification Thicknesses (inches) Upper dome Lower dome Right side Left side

Table 10. Pressure in the separators of the farthest wells of C.P. I. 1) 2)

Branch Well

3)

Pressure in separator

4) Pressure of collector at plant 5 ) Well - collector distance

Table 11. Incrustation observed i n pipes f o r separated water a t Cerro P r i e t o I (May 1979) 1)

Well

2)

T i m e of operation (years)

3)

Thickness of i n c r u s t a t i o n (mm)

4)

Rate of i n c r u s t a t i o n (mm/year)

Table 1 2 . Average annual operating conditions of mix pipe from well M-53 t o M-39. 1)

Year

2)

Pressure a t well head

3)

Pressure i n well M-39 separator

4)

Mix production

5)

Enthalpy

Table 13. Analysis of non-condensable gasses.

1)

Compound

2)

% by weight

3)

Ethane

4)

Propane

5)

Isobutane

6)

n-butane

Table 14. Quality of separated steam i n wells of Cerro P r i e t o I (January 1985). 1)

Well

2)

Pressure

3)

Well head

4)

Separator

5)

Steam production

6)

Quality of steam

Fig. 1.

Locations of wells at C.P. I Geothermal Field

1)

C.P. I Power Plant

2)

C.P. II Power Plant

3)

C.P. 111 Power Plant

4)

Evaporation pond

5)

Volcanic lake

6)

Delta Canal No. 1

7)

Existing wells, March 1985

8)

Scale

9)

Public grazing land

10) Public grazing land

Fig. 2 .

Characteristic production curves for 2 wells of C.P. I.

1)

gel1 M-l9A, ?lay 1976

2)

Depth of open interval

3)

Well head pressure

4)

Overall volume of flow

5)

Well E-2,

April 1981

Fig. 3 . Flow diagram of Cerro Prieto I. 1) Foundation 11) 2)

Consolidated sediments

3) 4)

Unconsolidated sediments Mix

5)

Primary separator

6)

Separated water

7)

High pressure steam

8)

Units 1, 2, 3 , and 4

9)

To condensers

10)

Unit 5

Separators of instantaneous evaporation plant

12) Y e d i m pressure 13)

Water tank

14)

Low pressure

15)

Xedium pressure steam

16)

Water tank

17)

Low pressure steam

18)

Evaporation pond

Fig. 4 . 1)

Arrangement of steampipes at Cerro Prieto I.

C . P . I Geothermoelectric Power Plant

5.

Types of supports used for steam pipes.

Free support (1973) Plate Guided support (1979) Plate Guides Teflon Free support (1982) Channel Fig. 6 .

Steam pipe drainage system,

1)

Steam pipe

2)

Drain

Fig. 7 . 1)

Arrangement of hot water pipes at C.P. I.

C.P. I Geothermoelectric Power Plant

Fig. 8.

Incidence o f incrustation observed in separated water pipes of

C.P. I ( I I E Report, 1981). 1)

Concentration of silica in brine (mg/l>

2)

Incidence of incrustation (mm/year>

Fig. 9.

Distribution o f incrustation depositied in the separated water pipe of well M-91 ( I I E Report, 1981).

1)

Length of pipe (meters)

Types of supports used for separated water pipe.

10.

Guided supports for pipe beds (1973) Roller Bracket Guided and free supports (1978) 2:'

0 bracket o n l y for guided supports

0 pipe 2%'' 0 pipe

4"

Guided and free supports (1979) 2" @ bracket only for guided supports

4''

0

Fig. 11.

pipe. Pipes for conduction of mix.

1)

C.P. I Seothermoelectric Power Plant

2)

Railroad

Fig. 12. Pipes for conduction of non-condensable gasses.

1)

C.P. I Geothermoelectric Power Plant

2)

Evaporation pond 13. Principal equipment used for handling geothermal fluids at C.P. I. "Webre" type separator with integral water tank (Units 1, 2, 3, and 4 ) Separator with external water tank (Unit 5 ) Horizontal separator (experimetab] Horizontal separator (adaptable for pipe) Humidity remover (Unit 5) "Centrifix" humidity remover (Units 1, 2 , ' 3 , Original silencer Present silencer

and 4 )

Fig. 14.

Original arrangement (1973) of the principal installations comprising the surface equipment of a C.P. I geothermal well.

Upraise

15)

Separated water discharge to evaporation pond

Separator

16)

Offset valve to siiencer

Rupture disk

17)

Silencer

Level indicator

18)

Open channe1

Steam sample outlet

191

Sp i1lway

Water discharge Relief valve

201 Mix discharge 21) Pressure gauge

Globe valve

22)

Outlets for measuring differential pressure

23)

Drains

24)

T o evaporation pond

25)

To C.P. I Power Plant

Valve shaft

Orifice plate

I

Cutoff valve 12)

Principal branch

13)

Sand sampler

14)

Offset valve

Fig. 15.

Present arrangement (1985) of the principal installations comprising the surface equipment of a C.P. I geothermal well.

Upraise

15)

Separated water discharge to evaporation pond

Separator

16)

Silencer

Rupture disks

17)

Open channel

Level indicator

18)

Spillway

Steam sample outlet

19)

Mix discharge

Separated water discharge

20)

Globe valve drain

Pressure gauge

21)

Condensate drain

9)

Globe valve

22)

Outlets for measuring differential pressure

10)

Orifice plate

23)

11)

Cutoff valve

Orifice plate with branch for fine adjustment (by-pass)

12)

Principal branch

24)

To C.P. I Power Plant

13)

Sand sampler

14)

Offset valve to silencer

Valve shaft

16. Flow diagram of the instantaneous evaporation plant. T o Unit 5

Separated water Separated .waler?Medium pressure steam Unit 1 and 2 collector Unit 3 and 4 collector Medium pressure evaporator Medium pres sure evaporator Medium pressure evaporator Low pressure steam Medium pressure accumulator tank Medium pressure accumulator tank Medium pressure accumulator tank Low pressure evaporators Low presssure accumulator tank Low pressure accumulator tank Low pressure accumulator tank Evaporation pond

Tabla 1 .

2 I

Valores anuales de generaci6n e l i c t r i c a y e x t r a c c i 6 n de e n e r g i d , de 1973 a 1984 en e l Campo Geotgrmico de Cerro P r i e t o I .

3

Generaci6n elCctri c a

Gwh

AiiO

Producci6n de mezcla ton

x 10

qEnergia extraida

Consumo e s p e c i f i c o de c a l o r 3

Kcal x 10 1 2

Kcal/Kwh x

10

~

1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984

193 463 518 579 59 2 598 1019 91 5 964 1267 1221 1264

10.2 18.7 19.1 22.1 23.8 22.0 38.2 33.1 33.0 38.7 39.5 36.2

Total:

9593

334.6

Tabla 2.

2

/

PO 20

E- 1 E- 2 E- 4 E-6 E-7 M- 1OA M-11 M- 14 M- 19A M- 20 M-21A M- 25 M- 26

M- 29 M-35 M-42 M-43 M-45 M-47 M- 50 M-51 M-73 M- 79 M-84 M-90 M-91 M-102 M-103 M-104 M-114 M-120 M-130

3.3 6 -0 6.1 7.1 7.6 7.1 12.3 10.6 10.6 12.4 12.7 11.6

17.1 13.0 11.8

12.3 12.8

11.9 12.1

11.6 1 1 .o

9.8 10.4 9.2

107.4

11.2

Pozos i n t e g r a d o s a la P l a n t a de Cerro P r i e t o I . Profundidad.

(m) 1782 1946 1766 2567 21 19 1801 1212 1293 1263 1377 1295 1381 1266 1295 1286 1311 1246 1390 1727 1250 1567 1883 181 1 1691 1379 2294 1990 2008 1725 1692 1627 2096

3

Presio'n e n

l a cabeza

2

(kg/cm )m 12.30 25.40 42.18 10.54 45.69 56.90 9.00 28.41 7.38 31.64 10.54 20.04 9.84 6.32 7.87 11.9 6.46 6.67 58.34 10.54 16.50 23.90 15.46

8.22 6.88 10.40 7.03 16.87 18.55 6.33 7.03 23.55

Y P r e s i 6 n de s e p a r a c i6n

r Fvapor lujo

2

(ton/h)

6.00 6.67 7.17 7.03 8.43 7.31 6.39 6.32 7.38 8.15 6.67 7.94 7.10 6.32 6.18 6.11 6.46 6.04 6.88 7.17 6.95 6.67 6.74 7.38 6.60 7.03 6.81 6.81 8.15 6.04 6.82 7.63

28.4 34.9 59.4 34.3 88.7 54.9 17.6 32.0 57.5 35.0 13.2 40.5 24.0 20.9 39.7 40.4 18.7 13.1 34.6 58.4 70.9 53.6 47.1 70.1 28.5 43.7 27.9 27.1 75.1 19.8 34 .8 56.9

( W a n )m

(Marzo 1985)

6 Flujode 7 Entalpia

de

agua

.

(ton/h) 25.9 46.5 51.4 80.5 134.1 58.7 47.6 101.6 144.9 113.4 25.4 104.0 68.6 8 3 .O 109.0 130.8 55.4 22.0 70.1 169.7 138.2 98.2 100.1 25.4 84.8 8 3 .8 3.9 14.1 18.8 65.6 8 2 .O 45.6

de mezcla

(KJ/Kg) 1772 1591 1818 1331 1555 1709 1261 1197 1306 1222 1414 1302 1251 1116 1250 1186 1226 1469 1392 1245 1412 1436 1369 2226 1225 1421 2506 2065 2365 1174 1325 1864

Tabla 3.

C P I11

1635

2500

2200

3

E n t a l p i a promedio de l a mezcla producida (KJ/Kg)

1423

1510

1632

3

Temperatura promediodel Yacimiento ( " C )

300

328

34 5

So'lidos t o t a l e s d i s u e l t o s en e l aqua separada a presidn atmosfirica (mg/l)

25000

33000

3 2 500

Gases incondensablesen vapor separado ( % e n peso)

1.4

0.0-1.2

0.8-1.2

1 Pozo

E-4 E- 6 E-7

M-IOA M-14

M-21A M-35 M-51 M-84 M-90 M-9 1 M-103 M-105 M-114 M- 120

4

CP I1

Profundidad promedio de pozos ( m ) .

Tabla 4.

*

CP I

/

<

-

C a r a c t e r i s t i c a s promedio de pozos.

Composici6n q u h i c a d e l aqua separada de pozos de Cerro P r i e t o 1 !Marzo 1984).

P r e s i d n e n Presidn de l a cabeza >separaci6n 2 2 Kg/m )m (Kq/cm ) m 56.2 12.0 68.8 64.5 30.6 7.7 8.8 16.9 8.8 7.7 9.8 8.8 9.1 7.6 17.9

8.5 8.4 9.5 9.0 7.3 7.5 7.7 8.1 8.4 7.6 7.8 8.1 8.6 7.5 9.5

4 o n c e n t r a c i o n e s (mq/l) pH

6-6 7.2 7.0 6.2 6.8 7.2 8.1

7.1 7.0 7.6 7.1 6.9

7.3 7.8 6.7

Na 10972 10909 12319 9856 4679 5761 4227 6100 0485 4562 0021 6104 9742 71 10 10151

K

Li

Ca

3066 2959 3449 2912 804 1263 782 1477 2958 926 2704 1405 2279 1357 2946

29 29 33 31 12 16

414 509 489 373 241 256

10

15s

16 29 12 27 15 25 17 30

201 470 158 373 191 531 432 382

C1

20299 20316 23274 18587 8335 10232 1503 10795 19797 7886 18547 10795 17798 13281 18815

HC03 49 80 47 76 127 117 71 100 63 76 71 92 49 72

51

STD

Si02

36435 37138 4 1624 33300 14779 18414 13413 19039 35463 14309 34003 19445 32095 23210 33762

1002 1094 1266 1183 693 838 706 927 925 708 1308 1069 9 38 718 1112

Las muestras fueron tomadas a la presidn de separaci6n y 10s datos reportados a condiciones atmosf6ricas.

Tabla 5 .

Especie

composici6n quimica ( m g / l ) y propiedades f i s i c a s del aqua separada a l a presi6n atmosfgrica de 10s pozos M-14, M-30, M-91 y M-53 de Cerro P r i e t o (noviembrede 1980). 3~Shtx310

Y Cloruros c19 Sodio Na y Potasio K Silice Si02 C Calcio Ca 7 Carbonatos COT Bicarbonatos HCOf 9 Cesio CS /o Bromuros Br/f t i t i o Li f Y Boro B I J Estroncio Sr r Y Rubidio Rb 19 Sulfatos so: / I Fluoruros F17 Manganeso Mn ,q F i e r r o Fe 4 Arsinico AS 10 IOdO I si Magnesio Mg w Cobre cu L~ Cromo cr fl Aluminio A1 =rZinc Zn Plata A9 u Paladio Pd r~Cadmio Cd 5.$ Sulfuros s= t r S6lidos Disuel tos STD 31 Conductividad umhos 1 L Densidad g/ml J J Acidez PH

Tabla 6 .

0.04

0.16 0.15 0.03 1.4 21,800 20,000 1.008 8.5

M-30

M-9 1

M-53

14,200 7,350 1,520 975 528 22.2 11.3 1.7 33.5 18.7 17.4 5.6 7.4 13.0 1.3 2.5 2.4 0.47 0.58 0.66 0.06 0.15 0.15 0.03 0.13 0.20 0.03 1 .8 26,522 23,000 1 - 0 11 8.3

19,130 9,950 2,585 1,241 432 12.7 14.1 2.6

18,105 9,240 2,790 1,301 406 16.2 8.23 2.4

23.5 16.5 4.1 14.0

25.1 25.3 2.5 10.4

-

-

-

-

-

-

1.4 3.0

5.5 2.8

1.4 0.07 0.62 0.10 0.03 0.07 0.24 0.07 1.3 36,867

1.6 0.08 0.39 0.20 0.06 0.26 0.06 1.3 34,902

1.019 8.4

1.016 8.4

-

-

-

0 -06

-

-

Composici6n quimica d e l vapor separado e n pozos de Cerro P r i e t o I

PresiBn

1 Po20

M-14 11,242 6,090 1,060 81 3 342 28.9 13.5 1.3 17.5 14.5 17.2 5.2 4.5 11.0 2.4 0 -43 1.7 . 1.5 0.59 1.5 0.07 0.12 0.10

en l a cabeza (Kg/cm2)m

'Presi6n

Componentes

de sep5 raci6n. (Kg/cm2)m

H20

co2 H2

(%

( ~ a y o1 9 8 2 ) .

en peso) He

Ar

CH4

NH3

H2

N2

10-2

10-2

10-3

10-3

lo-3

1o

- ~

-6 10

M-21A

19.0

6.4

98.13

1.75

8.1

1.8

10.3

3.3

3.7

1.3

0.0

M-3 1

7.0

6.5

98.62

1.29

6.3

1.8

8.0

3.2

4.7

1.2

1.7

M-51

9.0

7.7

98.37

1.52

6.9

2.2

7.6

4.1

7.0

1.8

4.2

M-104

8.1

7.1

96.61

3.19

13.6

4.6

8.0

11.6

6.4

1.5

0.0

M-105

9.2

8.2

99.17

0.77

3.9

1.5

4.1

2.8

5.8

1.5

3.4

M-120

36.9

8.8

98.20

1.68

8.1

1.9

12.4

4.1

4.3

1.1

6.0

E- 3

31.5

6.7

98.20

1.66

7.9

1.3

14.2

4.0

4.8

1.2

4.3

Tabla 7 .

/

Relaci6n de pozos integrados a 10s ramales de vapor de Cerro P r i e t o I (Marzo 1 9 8 5 ) .

2-

Ramal

3

(NO.)

7 Flujo

Pozos conectados por ramal

f

Cantidad

Identificaci6n

(Ton/H)

1

5

M-1OA, M-130

2

5

M-14, M-19At M-25, M-29

M-11,

M-42,

de Vapor

M-114,

167.5

,

169.6

M-43 2

M-20 y M-26

4

4

E-1,

5

4

E-4, M-47, M-50, M-90

6

3

M-51,

7

5

E-2,

M-102, M-4 2 0

0

4

E-6,

3

Tabla 0 .

M-21A,

59.0 M-35,

94.4

M-45

199.4

M-04, M-91

104.7

M-103,

E-?, M-73,

M-104,

M-79

221 - 9 223.7

D i h e t r o s y longitudes de tuberfas de vapor y agua en C.P. I .

IL /

Dihetro (Pulgadas)

8 10

3

Longitud I n s t a l a d a (m) Tuberfa de vapor

-

S L T ~ e r fde a agua 19300

17900

12

1160

6680

16

41 00

2620

10

4400

-

20

1900

-

24

1050

26

1550

30

1920

32

3170

-

34

1890

-

38

1550

-

40

1550

-

Total:

24240

46500

Espesores de pared de t u b e r i a , medidos e n 10s ramales de Cerro P r i e t o I .

Tabla 9 .

Ramal Y

NO.

Es$esores

3

Dibetro (pulgadas)

34 34 34 34

xs

30

STD

32 32 32

STD STD

xs STD

.544 .525 -526 .534 -413 .402 -411 -378

t

~ozo

Presi6n en e l Separado r (Kg/cmz)m

M-11 M-43 M- 26 M-45 M-90 M-9 1 M- 104 E-6

Tabla 1 1 .

7.5 8.6 8.8

.553 .540 -525 -539 -424 .411 .406 -388

.546 .532 * 543 .546 .433 .417 -425 -377

JDistancia Pozo-Cf !lector

(m) 1430 1945 1165 1815 2955 231 5 2525 2435

Incrustacidn observada en t u b e r i a s de aqua separada (Mayo 1979) en Cerro P r i e t o I .

Pozo

M- 1 9A M- 5 M-11 M-21A M- 8 M- 26 M-14

Costado Izquierdo

6.1 6.1 6.1 6.1 6.2 6.2 6.3 6.2

t T i e m p de

~~

0

Costado Derecho

'Presi6n d e l Colector e n Planta (Kg/cm2) m

6.9 6.3 6.6 6.7 6.7

Sio2 -

(pulgadas)

7

Presi6n en 10s separadores de 10s pozo mas lejanos de C.P.

3

'

Domo I n f e r i o r

.565 -544 .530 .543 .413 .434 .404 .378

xs xs

Ramal

6

Domo Superior

&dula

Tabla 10.

'

5

operacidn (aiios)

3

Espesor de incrustaciones

Velocidad de incrustacidn

(m)

(mm/aiio)

.

1100 1000 900 900 800 850 700

4.2 6.2 6.2 4.1

5.3 5.3 2.1

19.1 19.1 12.7 6.4 6.4 4.8 1.6

4.5 3.1 2.1

1.4 1.2

0.9 0.6

I.

-

Tabla 12.

/

.

...

....

......,.

P r e s i 6 n en s e p 5 'Produccibn rador pozo M-39 mezcla

(kg/cm2)m

rEntalpia

(kg/an 2 1 m

ton/h

kcal/kg

6.7

114.0

367

1978

11 .o

1979

10.0

6.5

86.0

359

1980

9.1

6.5

70.0

3 50

1981

8.6

6.8

51 .o

3 30

1982

7.9

7 .O

32.0

31 5

T a b l a 14.

E- 1 i

E-2 E-6 E- 7 M- 1OA M-4 1 M-14 M- 19A M- 20 M-21A M-25 M-26 M-35 M-42 M-43 M-45 M-47 M-51 M-73 M-79 M- 50 M-91 M-102 M- 103

'

M-104 M-105 M-114 M-120 M- 130 M-169

...

.........

3 Cabeza 3 20 3 34 150 650 820 110 414 100 4 60 190 280 140 120 175

86 100 830 216 305 228 103 145 99 21 2 260 325 91 2 30 91 870

yseparador 106.5 103 111 145 121 96 98 95 92 10 8 120 104 105 102 73

98 110 111 115 114 100 109 97 105 127 115 90 124 89 110

Produccio'n de vapor

tonh

. ...

.....

,...-..-

A n d l i s i s d e gases incondensables

1 compuesto

2

%

en peso

5.29 58.44 2.32 0.03122 I .7895 26.0086 0.1086 0.0014 0.0003679 0.00041 5 0.0003462

Calidad d e l vapor separado en pozos de Cerro P r i e t o I (Enero 1985)

* LrPe s i 6 n ( kg/cm2) m

PO20

..

Tabla 13.

Condiciones promedio anuales de operaci6n de la t u b e r i a d e mezcla d e l pozo M-53 a 1 M-39.

?Presi6n en l a cabeza Aiio

~

6

Calidad de vapor (2)

61 - 5 30.1 34.1 9 1 .o 57.4 18.3 31.1 57.6 34.5 11.9 41.1 23.7 39.8

99.998 99.995 99.998 99.992 99.986 99.997 99.997 99.998 99.993 99.998 99.997 99.998 100.000

39.1

100.000

18.8 14.2 42.6 67.4 51.7 47.5 31.3 53.9 27.0 25.8 76.6 29.1 21 - 5 46.9 37.9 33.2

100.000 99 * 9 9 8 99.999 99.990 99.999 99.994 99.992 99.991 99.983 99.993 99.996 99.993 100.000 99,996 100.000 99.992

,. ..

!

-'\

l

o

I

e ~(r. i

'.-2! '

Ql

r

.eat . J Figura 1 .

Localizaci6n de p z o s en el C a m p o Geot6rmico de C . P .

1.

.a. , .

Fig. 2 .

Curvas caracteristicas de producci6n para 2 pozos de C.P. 1

Sedlnenma

Baaamento

bA Figura 3 .

COYOENSAOORES

Diagram de flujo d e Cerro Prieto I.

c).- SOPORTE U B f E ( r s e 2 )

Figura 5 .

Tipos de soportes empleados para tuberias de vapor

6)

T U B E R I A DE VAPOR

Fiqura 6 .

Sistema de drenado e n tuberfas de vapor.

PARADORES DE PLANTA EWPORACMJU I W T A N T A M A

n

ALIA PRESION

kA

Figura 3 .

CONDENSADORES

Diagrama d e f l u j o de Cerro Prieto I.

d

@

al- SOPORTE U B R E (1973)

e).- SOPORTE UBE(Jse2)

Figura 5 .

T i p s d e s o p o r t e s empleados para t u b e r z a s d e vapor.

@7 r U B E R l A DE V A P O R

.

. .-

Fiqura 6 .

..

.

. -. . .. -..

..

.

Sistema d e drenado en t u b e r f a s d e vapor.

!Jm aE l

Figura 7 .

Arreglo d e l a s t u b e r i a s d e aqua c a l i e n t e e n C . P .

I.

0'

CERRO

PRIETO

/

1

4

/

/

'

/

/

/'

pi

Figura 8 .

/

/ 0

I n c i d e n c i a de i n c r u s t a c i d n observada e n t u b e r i a s de aqua separada d e C.P. I. (Informe IIE, 1981)

t-

I

(IO'#)

-------

I

Figura 9.

I

I -

Distribuci6n de la incrustaci6n despositada en la tuberia de aqua separada del p z o M-91. (Informe IIE, 1981)

@ Figura 10.

a).-SOPOrmg QUIA00 Y L B R E (1979)

T i p s de soportes empleados para tuberias de aqua separada.

0

T- 400 0

E-?

0

Y

0

IC 4

Figura 1 1 .

Tuberias d e conducci6n d e mezcla

0

Y-m

WH 0

0

Y-I8

Figura 12.

Tuberia d e conducci6n de gases incondensables.

4

--____ a ) SEPARAW TlPO"WEBRE" bl SEIWRADOR CON TANQUE TANQUE DE A G W INTEGRAW DE AGUA EXTERN0 (UNIDAD 5 ) . (UNIDADES 1,2,3 Y 4 ) .

d ) SEPARADOR HORIZONTAL (ADAPTABLE EN LA TUBERIA)

91 SILENCIADOR ORIQINAL

Figura 13.

01

Cl SEPARADOR TIP0 HORIZONTAL

(EXPERIMENTAL)

ELIMINADOR DE HUMEDAD f l ELIMINADOR DE HfMEDAD " CENTRlFlX (UNIDAD 5 ) (UNIDAMS 1 , 2 , 3 Y 4 )

h l SILENCIADOR ACTUAL

E q u i p principal utilizado en el manejo de fluidos geot6rmicos en c.P. I.

I

Contra-

I3

2 3

Arm d. valwtas

I4

m

Soorada

LI8o~Cruo)ura 5 lmdleador 4. nwd 6 Toma d8 m u u t f a d. vapQ T D..coqa do vaaw 8 Vahulo do alivla 9 bbtvuta o a f i r x a 10 &a C orifloo II bblvula d o em. 12 Ramal pnreipat 4

K

I?

m a P 21

22 23

~~

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THE HGP-A GENERATOR FACILITY RESERVOIR CHARACTERISTICS AND OPERATING HISTORY EPRI Research Project 1195-12 Donald Thomas Hawaii I n s t i t u t e of Geophysics University o f Hawaii a t Manoa 2525 Correa Road Honolulu, Hawaii 96822, (808)948-6482 The HGP-A Geothermal Wellhead Generator F a c i l i t y , located on the Lower East R i f t Zone of Kilauea Volcano, was i n s t a l l e d as a p i l o t p r o j e c t t o demonstrate the technical f e a s i b i l i t y o f producing e l e c t r i c a l power from the geothermal r e s e r v o i r discovered by the HGP-A research w e l l i n 1976. The elect r i c a l generation f a c i l i t y was i n s t a l l e d i n June, 1981 and, a f t e r a number of i n i t i a l s t a r t u p problems, began commercial operat i o n i n March 1982; i t has now been i n operation f o r nearly 40 months. During t h i s period a number o f changes have occurred i n t h e w e l l f l u i d chemistry t h a t have yielded i n s i g h t i n t o the character o f the geothermal r e s e r v o i r associated with the East R i f t Zone and have i d e n t i f i e d a number o f p o t e n t i a l operating problems, f o r f u t u r e geothermal f a c i l i t i e s t h a t may be i n s t a l l e d on t h i s reservoir. WELL PRODUCTION AND CHEMISTRY DATE During i n i t i a l testing, the HGP-A w e l l was found t o be capable o f producing approximately 50 tonnes per hour o f a mixed phase f l u i d c o n s i s t i n g of approximately 22 tonnes per hour o f steam and 28 tonnes per hour o f l i q u i d a t a pressure o f approximately 1200 kPaa. Subsequent t o the i n s t a l l a t i o n and s t a r t u p o f the generator f a c i l i t y , t h e w e l l production rate, as i n d i c a t e d by the net declined by output o f t h e generator, approximately 3% per year during the f i r s t thirty-six months o f operation. This production decline occurred even w i t h the reduction o f t h e wellhead pressure 'from 1200 kPaa t o approximately 960 kPaa. However, during the t h i r t y - s i x t h month o f operation the w e l l production, and power p l a n t output, recovered t o a l e v e l s l i g h t l y above the maximum production r a t e encountered during t h e f i r s t months o f operation. This l e v e l o f production has undergone a s l i g h t decline since t h i s increase, but a t a r a t e not s u b s t a n t i a l l y d i f f e r e n t from t h a t occurring p r i o r t o the production increase. The f l u i d chemistry encountered during t h e i n i t i a l production t e s t s o f HGP-A showed a low t o moderate dissolved s o l i d s content o f

mg/kg consisting approximately 2,000-3,000 predominantly o f sodium c h l o r i d e and dissolved s i l i c a accompanied by lesser amounts o f potassium and calcium. The major dissolved gases consisted o f carbon dioxide, hydrogen s u l f i d e , n i t r o g e n and hydrogen. Subsequent t e s t i n g found an increasing t r e n d i n t h e major dissolved i o n concent r a t i o n s but a r e l a t i v e l y stable s i l i c a concentration. These trends have continued during the operational h i s t o r y o f the power p l a n t and, currently, t h e dissolved s o l i d s concentrations are approaching 20,000 mg/kg; silica concentrations have, however, continued t o maintain a r e l a t i v e l y stable concentration i n the production f l u i d .

I n contrast t o the dissolved solids, the gas concentrations i n the separate steam have remained r e l a t i v e l y constant experiencing a decline o f approximately 10% duri n g the production h i s t o r y o f the well. INTERPRETATION The changes i n the f l u i d production rate, although n o t i n o r d i n a n t l y large, were cause for concern w i t h regard t o the long-term p r o d u c t i v i t y o f t h e reservoir. However, the increase i n the production r a t e suggests t h a t t h e three-year decline was not the r e s u l t o f r e s e r v o i r depletion. Investi g a t i o n o f t h e production increase found t h a t 1) the wellhead pressure changes associated w i t h power increase occurred over a very short time period (on the order of minutes), 2) no geologic events (e.g. nearby earthquakes) accompanied the change i n production rate, and :I1 there were no detectable changes i n f l u i d chemistry coinc i d e n t w i t h t h e increase. On the basis o f these findings, we have concluded t h a t the decline i n production r a t e may have been the r e s u l t o f scale deposition i n the w e l l bore t h a t , due t o t h e h i g h r e s e r v o i r pressures, broke free and allowed flow rates t o increase from the deep production aquifers i n the well. This conclusion also suggests t h a t production from t h e HGP-A w e l l i s casi n g l i m i t e d and t h a t a l a r g e r diameter w e l l bore would permit a higher production r a t e from t h i s reservoir.

The chemical data obtained f o r the HGP-A f l u i d s suggest a number of important i n t e r p r e t a t i o n s about the reservoir. The low s a l i n i t i e s o r i g i n a l l y encountered demons t r a t e t h a t the primary mode o f recharge t o t h i s system i s from the c i r c u l a t i o n o f meteoric recharge from shallow aquifers t o depth i n the reservoir. The proximity o f the w e l l t o the ocean (approximately 10 km) and the normally h i g h p e r m i a b i l i t y o f Hawaiian basalts also i n d i c a t e t h a t struct u r a l features associated with the i n t r u s i v e bodies i n the r i f t zone c o n t r o l hydrothermal c i r c u l a t i o n and flow w i t h i n t h e reservoir.

from a (presumably shallow) b r i n e aquifer and a deeper higher temperature dry steam zone. This model i s supported by geothermometer calculations, using the non-condensible gas chemistry data, t h a t show a temperature of a t l e a s t 35OOC and possibly as high as 3 8 0 O C i n the p o r t i o n o f the r e s e r v o i r supplying the steam phase. In addition, production t e s t s o f p r i v a t e l y owned w e l l s adjacent t o HGP-A have also reportedly produced dry steam. Hence, a dry steam r e s e r v o i r i s i n d i c a t e d t o e x i s t w i t h i n the area around the HGP-A w e l l and may extend over a broad area w i t h i n t h e East R i f t Zone Complex.

i n salinity The substantial increase c l e a r l y shows, however, t h a t seawater i s now i n t r u d i n g i n t o t h e p o r t i o n of t h e r e s e r v o i r tapped by HGP-A (Figure 1). Temperature calculations using the Na-K-Ca geothermometer (Fournier, 1981) i n d i c a t e t h a t the i n i t i a l equilibrium temperatures o f the b r i n e phase approached 305OC but t h a t t h e i n t r u d i n g seawater i s r e f l e c t i n g a gradually declining equilibrium temperature t h a t i s c u r r e n t l y approaching 250OC. The s i l i c a concentration i n t h e b r i n e phases, which can also be used t o c a l c u l a t e r e s e r v o i r temperatures, does not, however, show a decrease corresponding t o the Na-K-Ca temperature decline. The apparent c o n f l i c t between the two geothermometers i s interpreted t o be t h e r e s u l t o f d i f f e r i n g r a t e s o f e q u i l i b r a t i o n o f the respective dissolved species: whereas s i l i c a e q u i l i brates very r a p i d l y the Na-K-Ca thermometer approaches e q u i l i b r i u m with r e s e r v o i r temperatures much more slowly. Hence, the temperatures calculated from s i l i c a concent r a t i o n s may more accurately r e f l e c t reserv o i r temperatures i n t h e immediate v i c i n i t y o f the w e l l bore.

IWLICATIONS

I t i s a l s o o f note t h a t t h e changing concentrations o f the a l k a l a i ions present i n t h e b r i n e i n d i c a t e t h a t the seawater basalt reactions i n the r e s e r v o i r are occurring a t a gradually increasing water rock r a t i o . This trend i s apparent from the much more r a p i d r e l a t i v e increase i n calcium and magnesium i o n concentration over t h a t for potassium i n the geothermal f l u i d s (Figure 2) The changes occurring i n t h e dissolved s o l i d s content o f the b r i n e phase, when compared with t h e s t a b i l i t y o f the gas concentrations i n the steam phase, also suggest a very important conclusion: the marked contrast i n the trends i n d i c a t e t h a t a t l e a s t two independent production zones are supplying predominantly a steam phase and a b r i n e phase t o the w e l l bore. Hence, the HGP-A w e l l i s d e r i v i n g i t s production

The chemical changes observed a t the HGP-A f a c i l i t y and t h e i r i n t e r p r e t a t i o n s have a number of important i m p l i c a t i o n s both f o r t h e continued operation and maintenance o f the generator f a c i l i t y and f o r the f u t u r e commercial u t i l i z a t i o n o f t h i s reservoir. The i n t r u s i o n o f seawater i n t o the reserv o i r tapped by HGP-A i s o f major concern f o r the f u t u r e operation o f the HGP-A faci l i t y . The increased s a l i n i t y o f t h e geothermal b r i n e s has led t o a substantial acceleration i n the deposition r a t e o f s i l i c a scale i n the b r i n e handling system. Even though t h e concentration o f s i l i c a has remained r e l a t i v e l y stable, the increased concentration o f dissolved ions has l e d t o a change i n the polymerization k i n e t i c s o f s i l i c a and hence the deposition r a t e has increased by a factor of a t l e a s t f i v e since t h e beginning of operations a t t h e HGP-A f a c i l i t y . This increased r a t e o f s i l i c a deposition has generated by f a r t h e most frequent and most troublesome maintenance problems occurring a t the generator facility. These problems include the following ( r e f e r t o Figure 3): 1.

Freeze-up o f the wellhead wing values;

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S i l i c a deposition i n the f l a s h separa t o r vessel and plugging o f the b r i n e discharge l i n e a t the vortex breaker;

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Plugging o f sampling ports;

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Plugging of the atmospheric b r i n e f l a s h tank and percolation ponds. The procedures currently undertaken t o address these problems include:

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I n s t a l l a t i o n o f a redundant b r i n e disposal l i n e from the e x i t p o r t o f t h e flash separator through t h e separator l e v e l control;

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Monthly t o bimonthly maintenance o f the b r i n e disposal l i n e s ;

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Expansion o f t h e b r i n e percolation ponds from 100 m2 t o more than 1000 m2

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Treatment o f t h e b r i n e phase with a p r e c i p i t a t i n g agent and semi-annual t o annual cleanout of the sludge s e t t l i n g ponds.

Although the costs o f implementing these procedures have been r e l a t i v e l y high, whether they w i l l be required f o r f u t u r e geothermal f a c i l i t i e s w i l l depend upon the type o f production zone (discussed below) encountered by f u t u r e geothermal wells i n the East R i f t Reservoir. O f l e s s immediate concern t o t h e continued operation o f the f a c i l i t y i s the apparent decline i n the calculated Na-K-Ca geothermometer temperature. Although t h i s decline i m p l i e s t h a t t h e i n t r u d i n g f l u i d s were e q u i l i b r a t e d w i t h the r e s e r v o i r a t a lower temperature as discussed above, the r e l a t i v e l y slow r a t e a t which these i o n s achieve e q u i l i b r i u m w i t h t h e r e s e r v o i r suggests t h a t the calculated temperatures are not necessarily representative o f t h e water temperatures i n the immediate v i c i n i t y o f the w e l l bore. An apparent decline i n t h e s i l i c a concentrations i n the b r i n e would, however, herald an imminent decline i n production temperatures and hence c a r e f u l moni t o r i n g of t h i s dissolved species i s continuing.

Another aspect o f t h e water chemistry relevant t o the continued operation o f the generator f a c i l i t y i s the apparent increase i n water:rock ratios. Experimental studies have shown t h a t (Mottle, 1983 and r e f e r ences therein), a t very low water:rock r a t i o s , the f l u i d chemistry i s r e l a t i v e l y benign but a t r a t i o s approaching 50, the pH of the f l u i d phase can decline t o l e v e l s as Although the water:rock low as pH 2 . r a t i o s represented by t h e f l u i d chemistry are c u r r e n t l y w e l l below 50, a s i g n i f i c a n t decline i n pH has occurred during t h e opera t i n g h i s t o r y o f the power plant; i n i t i a l pH's during the s t a r t u p of t h e w e l l were t h e most recent pH approximately 7.4, measurements made c u r r e n t l y i n d i c a t e a pH 6.55. This change represents an of increase i n hydrogen i o n concentration by a

factor of nearly ten since the beginning o f operations. Although no s u b s t a n t i a l problems have yet been encountered as a r e s u l t of t h i s pH decline, continuing a c i d i f i c a t i o n o f t h e b r i n e phase could lead t o unavoidable and unacceptable corrosion o f t h e b r i n e handling system. The r a t e o f pH decline i s , however, c u r r e n t l y very low and, a t present, there is no evidence t o suggest t h a t corrosion r a t e s are increasing. However, the many unknowns about the evolution of seawater basalt systems i n general and the hydrothermal system on the East R i f t Zone i n p a r t i c u l a r suggests t h a t c a r e f u l monitoring of the f l u i d pH and chemistry i s advisable. The chemical composition of the non-condens i b l e gasses present i n the steam phase have also l e d t o technical operations problems. Although some corrosion and i r o n s u l f i d e scale deposition has occurred i n the steam p i p i n g and t u r b i n e i n t e r n a l s , the absence o f ammonia o r boron and e f f e c t i v e s t e a d b r i n e separation have l e d t o r e l a t i v e l y low scale deposition r a t e s i n the turbine. The major focus o f deposition has been on the t u r b i n e i n l e t nozzels and, even here, maintenance i s apparently required only on a biannual basis. Another s i g n i f i cant maintenance problem encountered has been f o u l i n g o f t h e steam metering system and hence w e l l flow data i s not generally reliable. The most troublesome problems, a r i s i n g from the high hydrogen s u l f i d e conc e n t r a t i o n i n the steam phase have been associated with maintaining a clean a i r environment f o r p l a n t equipment. Hydrogren s u l f i d e promoted corrosion has generated maintenance problems f o r p l a n t a i r compressors, e l e c t r o n i c sensors and relays and general corrosion o f s t e e l framing and equipment t h a t i s r o u t i n e l y exposed t o the elements. A l l e v i a t i o n of these problems w i l l r e q u i r e t h e insta1lat:ion o f a new and higher capacity a i r f i l t r a t i o n system. Although the presence of Iiigh s u l f i d e concentrations i n the steam phase have r e s u l t e d i n high operating costs f o r the hydrogen s u l f i d e abatement system required t o meet environmental and community standards, t h e costs are more t h e r e s u l t o f t h e economics of the p l a n t s i z e than o f any inherently d i f f i c u l t technical problems associated with the abatement process. It i s o f note here as well, t h a t the absence o f ammonia or boron i n the steam have proven t o be a s u b s t a n t i a l advantage w i t h regard t o abatement of H2S i n the condensate steam; p a r t i t i o n i n g o f the gasses i n the condenser strongly favor the gas phase and less than 1%o f the H2 remains with t h e condensate stream t h a t i s used f o r Hence, recharge t o the cooling tower.

there appear t o be few technical b a r r i e r s t o cost e f f e c t i v e removal o f H2 f r o m t h e non-condensible gas stream for larger f a c i l i t i e s t h a t may be i n s t a l l e d on t h i s resource i n the future. The most favorable, and possibly most important, f i n d i n g of the research undertaken a t the HGP-A f a c i l i t y i s t h e conclusion t h a t a dry steam production zone may be present i n the geothermal r e s e r v o i r associated w i t h the Kilauea East R i f t Zone. I f t h i s production zone proves t o extend t o t h e r e s e r v o i r as a whole, as has been suggested by the production of dry steam from other wells on the East R i f t Zone, i t may be possible t o circumvent a number o f t h e technical problems associated w i t h the production o f the b r i n e phase a t HGP-A. Exclusion of b r i n e aquifers i n f u t u r e wells would e n t i r e l y eliminate the s i l i c a deposition t h a t has created both f a c i l i t y maintenance and b r i n e disposal problems. The continued, near constant r a t e o f production from the HGP-A w e l l suggests t h a t sustained steam production from the r e s e r v o i r can occur without major depos i t i o n or r e s e r v o i r plugging problems.

ONGOING RESEARCH A number o f research programs are presently underway a t t h e HGP-A f a c i l i t y t h a t are attempting t o improve our s t a t e o f knowledge about the r e s e r v o i r and i n an e f f o r t t o address some o f the technical problems that have occurred a t the generator facility.

Monitoring o f t h e r e s e r v o i r f l u i d chemistry has been underway since the i n i t i a l startup o f the w e l l and w i l l be continued f o r the foreseeable future. Much o f the current i n t e r p r e t a t i o n o f t h e r e s e r v o i r has r e l i e d upon the chemical data obtained t o the present; f u t u r e e f f o r t s w i l l attempt t o expand the i n t e r p r e t a t i o n s t o a n t i c i p a t e d f l u i d recharge r a t e s and chemical v a r i a b i l i t i e s w i t h i n the d i f f e r e n t horizons i n the reservoir. E f f o r t s are also underway i n v e s t i g a t i n g the d e t a i l e d chemical e f f e c t s associated w i t h s i l i c a polymerization and deposition, and a l t e r n a t i v e methods o f removal or recovery o f s i l i c a from the b r i n e phase. Recent batch t e s t s using metal i o n a d d i t i o n and f r o t h f l o t a t i o n on a bench scale have shown t h a t removal o f up t o 80% o f t h e dissolved s i l i c a i s e a s i l y achievable. Future t e s t s o f t h i s method on a flow-through system are planned. Other studies are i n v e s t i g a t i n g the production o f steam from t h i s geothermal

reservoir. Analysis o f c u t t i n g s from seve r a l w e l l s i n the r i f t zone are underway i n an e f f o r t t o determine whether detectable chemical o r physical c h a r a c t e r i s t i c s can be found i n the i d e n t i f i e d steam zones t h a t w i l l allow d r i l l i n g engineers t o design w e l l completion and casing programs f o r f u t u r e wells t h a t w i l l optimize steam production and minimize b r i n e production. PROSPECTS FOR THE FUTURE The production c h a r a c t e r i s t i c s o f the HGP-A geothermal w e l l suggest t h a t an extensive and robust geothermal r e s e r v o i r i s associaThe t e d w i t h t h e Kilauea East R i f t Zone. f i r s t f o r t y months o f operation have been characterized by a number o f s t a r t u p o r "learning" problems but, t o date, no insurmountable technical b a r r i e r s t o the development o f e l e c t r i c a l power generation on t h i s r e s e r v o i r have been encountered. The operation o f the HGP-A Generator F a c i l i t y has most c l e a r l y demonstrated t h i s conc l u s i o n by being able t o maintain an a v a i l a b i l i t y f a c t o r approaching 95% i n s p i t e o f the f a c t t h a t i t was the f i r s t geothermal generator constructed i n Hawaii and one o f t h e f i r s t i n the world t o be buftlt i n an a c t i v e volcanic environment. REFERENCES Fournier, R. O., 1981, Application o f Water Chemistry t o Geothermal Systems, i n Geothermal Systems: P r i n c i p l e s and Case H i s t o r i e s . L Ryback and LJP Muffler eds. J. Wiley and Hans. pp. 109 144.

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M o t t l e , 1983, Metalianalts, a x i a l hot springs, and the s t r u c t u r e o f hydrothermal systems a t mid-ocean ridges, Geol, SOC. Ad. B u l l , V.94, p 161-180

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Figure 2 Changes in r e l a t i v e concentration of Ka Ca, and Mg ions i n t h e r e s e r v o i r f l u i d . *Corresponds t o HGP-A f l u i d chemistry: K r i c h points r e p r e s e n t e a r l y f l u i d compositions, l a t e r compositions trend toward higher Ca concentrations. Label points a r e a s follows: 21 = hydrothermal vent f l u i d s a t East P a c i f i c Rise; R = Reykjanes Peninsula (a seawater dominated geothermal system i n I c e l a n d ) ; G = submarine hydrothermal vent f l u i d s a t Galatagos I s l a n d s ; SW = unaltered seawater compositions. F i l l e d numbered points (except 21) represent equilibrium ion compositions found i n high temperature seawater: b a s a l t experiments. The number a t each point correspond t o t h e seawater: b a s a l t r a t i o .

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EFFECTS O F H I G H NONCONDENSlRLE GAS LOADS ON G E O T H E R M A L SURFACE CONDENSERS - A CASE STUDY b y M a r y R. M a t t e s o n a n d G r e g L . S t a r n e s P a c i f i c Gas a n d E l e c t r i c C o m p a n y 7 7 Beale S t r e e t San F r a n c i s c o , C a l i f o r n i a 94106

ABSTRACT The l a r g e c o n c e n t . r a t ion of noncondensible gases present in the g e o t h e r m a l steam f i e l d s a t The G e y s e r s complex o f power p l a n t s p o s e s u n i q u e problems t o condenser design. Proper v e n t i n g o f t h e s e gases from t h e condenser is c r i t i c a l t o provent poor condenser performance. This paper d e s c r i b e s t.ho t e s t i n g o f t h e i n t e r n a l g a s removal d e s i g n and t h e a s s o c i a t e d v e n t i n g equipment. o f t h e s u r f a c e c o n d e n s e r a t P a c i f i c Gas a n d E l e c t r i c C o m p a n y ' s G e y s e r s U n i t 15 P o w e r P l a n t . Findings i n d i c a t e t h a t t h e g a s e s are not bcing properly vented, resulting i n a l a r g e area o f gas b l a n k e t e d tubes. In this gas blanketed region, t h e h e a t t r a n s f e r is s e v e r e l y r e d u c e d s o t h a t thi.s t u b e s u r f a c e is no l o n g a r The f u n c t i o n i n g t o condense steam. ultimate r e s u l t of this gas blanketing is t o r e d u c e t h e p e r f o r m a n c e of t h e c o n d e n s e r below t h e l e v e l which would be expected i n the absence of t h i s high noncondensible gas load.

INTRODUCTION

T h e p o w e r c y c l e f o r I J n i t 15 o f P a c i f i c Geysers complex i s s h o w n s c h e m a t i c a l l y '1 n F i g u r e I.. S u p e r h e a t e d steam, w h i c h o c c u r s n a t u r a l l y i n t h e a r e a of N o r t h e r n C a l i f o r n i a known a s T h e G e y s e r s , 90 m i l e s n o r t h of San F r a n c i s c o , passes t h r o u g h t h e low p r e s s u r e t u r b i n e a n d i s e x h a u s t e d i n t o t h e steam s u r f a c e condenser. Steam-jet gas ejectors are u s e d t o remove t h e n o n c o n d e n s i b l e gases from t h e c o n d e n s e r a n d m a i n t a i n c o n d e n s e r vacuum. The g a s e s t h e n p a s s t h r o u g h t h e h y d r o g e n s u l f i d e !H2Sj abatement system where t h e 9 s is t r e a t e d t o meet a i r p o l l u t i o n c o n t r o l s t a n d a r d s . The steam c 0 n d e n s a t . e a n d c i r c u l a t i n g water a r e combined and pumped t o g e t h e r t o t.he c o o l i n g Lower. The c o o l e d water from t h e c o o l i n g

G a s and Electric's

t o w e r b a s i n i s t h e n r e t u r n e d as t h e c i r c u l a t i n g water s u p p l y t o t h e surface condenser. T h e steam s u r f a c e c o n f d e n s e r a t U n i t 15 w a s the fi.rst surface condenser At employed f o r g e o t h e r m a l s e r v i c e . 1:he t i m e t h a t t h e c o n d e n s e r was d e s i g n e d ( t h e u n i t w e n t on l i n e i n J u n e o f 1 9 7 9 ) , v e r y l i t t l e was known about designing an e f f e c t i v e gas removal s e c t i o n f o r t h e l a r g e concentration of noncondensible gases f o u n d i n The G e y s e r s steam f i e l d s . T h e I J n i t 15 c o n d e n s e r was o r i g i n a l l y d e s i g n e d f o r a l o a d of 0.4% by weight. n o n c o n d e n s i b l e s i n t h e main steam. T h e c o n c e n t r a t i o n a t s t a r t u p was 0 . 3 % . A t this level, the plant operated at i t s design output. However, t h e c o n c e n t r a t i o n has been i n c r e a s i n g s t e a d i l y O v e r s i n c e , t.o p r e s e n t l e v e l s Along o f a p p r o x i m a t e l y 0.6% - 0.75. w i t h t h i s i n c r e a s e , t.hr:re h a s b e e n a s t e a d y d e c l i n e i n t h e t o t a l steam a v a i l a b l e t.o t h e u n i t . T h e d e s i g n p l a n t steam f l o w a v a i l a b l e a t s t a r t u p w a s 1 , 1 3 1 , 7 0 0 lb./hr., w h i l e t h e c u r r e n t a v a i l a b l e s u p p l y is o n l y 7 0 0 , 0 0 0 l h . / h r . R e c a u s e of' t h e s e two r e a s o n s , t h e p e r f o r m a n c e of U n i t 15 h a s d e c l -ined. I n t h e n e a r f u t u r e , a t o t a l steam f l o w of 1 , 0 0 0 , 0 0 0 l b . / h r . may b e c o m e available for Unit 15. Thj-s s t e m is

expected to have a nonmndcmible gas percentage of 1.4%. Tests were'

performed t o p r e d i c t t h e performance of t h e condenser w i t h t h i s changed steam s u p p l y . T h e s e t e s t s were des i gn e d t o s t udy t h e c u r r e n t operation of the condenser a t reduced steam f l o w a s w e l l a s t o s t u d y simulated f u l l load conditions at the t o t a l e x p e c t e d steam f l o w r a t e . Particular attention was paid t o the g a s removal s y s t e m t o d e t e r m i n e i t s effectiveness.

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Generator

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Non Condcniiblc

Coaling Tower

Steam Turbine

Figure I .

Schematic of Geysers Unit 15 Power Cycle

CONDENSER 1)ESlGN

There were two reasons for suspecting that the gas removal system may be inadequate at the current. noncondensible gas concentration. First, the concentration of noncondensible gases in the steam supply has increased well above design levels. The second indication that the condenser gas removal design may not be providing for full venting of the noncondensible gases came from previous condenser performance tests. These tests showed that, at the increased noncondensible gas load, the condenser was performing below design. Substandard performance was reflected by a higher-than-design backpressure and terminal t.emperature difference and a lower-than-design heat transfer coefficient. Both internal and external inspections of the condenser tubes revealed minimal tube fouling. In addition, an on-line condenser tube cleaning system was recently installed at Unit 15 which further reduees internal tube fouling. Therefore, since tube fouling could not account, for this degradation in performance, inadequate venting of the noncondensible gases was suspected as a contributing factor. Inadequate venting would lead to gas blanketing of condenser tubes, a condit.ion where the noncondensible gases stagnate around thc tubes. Steam cannot reach these tubes, thereby reducing heat transfer severely and rendering this area thermally inactive.

The Unit 15 condenser consists of two identical tube bundles. Each tube bundle is a two-pass design. Figure 2 illustrates one of these bundles as i t was originally designed. There are 3665 tubes per pass supported by 1 3 support plates. Each bundle is open on a l l sides s o that the steam should flow as depicted in Figure 2, entering the bundle and flowing radially t.o the center gas removal area as i t condenses. The original design ot the gas removal section was based on a cascade design. The gas removal section consists of two "channels" cut out of the center of the tube sheets. These channels are separated by a vertical dividing platc which runs almost the entire length of the condenser. They are connected only on the return wat.er box end of the condenser. Along the length of these channels, baffle plates are mounted such that they a1 ternate with the tube support plates. These baffle p ates serve to force the gas and v a p o r flow nut int.o t h e inner tubes, where t is cooled and addit.iona1 moisture is removed.

Tm U-shaped ducts, shown as Item 10 in Figure 2 ( B ) , are used as support manbers i n the center of each tube support plate. One or t h e d u c t s I S mounted facing upward on top o f the

Horizontal section

C W Slde C W Sde

H W Side

Section bb’

Figure 2.

H W Slde

Section c c ’

( A ) Simplified c r o s s - s e c t i o n s of t h e o r i g i n a l design of one tube b u n d l e w i t . h i n t h e m a i n c o n d e n s e r o f U n i t 15. ( B ) S e c t i o n bb’ r e p r e s e n t s m o s t of t h e t u b e b u n d l e . (Ci Section cc’represents o n l y t h e p o r t i o n t h a t i n c l u d e s t.he vapor e x h a u s t h o o d . 1. S t e a m f r o m t u r b i u e . 2. Heat e x c h a n g e t u b e s . Only o n e - h a l f o f c o o l i n g water t u b e s shown i n e a c h s e c t i o n ; i n s e c t i o n s b b ’ a n d cc’ t h e y a p p e a r head-on. 3. Water b o x e s ; c o n n e c t e d t o tubes. 4. “ C o l d “ water f r o m c o o l i n g t o w e r . 5. Cooling water t u r n s a r o u n d i n water b o x . 6. “ H o t “ water t o c o o l i n g t o w e r . 7. T u b e s h e e t s ( t u b e support.^); t h e s e a r e p e r f o r a t e d steel plates. 8. Vapor b a f f l e p l a t e s . 9. ‘Design’ flow p.attern of r e s i d u a l vapor. 10. 11-shaped s u p p o r t m c m b e r . 11. Out l i n e of b a f f l e p l a t e s a n d o f o r i f i c e s in t u b e s h e e t s , i . e . , t h e cross-s e c t . i o n o f t h e ‘ v a p n r c h a n n e l ’ . 12. Condensate d e f l e c t o r plate. 13. Vapor e x h a u s t hood.

g a s r e m o v a l c h a n n e l s , whi l e t h o o t h e r i s m o u n t e d f a c i n g downward below t h e channels. A t t h e i n l e t w a t e r box end of t h e c o n d e n s e r , t h e t o p U-shaped duct c o n n e c t s t h e g a s removal channels t o t h e gas removal exhaust. The o r i g i n a l design g a s a n d v a p o r f l o w is i l l u s t r a t e d i n F i g u r e 3 . T h e o r e t i c a l l y , t h e g a s anti a s s o c i a t e d v a p o r would t r a v e l i n t h e c h a n n e l s a l o n g t h e h o t p a s s s i d e from t h e o u t l e t water box t o t h e r e t u r n water box. It would t h e n t u r n around and flow back a l o n g t h e c o l d p a s s s i d e t o t h e gas removal e x h a u s t a t t h e i n l e t water box end. Thus t h e f l o w would c a s c a d e i n a n d o u t of t h e b a f f l e s along the length of the condenser, i n a direction opposite t o the cooling water flow. From t h e r e s u l t s o f s t u d i e s c o n d u c t e d i n 1979, i t w a s c o n c l u d e d t h a t t h e H 2 S P a r t i t i o n i n g ' might b e improved by modifying t h e gas removal d e s i g n . M o d i f i c a t i o n s were m a d e t o t h e c o n d e n s e r i n 1980 as s h o w n i n F i g u r e 4. A p l a t e w a s welded along t h e upper tl-shaped d u c t t o c o n v e r t i t i n t o t h e gas removal c h a n n e l . Vent o p e n i n g s were c u t i n t o t h e b o t t . o m o f t h i s d u c t .

Design Vapor Flow

"Cold" Wafer Side

Figure 3.

"Hot" Water Side

Design vapor flow p a t t e r n .

T h e g a s a n d v a p o r f l o w was t h e n a b l e t o e n t e r t h e channel between each support p l a t e along the length of the condenser and be c a r r i e d t o t h e gas removal e x h a u s t , as i l l u s t r a t e d i n F i g u r e 5. These m o d i f i c a t i o n s essentially converted the cascade venting design into a distributed venting design. ' P a r t i t i o n i n g r e f e r s t.o t h e a m o u n t o f H2S w h i c h r e m a i n s i n a g a s e o u s s t a t e a n d is n o t d i s s o l v e d i n t h e c o n d e n s a t e during t h e condensing process. For e x a m p l e , a 70% p a r t i t i o n i n g l e v e l w o u l d i n d i c a t e t h a t 7 0 % o f t h e H2S r e m a i n s i n a g a s e o u s s t a t e w h i l e 30% i s dissolved i n t h e condensate. H2S i s a r e g u 1a t e d a i r p o 1 111t a n t . ; t h e r e f o L' e , PGPrE m u s t l i m i t t h e r e l e a s e o f H2S t o H2S i n t h e g a s e o u s t h e atmosphere. s t a t e is a b a t e d i n t h e S t r e t f o r d s y s t e m , w h e r e i t is c o n v e r t e d t o e l e m e n t a l s u l f u r and water. Any H z S d i s s o l v e d i n t h c c o n d e n s a t e must b e treated using a c o s t l y secondary fue necesaria para i n d i c a r que no es vdlido ponerle u n precio a1 vapor partiendo del petr6leo que se req u e r i r i a para producir, mediante quemado en una c a l d e r a , una cantidad s i m i l a r de vapor a esas condiciones de presi6n y temperatura. b ) La duraci6n de l a Central en operaci6n s e ha considerado de 20 aiios por l i m i t e de l a duracidn del equipo, mas no del yacimiento geotermi co. Es deci r , conservadoramente se

supone que a1 aiio 20 de operaci6n el equipo t i e n e u n v a l o r de r e s c a t e n u l o , aunque a1 yacimiento tendrd que quedarl e todavia algo de v i d a . Se p a r t e de l a base que a1 hacer el a n d l i s i s de comportamiento del yacimient o s e ha dejado una holgura s u f i c i e n t e para que sea c i e r t o l o anLerior. Esta premisa, tendrd mucha importancia a1 comparar mdquinas de d i f e r e n t e consumo u n i t ? r i o de vapor. En el a n d l i s i s , en todos 10s casos s e considerard que el yacimiento dura por l o menos 20 aiios. La experiencia de Ceivo P r i e t o e s t 5 demostrando que el equipo geotbrmico seleccionado con a c i e r t o puede dui-ar mds de 30 aiios, per0 aquf s e ha preferido mantener l a c i f r a anter i o r por conservadora. c ) Factor de planta. La experiencia en F;bxico indica que 0.88 es u n f a c t o r r e a l i s t a , s i n embargo, considerarenios 0.8 t a n t o para Cent r a l e s como para Plantas a Contrapresidn. Una c e n t r a l geot6rmic.a tiene un f a c t o r de planta mayor que e l cle una termoelbctrica, por que no t i e n e caldera n i condensadores con tubos, dos f a c t o r e s que afectan notablemente a l a s horas de t r a b a j o de una terno convencional Las plantas a contrapresidn, tedricamente tienen u n f a c t o r mds a1 t o , ya que no tienen m6s equipo que l a turbina y gg nerador, s i n embargo, e s t 0 no s e cumple porque hay muchos casos en 10s que el pozo quc alimenta l a planta no produce s u f i c i e n t e vapor para generar 10s 5 !IN ocasionando l o que en el a r g o t se denomina "derrateo". d ) Para hacer comparaciones econ6micas es conve n i e n t e mencionar dos t i p o s de campos geotbrmicos, tomando como base l a experiencia mexi cana. Campo Sedimentario ( t i p o Cerro P r i e t o r y Campo Volcdnico ( t i p o Los Azufres). Esta d i v i s i d n que pudiera parecer u n t a n t o a r b i t r a r i a e s l a m6s adecuada para agrupar 10s par6metros econdmicos mds relevantes. El p r i mer0 es u n campo donde todos 10s pozos que s e hacen son productoi*es, aunque u n c i e r t o porcentaje d e e l l o s f a l l a p o r causas mec6nicas durante l a perforacibn. Todos 10s pozos cuestan prikticamente l o mismo, su produccibn de vapor y agua es cercana a l a prome-d i o del campo, el contenido de gas en el vala por e s muy parecido de u n pozo a o t r o , perforacidn de pozos :,e puede programar tra? lapada con l a construccibn de l a Central y l a reparacidn y reposicidn de pozos es tamb i bn bas t a n t e predecibl e. En cuanto a1 Campo que hemos denominado Volcdnico, s e t i e n e que l a incertidumbre para predecir s i u n pozo en perforacidn saldrd productor o s e r 6 seco, o f a l l a r a por problemas mecdnicos e s muy grande. El costo de u n pozo a o t r o as7 como el contenido de gas var i a considerablemente. Hay que p e r f o r a r 10s pozos productores a n t e s de c o n s t r u i r l a cent r a l . La duracidn de 10s pozos es mayor que en e l cas0 a n t e r i o r y requieren de menos man tenimiento, debido a menores problemas de in crustaciones. Con l o que hasta l a fecha s e conoce dl. 10s

.

nuevos campos geot6rmicos en M6xicoysolaiwfi t e Cerro P r i e t o cae en l a c l a s i f i c a c i 6 n de sedimentario (sinbnimo de homog6neoypredecL b l e ) mientras que Los Azufres, Humeros y La Primavera caen en Volca’nicos (sin6nimo de heterogeneo, impredeci b l e , cada pozo u n caso). T h e s e bien en cuenta que en 10s campos volcbnicos d e Flexico l a presi6n atmosfg r i c a es del orden de 0.7 atm, ya que estbn a 2800 msnm. Toda e s t a descripciGn, de dos t i p o s de campos, va orientada a mostrar l o d i f e r e n t e que sera’n 10s resultados a1 e s t u d i a r uno u o t r o caso. Sin embargo, en e s t e a r t i c u l o l o que s e comparar6 sera‘ el us0 de Centrales y de Plantas a Contrapresidn en u n campo Volca‘nico solamente (ma’s precisamente, t i p 0 Los Azufres). e ) Cuantificaci6n en dinero de consumos a d i c i g nales. A1 comparar econ6micamente dos i n s t 5 1 aciones geotgrmicas habra’ que c u a n t i f i c a r 10s consurnos de a u x i l i a r e s , l a s pErdidas de c a l o r y l a eventual incapacidad de una cent r a l para generar l a potencia mzxima. El c r i t e r i o que s e a p l i c a , d i f e r e n t e a1 de termoel6ctricaY e s que una planta geot6rmica s e i n s t a l a en l a zona donde e x i s t e el rg curso y que s u potencia l a define prinieramente l a capacidad del yacimiento, l a que debe s e r razonablemente mayor a l a potencia a i n s t a l a r , y segunda, una c i e r t a normaliza ci6n en el tamaiio de l a s unidades de genera ci6n. Por l o t a n t o el consumo de a u x i l i a r e s el 6 c t r i c o s (energia el 6 c t r i ca que s e gener6 y no s e vendi6) a s ? como l a incapacidad de l a planta para d e s a r r o l l a r su potencia m a x i ma por alguna f a l l a en el disefio ( equipo que s e compr6 y que no genera l o p r e v i s t o ) , que son generalmente muy bajos en proporci6n a l a potencia generada, s e consideran como u n cargo por demanda en c e n t r a l mbs o t r o por demanda en pozos. En o t r o s pala-bras, en geotermia 1 KW de a u x i l i a r e s es equivalente a que l a planta genere 1 KW mcnos que l o p r e v i s t o a plena carga, y e s t o s e c a s t i g a con u n valor proporcional a1 c o s t o de l a planta completa, mbs l a p a r t e proporcional de pozos que debieron perforarse (conscmase o no vapor a d i c i o n a l ) . En cuanto a1 consumo de a u x i l i a r e s a vapor s610 s e l e s c a s t i g a por el incremento en p g zos (con su reparaci6n y reposici6n) para e n t r e g a r el vapor requerido. Para c a s t i g a r e l consumo de c a l o r adicional de una opcidn de p l a n t a , digamos p6rdidas de c a l o r en 10s vaporductos, s e supone que el vapor es siempre saturado p o r l o que l a p6rdidad de c a l o r s e traduce en condensaci6n y no en caida de temperatura. Aproxima damente condensar 1 Kg de vapor requiere una perdida de 500 Kcal. Es d e c i r , una p6rd i d a de 1 (Kcal/hora) s e penaliza con el de equivalente a producir 1/500 (Kg/hora) vapor adicional ya que el condensado no s e u t i l i z a , s e purga.

f ) Para el a n d l i s i s econ6rnico no incluiremos e l

costo f i n a n c i e r 0 del dinero que s e requiere para l a s inversiones. Esta s i m p l i f i c a c i 6 n en c a s i nada a f e c t a l a comparacidn econdmica que s e pretende, per0 debe s e r tomada en cuenta s i s e c a l c u l a el costo real del KWh generado para f i n e s de r 6 d i t o de l a inver-sidn. La comparaci6n s e hace a v a l o r presente considerando una t a s a de rendimiento o t a s a de descuento del 10%y que no hay escalaciones d i f e r e n c i a l e s e n t r e 10s d i f e r e n t e s productos que afectan a 10s costos. g) Los r i e s g o s , l a s ventajas y desventajas, el grado de integraci6n nacional, a s 7 como o t r o s f a c t o r e s que todavia no s e han cuantificado en dinero, no s e incluyen en l a cornpa raci6n econ6mica. S610 se indican c u a l i t a t i varnente y s i r v e n como apoyo s u b j e t i v o para l a decisi6n f i n a l . h ) Fletodol ogia. En u n cal endario de inversiones s e indican a precios de 1985 l a s erogaciones Los gastos permanentes t a l e s como operaci6n y mantenimiento s e distribuyen anualmente en el tiempo a precios constantes. Se pasan est a s cantidades a valor presente tomando como aRo cero el i n i c i o de generacidn de l a Cen-t r a l . El consumo de vapor a d i c i o n a l , consumo de a u x i l i a r e s , c a l o r p e r d i d o p o r hora e n l a s l i n e a s y o t r o s f a c t o r e s menores, s e calculan por separado. i ) Casos a comparar: Lo que s e pretende en e s t e e s t u d i o es comparar dos opciones de explotaci6n para u n rnismo campo geot6rmico. En conc r e t o tomaremos Los Azufres usando c e n t r a l e s de 110 MW o usando plantas a contrapresidn ( 2 2 de 5 M W ) . La comparaci6n es hasta c i e r t o punto hi pot6tica pretendiendo sol amelite s e r vir de base para i l u s t r a r e l mgtodo. La comparaci6n exacta d e e s t a s opciones es demasia do amplia como para comprimirla en e s t a s pbginas. COSTOS a ) Costo de pozos y vaporductos. Para comparar l a exolotaci6n de Los Azufres (donde l a ores i 6 n atmosf6rica es 0.73 bar) con c e n t r a i e s de 110 N W y plantas a contrapresi6n ( 2 2 de 5 FlW) s e considera l o s i g u i e n t e :

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Costo por pozo (precios 1985) Vapor por pozo productor - Proporci6n pozos productores: Fallidos - Consurno e s p e c i f i c o Central Planta a de vapor por llWH Contrapresi 6n Pozos para Central 110 Kid Pozos para 22 x 5 FilW Vaporductos Central - DuraciBn cada pozo Mantenimiento por pozo

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Costo mantenimiento

400 F1$ 60 T/H 1:l 9. C (T/M!H)* 12.0 (T/EWH) 33 pozos 44 pozos 800 I;$(**) 10 aiios 1 vez cada uno 40 M$ cada vez

Para i n c l u i r e s t o s v a l o r e s en e l a n d l i s i s econdmico s e r e n e c e s a r i o c a l e n d a r i z a r l a p e r f o r a c i d n y e l mantenimiento de cada o p c i d n y luego p a s a r l o a v a l o r presente.

*

I n c l u i d o vapor p e r d i d o p o r purgas en 10s vaporductos. (**) Tomado de J.L. Mora, Ref. 8

b) Costos de l a C e n t r a l y P l a n t a s a ContrapreTomando como base l o gastado en Cer r o P r i e t o y p o n i e n d o l o a p r e c i c s de 1985 se t i e n e para una C e n t r a l de 110 MW a p r o x i madamente l o s i g u i e n t e :

m.

-

-

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Turbogenerador y condensador T o r r e de e n f r i a m i e n t o Equipo I,iateriales mecdnico el6ctrico civil e x t e r i ores Servicios liano de obra I n g e n i e r i a y DiseRo Impuestos, derechos T o t a l (110

NW)

Costo u n i t a r i o d e l KCI i n s t a l a d o

4 300 I;$ 925 2 715 150 570 1 470 960 1 800 2 700 320 90 16 000

-

CALENDAR10 DE EROGACIONES. Para una c e n t r a l de 110 I1111 se r e q u i e r e n 33 E z o s de 400 F;$ cada uno. La c e n t r a l cuesta 16 000 E$, t a r d a 4 aRos l a c o n s t r u c c i d n y se paga 'aproximadamente 20% e l primero, 30% e l segundo, 30% el t e r c e r 0 y 20% e l cuarto.

E l c a l e n d a r i o de p e r f o r a c i d n es e l i n d i c a d o - e n l a p5gina s i g u i e n t e . Para 110 l:W producidos Icon 22 p l a n t a s de 5 r.iF se r e q u i e r e n 44 pozos pl2rforados a i g u a l r i t m o que para e l cas0 de una c e n t r a l , p e r 0 l a p l a n t a se paga y se i n s t a l a a1 t e r m i n a r s e cada pozo. La generacidn de e n e r g i a e l P c t r i c a se i n d i c a en GWh a1 aRo para cada cas0 y f i n a l m e n t e , usando una t a s a d e l 10% se c a l c u l a n l a s i n v e r s i o n e s , a p r e c i o s de 1985, en v a l o r p r e s e n t e a1 aRo cero. (Ver t a b l a s en l a pdgina s i g u i e n t e )

CGIIPARACIOK DE COSTOS. Costo de l a s i n v e r s i o n e s a p r e c i o s constantes de 1985.

145 000 $/KW

.

Para una p l a n t a a c o n t r a p r e s i d n de 5 FIW, tomando como base l a s i n s t a l a d a s en Los Azufres.

-

-

Turbogenerador Equipo Obra c i v i l llano de obra I n g e n i e r i a y DiseRo Derechos, impuestos T o t a l ( 5 ML;)

Costo u n i t a r i o p o r KW i n s t a l a d o

380 R$ 24 21 66 7 2 500 100 000 $/KW

c ) Operacidn y Mantenimiento. E l mantenimient o de 10s pozos i m p l i c a una r e p a r a c i d n p o r pozo a l a m i t a d de su v i d a , reponer 10s pozos a 10s 10 aiios de o p e r a c i d n y reemplazar completo e l vaporducto a1 d6cimo aRo de o p g racidn. Ademds, en l a c e n t r a l se r e q u i e r e una dotac i d n aproximada de 36 personas de o p e r a c i d n mds m a t e r i a l e s y equipo para sus f u n c i o n e s de o p e r a c i d n y mantenimiento. Para l a s p l a n t a s de 5 CW se r e q u i e r e n personas mds m a t e r i a l e s y equipo. Reparacidn de 1 pozo R e p o s i c i d n de 1 pozo Vaporducto

r:v

PLANTAS 5

Pozos Vaporductos P1 a n t a

- CEI!'i?P,L .- -_. . 123 000 $/Kli 7 OCO 145 000 $/KW

Totql iriversidn

275 000 $/KW

260 000 $/Kk

160 000;$/K'X 0 100 006 .$/KL;

1

Considerando ahora l a c o n t r i b u c i d n de cada conc e p t o a1 c o s t o d e l KkJh generado se t i e n e en $/KL:h a v a l o r p r e s e n t e con una t a s a de descuent o d e l l o % , usando e l c a l e n d a r i o i n d i c a d o a n t e r i ormen t e : CEIJTRAL Pozos P l a n t a y vaporductos Reposi c i d n pozos Reparacidn pozos 0 y Ii p l a n t a R e p o s i c i d n vaporductos

2.97

2.97

1.52 1.04 0.21 0.86

0.60 0. l:, 1.23

6.41 $/KKh

I'W

0

0.05 __.-

TOTAL

PLANTAS 5

3.1C

-.

6 . CO$/E;hh

16

En pesos de 1985 se c o n s i d e r a l o s i g u i e n t e :

-

Operacidn y mantenimi1:nto C e n t r a l 950 !$/aiio P l a n t a 5 !;W 370 K$/aRo

40

El$

400 EO0

t:$ i:$

Es n o t a b l e que aunque l a s p l a n t a s a c o n t r a p r e s i d n de 5 l;W u t i 1 i z a n m5s pozos que una c e n t r a l , e l c o s t o d e l KlJh p o r pozos es menor. Est0 se d e t e a c u e 1 a generacidn comienza a1 poco tiempo de acabado e l pozi3,

C A L E N C A R I Z A C I O N PLANTAS CONTRAPRESION

C E 1.1 T R A L

0

POZOS

CENT. Y VAP.

No. 8 7 6 5 4 3 2 1 0

5 5 5 5 5 5 3

%

20 30 30 20

GENEFACIOR GWH

770

1 14 L5 16 17 18 19

i0

0 1 2 3 4 5 6 7 8 9

770

REPOSICION POZOS No.

0 Y F1 K$

950

8 7 6 5 4 3 2 1 0

PLANTAS No.

GENERACION GWH

5 70 140 210

280

1

420 560 700 770

14 15 16 17 18 19 20

700 630 560 49 0 350 210 70

1AO

- 6

REPOSICION POZOS No.

0Y M N$

REPARACION POZOS No.

370

- 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

17

19

REPARACION POZOS No.

POZOS No.

RO

950

20

5 4

370

INFLUENCIA DE LOS PARAMETROS PRINCIPALES.Para1a

d ) Incrementando e l p r e c i o de l a s p l a n t a s a se incrementa e l p r e c i o de KWh como sigue:

1 razocontrapresicn nables para 10s para'metros p r i n c i p a l e s , s i n em bargo l a v a r i a c i d n de e l l o s puede t e n e r una in f l u e n c i a i m p o r t a n t e en 10s costos

Incremento

0%

a ) Tasa de descuento. A1 u t i l i z a r o t r a s tasas de descuento se obt i e n e n 10s s i g u i e n t e s v a l o r e s para e l c o s t o d e l KWh generado. Tasa

Central

C o n t r a p r e s i 6n

8% 10% 12%

7.22 8.41 9.47

6.02 6.60 7.23

10% 20% 30%

e ) Variando l a v i d a u ' t i l d e l y a c i m i e n t o , y suponiendo que no hay v a l o r de r e s c a t e d e l equipo, para l a s p l a n t a s a c o n t r a p r e s i d n se t i ene

8% Pozos P1a n t a Reposi cidn pc

-

2.43 2.50 0.88

Central 10% 12%

3.18 2.97 0.85

C o n t r a p r e s i Bn E% 10% 1 2 % 1

2.52 1.35 1.08

3.76 3.48 0.82

2.97 1.52 1.04

3.47 1.70 0.99

20s

Repara- 0.18 cidn p g 20s 0 y M 1.23 planta - - . TOTAL

0.18

0.18

0.21

0.21

0.21

1.23

1.23

0.86

0.86

0.66

- - -

7.22

8.41

9.47

6.02

6.60

CentrajPozos

P1 a n t a Reposicidn pozos ReparaciBn pozos ,O y M p l a n t a TOTAL

.

Contrapresi6n

2,6& 2.97 0.85 0.18 1.23

2.99 1.53 1.1E 0.26 0.61

7.91

6.57

f ) P e r f o r a n d o l a t o t a l i d a d de 10s pozos y l u e g o una veL t e r m i n c t u s i n s t a l a c )U sea una c e n t r a l o p l a n t a s a c o n t r a p r e s i 6 n $/KWh que e n t r e n en o p e r a c i d n en l a misma fecha se t i e n e : Central Pozos P1a n t a ReposiciBn pozos ReparaciBn pozos 0 y FI p l a n t a Reempl azo vaporductos

7.23

b ) Cambio de c a l e n d a r i z a c i d n . P a r t i e n d o de l a base que en e s t e momento hub i e r a 33 pozos perforados se compara l a o p c i d n de C e n t r a l c o n t r a p l a n t a s a c o n t r a p r e s i d n . Par a l a C e n t r a l se comienza de inmediato l a cons t r u c c i d n m i e n t r a s que para l a s de c o n t r a p r e s i z n se p e r f o r a n ademds o t r o s 11 POZOS. As7 l a s cosas, e l KWh queda a

Total

& T/tl 9 T/H 10 T/H

8.02 $/KWh 8.41 $/KWh 8.63 $/KWh

Contrapresidn

12 T/H 1 4 T/tl 1 6 T/H

6.60 $/KWh 7.09 $/KWh 7.88 $/KWh

2.95 2.97 0.CO 0.18 1.23 0.05

C o n t r a p r e s i Bn

4.23 1.95 1.39 0.27 0.88

----

-8.18

6.63 ;/Kwh

E s t e cas0 se asemeja un poco a Tejamaniles con l a d i f e r e n c i a i m p o r t a n t e que para d i c h o p r o y e s t o e l c o s t o d e l equipo s e r 6 mucho menor que e l que a q u i se i n d i c a . g ) Para e v i t a r una a l u s i 6 n d i r e c t a a1 cas3 de l a p l a n t a Tejamaniles de 50 F'I-J en Los A m - f r e s se ha hecho todo e s t e p l a n t e a m i e n t o so b r e una base h i p o t e t i c a de 110 IN. En e l c& so de Tejamaniles e x i s t e n o t r o s f a c t o r e s que h i c i e r o n mas recomendable l a i n s t a l a - - c i d n de una c e n t r d l de 50 MW que 10 p l a n t a s de 5 HW a c o n t r a p r e s i B n . IHPONDERABLES. A1 tomar una d e c i s i d n para e l g g i r l a o p c i d n mds adecuada habr8 que d a r d e b 1 do peso a 10s s i g u i e n t e s aspectos que no han s i d o c u a n t i f i c a d o s en ,dinero:

-

c ) Variando e l consumo u n i t a r i o de vapor Central

6.60 $/Kk;h 8.02 $/KWh

DuraciBn 20 aiios DuraciBn 10 aiios

La i n c i d e n c i a de e s t a t a s a en cada concept0 que compone e l KWh es Tasa

$/Kwh 6.60 6.76 6.91 7.06

-

-

Grado de i n t e g r a c i d n n a c i o n a l en l a f a b r i c 6 c i 6 n d e l equipo puede s e r cercano a1 80% en plantas a contrapresidn. La c o n f i a b i l i d a d de un sistema compuesto por 22 p l a n t a s de 5 MW es mayor que l a de una c e n t r a l de 110 NW. Una f a l l a p o r mal funcionamiento de alguna p r o t e c c i d n o f a l l a de o p e r a c i d n es ma's cost o s a en c e n t r a l e s de 110 KW. Una f a l l a en l a est:imacidn d e l c o n t e n i d o de gases en e l vapor, o su v a r i a c i d n en e l

tiempo a f e c t a a una c e n t r a l .

- Una planta chica s i r v e para exploraci6n del yacimiento a1 mismo tiempo que genera energia e l e c t r i c a . - En casos de topografia muy accidentada es p r e f e r i bl e evi t a r l a s conducciones de vapor y usar plantas a boca de pozo. - En cas0 de a b a t i r s e l a presidn de yacimien-tos a n t e s de l o p r e v i s t o , a l a s plantas pequeRas s e l e s puede q u i t a r l a primera rueda de Zlabes y operarlas a menor presi6n manteniendo l a misma potencia per0 bajando su e f i ci enci a. - Puede s e r determinante en e l a n a l i s i s l a s i tuaci6n en que no s e logren combinar adecuadamente 10s pozos para generar exactamente 5 M W y haya que " d e r r a t e a r " l a s unidades. En e s t e estudio s e ha aplicado u n c r i t e r i o netamente comercial para l a geotermia. Si por us0 de plantas masineficientes s e agota el y a c l miento a n t e s de tiempo, e s e f a l t a n t e de ener-gia habra que producirlo con o t r o s nedios que podrian a f e c t a r l a economia del proyecto COMCLUSIONES. Se han planteado l a s bases que deben considerarse para hacer una comparaci6n econ6mica d e opciones para el aprovechamiento de la energia geot6rmica. Se ha establecido una metodologia para r e a l i z a r l a comparaci6n de dos opciones. Utilizando valores de l o que ha costado l a Cell t r a l de Cerro P r i e t o y l a s Plantas a Contrapre si6n de Los Azufres s e ha hecho una comparacizq econ6mica para Los Azufres, llegdndose a que s i s e h i c i e r a n 10s pozos segiin el calendario supuesto s e r i a mds econdmico usar plantas a contrapresi6n. Para e v i t a r alusi6n di r e c t a a1 proyecto de Tejamaniles en Los Azufres el anal i s i s se r e a l i z 6 sobre bases h i p o t e t i c a s de una c e n t r a l de 110 MW contra 22 plantas de 5

del vapor y l a generaci6n de r l e c t r i c i d a d , el us0 d e plantas b a r a t a s , a contrapresibn, que pueden cornenzar a generar a1 poco tiempo de perforado el pozo, es sumamente a t r a c t i v o y v a l e l a pena e s t u d i a r l o a fondo en cada proyecto.

REFEREWAS. 1. HERNANDEZ DE L A TORRE, E. (1984). "Costos

a precios de 1984 de c e n t r a l e s geot6rmicas"

Informe ET-CP-OlE4. Depto. Fact. de Proy. C. F. E. 2. HIRIART, G. (196'5). "One year experience with portable back pressure t u r b i n e s i n Los Azufres". Ninth Korkshop on Geothermal Keservoir Engineering. Stanford University C a l i f o r n i a , Cecember. 3. GIACCOPELLO, 1:. (1985) "Alternativas de e z plotacidn de campos geot6rmicos" Tesis. Universidad Hichoacana de San Nicolas de Hddalgo.

4. HIRIART, G. (1985) "Los Azufres Geothermal Development" B u l l e t i n of the Geothermal sources Council , January. Vol 14, No. 1.

.

Re

5. FlORAN, Ei.J. (1982) " A v a i l a b i l i t y Analysis: A guide t o e f f i c i e n t Energy use". PrenticeH a l l , Inc. 6. GIPPIPO, R. and FlARCILLE, D.F. (1984). "Exergy a n a l y s i s of Geothermal Power P1 ants". Geothermal Resources Counci 1 Annual Fleeting. Reno, Nevada. August 1984. Transactions Vol. 8.

7. EiARSH, W. D. (1980). "Economi cs o f e l e c t r i c u t i l i t y power generation". Oxford Univers i t y Press (Engineering science s e r i e s ) .

FIW.

Se examine l a s e n s i b i l i d a d del precio de l a energia generada a n t e variaciones en t a s a de descuento, consumo e s p e c i f i c o de vapor y vida del yacimiento. Se han indiczdo 10s aspectos imponderables que deben tornarse en cuenta en l a comparacibn, per0 que toddvia no s e han cuantificado en dinero. Las v e n t a j a s econdmicasque aqui s e han indicado para l a s plantas a contrapresi6n desapare-cen cuando el que r e a l i z a el proceso para gene r a r y vender energia e l e c t r i c a , compra el va-por a u n t e r c e r 0 a u n precio f i j o , ya que tant o 10s imponderables como 10s ahorros por gene rar en cuanto s e perfora el pozo vienen i n c I u 1 dos en el precio del vapor. Es evidente en est e cas0 que convendria usar u n equipo e f i c i e n t e aunque sea d s caro.

La conclusi6n a l a que s e l l e g a es que a1 c o ~ s i d e r a r como u n s o l o proyecto l a producci6n

8 . FIORA, J.L.

(1984). "Costo estimado a1 reub i c a r l a c e n t r a l Tejamaniles a u n kilbme-t r o de d i s t a n c i a ( a n b l i s i s vaporductos)". Informe AP-TJ-0184. Depto. Fact. de Proy. C. F. E.

START-UP AND TESTING OF THE HEBER BINARY PLANT

AN UPDATE

Neil G. Solomon, Richard F. Allen San Diego Gas & Electric 101 Ash Street San Diego, CA 92112 (619) 235-7747

INTRODUCTION The purpose of the Heber Binary Project is to design, construct, and demonstrate a nominal 65MW (gross) geothermal power plant utilizing the binary cycle to prove the technical, economic, and environmental viability of binary cycle geothermal power generation. The availability of binary cycle technology on a commercial scale of will permit the future development moderate-temperature (below 400°F) geothermal reservoirs, which represent about 80% of the geothermal resources in the United States. SDG&E has developed Start-up and Testing Plans which will result in accurate and reliable plant and equipment performance data and accomplish the following Project objectives: o

Determine the operational and performance characteristics of the Heber Binary Power Plant, its equipment, and the geothermal reservoir over a wide range of conditions.

o

Develop data bases for plant, equipment, and materials performance over the entire demonstration phase of the Project.

o

Confirm operation of plant systems and components in accordance with design criteria.

o

Determine the optimum operating conditions for this plant and gather design information for improvement in designs for future plants.

This paper will present an update on the current status of systems start-up and testing at the plant and discuss the upcoming planned testing activities. START-UP STATUS The SDG&E Start-up Group began control verification and functional checkout of plant systems and equipment in October 1984, as construction of each system was completed. A s of June 5, 1985, all but one system, the hydrocarbon system, have completed start-up. Half of those systems completed have been accepted by Plant Operations. The remaining half are now being reviewed and should be accepted shortly.

One of the first key milestones for the plant was the initial delivery of hydrocarbon that This began a occurred in early April 1985. sequence of events that culminated on May 2 1 with a major project milestone: the rolling of the turbine. The following is a description of the events leading to turbine roll: While tanker trucks were unloading hydrocarbon to the storage sphere, the hydrocarbon system piping was evacuated and purged with nitrogen. On April 17, with purging complete, the system was ready to safely accept hydrocarbon. Three days later the system was evacuated to 7.5 psia and hydrocarbon vapor was introduced into the system. On April 24, with hydrocarbon vapor pressure equalized throughout the system, the transfer of liquid hydrocarbon from storage was started. By April 26, the cold flow of hydrocarbon through heat exchanger train B had been established. While the cold flow of hydrocarbon was taking place, the brine system was filled with 160°F brine and recirculation through the heat exchangers was begun. At this time, the only pumps in operation were one brine return pump and one hydrocarbon condensate pump. On May 8, t h e first hot brine was accepted from the production island and system warm-up commenced. At the start, 300 gpm of brine from one free flowing (downhole pump not in operation) production well was introduced into the warm-up loop. Over the next several days, the brine flow was gradually increased until 2250 gpm of 350°F brine was entering the warm-up loop. This brine flow required that two downhole pumps be in operation. As the hydrocarbon temperature exiting the heat exchangers increased, a hydrocarbon booster pump was put in operation to produce the supercritical pressure required for the turbine roll. At the time of the first turbine roll, the hydrocarbon conditions at the exit of the heat exchanger train were 330°F and 590 psig with a flow of 5000 gpm. The actual brine flow through the heat exchangers required to produce these The roll of the conditions was 3050 gpm. turbine and subsequent increase in speed to

synchronous speed was achieved without any problems. Figure 1 is a snapshot of the controlled step increases in turbine speed from 0 to 3600 rpm.

CRP-196

PSlBSll 32nn

P 811 S t @ 8WLI

_.(....(

16B8

-

ann e nene

-I

RPM 24W

...I..."....I''.

I

on

saee31e

I

I

x LI

( . . . . ( . . . ( . _ . . ( ._ . ( . . . _ (

_..__

lllll

--.--__.___

,

I

uif

*~-al-,g-----------.~.

o

Hydrocarbon Condensers

o

Hydrocarbon Condensate and Booster Pumps

o

Turbine Knockout Drum

o

Brine Return Pumps

o

Brine Flow Control Valves

o

Hydrocarbon Flow Control Valves

o

Brine Bypass Valve

o

Turbine Multi-purpose and Control Valve

o

Turbine Bypass Valve

The plant cooling system was not included in the model because none of its components are actively involved in process control.

OUT %

noof

Turbine

smut

RPI PRETRP T SPEED TU splr PVlX

o

n

wi .------.-----'---'---------------.--------------,g,",1.1.

'*,--.---.

nsieeii s m o iueinE-cEn

o*,

n*n

I4.M

Figure I Since May 21, the turbine has been rolled several times with either heat exchanger train A or B in operation. It is anticipated, at the time of this writing, that turbine synchronization will occur without difficulty sometime in mid-June. CURRENT ACTIVITIES A dynamic simulation of the plant control system

developed using a micro computer was recently completed. The goal of this effort was to provide SDG&E start-up personnel with control element tuning constants, confirm the operating characteristics of the plant actuators and sensors, and to develop a model for predicting the control loop response to normal load change commands or upset conditions.

Controller tuning constants were evaluated by simulating the system response to demanded load changes at different load levels using a range of turbine ramping rates. Standard controls system analysis methods were used to determine if potential instabilities existed and transients were plotted to show the characteristic of the expected responses. Controller tuning constants were selected to provide the fastest and most stable response possible over the full range of turbine operation. These tuning constants were placed in the plant control system prior to synchronization t o help insure adequate process control and to serve as starting points for the fine tuning of the process which will follow. Figures 2 and 3 illustrate a typical response of the process model to a commanded load increase and decrease using the optimum tuning constants.

Dynamic Simulation

,

Tamperalure (I)

Pressurr (pri)

307.5 I

The model that was developed contains the following major plant control loops: o

Brine Flow Control

o

Hydrocarbon Flow Control

o

Turbine (Governor) Control

Also included in the control system model was the dense phase alarm and trip logic for protecting the turbine from operation with liquid hydrocarbon present. The plant components included in the model were as follows: o

Brine/Hydrocarbon Heat Exchangers

Time (rnin)

Figure 2

585

.

Dynamic Simulation

d

-

O-

40

60

80

100

o

Initial Testing

o

Long-Term Testing

o

Facility Acceptance Testing

o

Operational Testing

o

Endurance Testing

m

n 20

- . . .- .

Testing will be divided into the following five phases:

0

0

.

- .

PLANNED TESTING ACTIVITIES

toad (UW)

20

.

120

Time (min)

Figure 3 The first sixty minutes of the transient plotted on Figure 2 show the turbine inlet temperature and pressure during a load increase from 30MW to 70MW. The second sixty minutes then show the effect of a load decrease back to 30MW. In either case, deviations from the desired turbine throttle conditions (306'F and 578 psia) was minimal. Figure 3 illustrates the difference between the demanded load and the actual megawatts produced by the process. This difference is caused by a combination of the energy storage capability of the heat exchangers and components of the control system which retard load change to maintain turbine quality hydrocarbon vapor. Many different operating scenarios have already been simulated using this dynamic model. Transient responses as described above have been generated and studied, and the following conclusions have been drawn: o

The control system as designed can control all expected normal operations.

o

The

The overall Project Testing schedule is shown in Figure 4 . Formal testing will begin following turbine synchronization and continue throughout the Demonstration Period ending in early 1988. Actual testing is impacted by the brine delivery schedule shown in Figure 5 .

TESTSCHEDULE

INITIAL TESTINQ

PLANT OPERATIONAL TESTING

FACILITYACCEPTANCE TESTINQ

Turbine ramp rates up to five percent per minute can be handled by the control system.

o

The characteristics of the heat exchangers and turbine knockout drum dominate system response.

Immediately following turbine synchronization, a series of load pickup tests will be performed to verify these conclusions. As more brine flow becomes available and the plant can operate at higher power levels, these tests will be repeated and compared to the results anticipated by operating the simulation under the same conditions. Throughout the Testing program, the dynamic simulation will be refined as required and used as a means of predicting plant performance for comparison with actual test results.

I

I

LONWERM TESTIN0

ENDURANCE TEST

Figure 4

turbine pressure control override is critical for large load excursions at ramp rates exceeding four percent per minute.

o

1 i 1 1

BRINE DELIVERY SCHEDULE

1-

1086

Figisre 5

1981

1008

Initial brine delivery is scheduled to begin in April 1985 and step up to fifty percent of the One required flow for full power in May 1985. hundred percent brine flow is not reached until a January-to-May time window in 1986. As a result, a flexible testing schedule is required to encompass equipment and low load testing in 1985. Full load testing of the plant and turbine begins after full brine flow is achieved in early 1986.

o

Reduction of generator output from full load to at least 50% load and return to full load by operator-commanded inputs to the Central Control System.

o

Operation of the plant at full load for a continuous 24-hour period.

o

BrinelHydrocarbon Heat Exchangers

During the inital part of the Demontration Period, the bulk of the plant Operational Testing will be conducted. These tests will determine the steady state performance of the plant, as well as its responses to changes in control setting and upset conditions. This phase will also contain a series of tests whose goal is optimization of plant performance. Following the completion of Operational Testing, the final six months of the Demonstration Period will be occupied by an Endurance Test to simulate commercial operation of the plant by demonstrating the ability of the plant to stay on-line at full load for long periods of time.

o

Hydrocarbon Condensers

In parallel with the specific tests identified

o

Cooling Tower

o

Hydrocarbon Condensate Pumps

o

Hydrocarbon Booster Pumps

o

Main Cooling Water Pumps

o

Brine Return Pumps

Initial Testing will begin with equipment Performance Guarantee and Benchmark Tests. These tests will serve to insure compliance of the installed equipment with the contract specifications and provide a baseline for the measurement of long term equipment performance. With the exception of the turbinegenerator, all of the following initial equipment tests can be completed prior to full brine flow:

During the period when brine flow is increasing from fifty percent to full flow, some Operational Testing will be conducted at reduced loads. These tests will consist primarily of control system tests to determine the system responses to changes in commanded load. Once full brine flow is achieved, the Turbine-Generator Performance Guarantee Test will be performed. This test will complete the final required checkout of plant equipment. Shortly thereafter, the Facility Acceptance Test will be performed. The successful completion of this test is a DOE requirement for the commencement of the two-year Demonstration Period. Listed below are the criteria which will determine the successful completion of this test: o

Completion of start-up and turnover of all plant systems to the Plant Operations Group.

o

Completion of Initial Testing on all plant components.

o

Achievement of brine sustain full load.

o

Demonstration of a successful start-up of the process from a cold shutdown condition to full load.

o

Demonstration of a successful shutdown of the process from full load.

flow

sufficient

to

as part of Initial Testing and Operational Testing, data will be periodically gathered throughout the Demonstration Period under the Long-Term Testing program. Data will be collected on the reservoir performance, major equipment and materials performance, and overall plant performance. This periodic data collection will be one of the primary means for generating such performance parameters as heat exchanger and condenser fouling rates, reservoir temperature decline, and material corrosion rates.

SUMMARY Start-up activities at the plant began to wind down after the turbine roll was achieved on May 21, 1985. A state of the art dynamic simulation of the plant control system was developed to assist start-up, using a micro computer. The results of case studies indicated a stable responsive control system capable of handling all normal plant operations. Now, with turbine synchronization expected in early June, plant personnel are poised to begin the major effort of testing plant systems and components that will take the Project through demonstration to commercialization.

INGEN I E R IA DE I N S TALACI ONES

DE PLANTAS GEOTERMICAS

Ranulfo Gutigrrez Ramirez I n s t i t u t o de Investigaciones El6ctrica.s Divisi6n Estudios de Ingenieria

R E S U M E N

Se describen algunas actividades de l a Divisi6n de Estudios de Ingenieria d e l I n s t i t u t o de Investigaciones Elgctricas realizadas en colaboraci6n con l a Comisi6.n Federal de Electricidad para incrementar l a capacidad de generaci6n geotermoel&trica e x i s t e n t e en M&im.

Los proyectos descritos s e agrupan en l a s siguientes Ekeas:

. .

Desarrollo de Ingenierias b6sicas de plantas geotgrmicas. Realizaci6n de Ingenierzas de d e t a l l e de sistemas de manejo de fluidos geotGrmicos

.

.

Estudios te6rico-experimentales de equipos y sistemas para l a explotacidn adecuada de l a energza geot6rmica.

I N G E N I E R I A DE INSTALACIONES DE

PLANTAS GEOTERMICAS

Ranulfo G u t i g r r e z I n s t i t u t o de I n v e s t i g a c i o n e s Divisi6n Estudios de Dante 3 6 13590, Mgxico, RESUMEN Se presentan algunas de l a s p r i n c i p a l e s a c t i v i d a d e s d e s a r r o l l a d a s en e l I I E sobre l a implementaci6n y a p l i c a c i 6 n de l a t e c n o l o g i a n e c e s a r i a p a r a incrementar l a u t i l i z a c i 6 n de l a e n e r g i a geot6rmica en l a generaci6n de e l e c t r i cidad.

Cada campo geot6rmicO r e q u i e r e p a r a s u explotaci6n una s e r i e de e s t u d i o s te6ricos y experimentales que conduzcan a l a mejor u t i l i z a c i 6 n d e l r e c u r s o e n e r g 6 t i c o . Consideran do l a generaci6n de e l e c t r i c i d a d algunos de .los e s t u d i o s n e c e s a r i o s son: s e l e c c i 6 n d e l ciclo; e s t a b l e c e r condiciones de operaciGn, s e l e c c i 6 n d e l sistema de manejo y c o n t r o l de f l u i d o s geot d r m i c o s , e s t a b l e c e r m6todos de disefio de equipo, s e l e c c i 6 n de m a t e r i a l e s , e t c . todo l o c u a l ha s i d o , desde l a fundacidn d e l I I E , uno de 10s p r i n c i p a l e s t e m a s de e s t u d i o y d e s a r r o l l o . INTRODUCCION

En l a Divisi6n de Estudios de I n g e n i e r i a ( E I )

d e l I I E s e han d e s a r r o l l a d o , t a n t o en colaboracidn d i r e c t a con l a Comisi6n F e d e r a l de ElectrL cidad ( W E ) como en forma independiente, v a r i o s proyectos p a r a incrementar l a capacidad de g e n e r a c i d n geotermoel6ctrica en M6xico destacando 10s s i g u i e n t e s : I n g e n i e r i a b 6 s i c a de l a U-5 de Cerro P r i e t o I . P a r t i c i p a c i 6 n en l a i n g e n i e r i a b d s i c a de Cerro P r i e t o I1 y 111. I n g e n i e r i a d e t a l l a d a de l a P l a n t a de Evaporaci6n de l a U-5 de Cerro P r i e t o I .

Ramirez ElGctricas ( I I E ) Ingenieria D.F.

m s a r r o l l o a n a l i t i c o y v a l i d a c i 6 n experimental de mstodos de disefio. Estudio de t b c n i c a s p a r a e l c o n t r o l de l a con@ minaci6n . Bombeo de salmueras geotCrmicas. Pruebas de v d l v u l a s p a r a s e r v i c i o geot&rmi&. Estudios t e r m o d i n h i c o s de d i f e r e n t e s c i c l o s p a r a generaci6n de e l e c t r i c i d a d como e l b i n a r i o , uno o v a r i o s pasos de evaporaci6n, e t c . Estudios p a r a o t r a s a p l i c a c i o n e s de l a e n e r g i a geot6rmica como son r e f r i g e r a c i b n , c a l e f a c c i h , acuacultura, e t c . E s t a s e r i e de proyectos puede agruparse en t r e s

d r e a s que son: I n g e n i e r i a s b g s i c a s , e s t u d i o s te6rico-experimentales e i n g e n i e r i a s de d e t a l l e desglos6ndose a continuaci6n 10s e s t u d i o s que se r e a l i z a n e n cada caso. En las I n g e n i e r i a s b h s i c a s s e han d e s a r r o l l a d o 10s s i g u i e n t e s aspectos : Estudio de a l t e r n a t i v a s p a r a l a l o c a l i z a c i 6 n de l a p l a n t a y d e l equipo de evaporaci6n. Balances t6rmicos p r e l i m i n a r e s y determinaci6n de las p r e s i o n e s de operaci6n. Estudios p a r a s e l e c c i o n a r , e l sistema de condug ci6n de 10s f l u i d o s g e o t h m i c o s .

Anblisis de a l t e r n a t i v a s p a r a l a d i s p o s i c i 6 n d e l aqua desechada.

I n g e n i e r i a d e t a l l a d a d e l drea de pozos de Cerro P r i e t o I1 y 111.

E s p e c i f i c a c i o n e s b 6 s i c a s d e l equipo p r i n c i p a l (Turbina, generador, condensador y sistema de vacio)

P a r t i c i p a c i 6 n en l a s p l a n t a s a p i e de pozo de Los Azufres.

Para l a s i n g e n i e r i a s de d e t a l l e s e r e a l i z a n 10s siquientes trabajos:

Pruebas de 10s evaporadores de l a U-5 y de 10s de Cerro P r i e t o I1 y 111. Experimentacicin en F l u j o en dos Fases. En forma simultdnea y como apoyo a 10s proyect o s , se han d e s a r r o l l a d o o t r a s a c t i v i d a d e s cubriendo l a s s i g u i e n t e s hreas: Estudios de f l u j o s b i f d s i c o s . Estudios de lavado y p u r i f i c a c i 6 n de vapor. Diseiio de s i l e n c i a d o r e s de mezcla y de vapor. Diseiio mechnico. PO y t u b e r r a s .

AnLlisis de e s f u e r z o s en equi -

.

Diseiio conceptual d e l sistema de evaporaci6nr separaci6n y conducci6n d e l vapor a las t u r b i nas y d e l aqua desechada a 1 sistema de disposL ciSn f i n a l (evaporaci6n s o l a r o r e i n y e c c i 6 n ) . Disefio de proceso y m e c h i c o d e l equipo de s u p e r f i c i e , separadores, evaporadores, s i l e n c i a dores y secadores. E s p e c i f i c a c i o n e s d e l equipo de evaporaci6n. Arreglos de equipo. Diseiio de t u b e r i a s de aqua, vapor y mezcla incluyendo determinaci6n de d i h e t r o , m a t e r i a l e s a u t i l i z a r , a s i l a m i e n t o , r u t a s de t u b e r i a s , an&

l i s i s de esfuerzos, e s p e c i f i c a c i o n e s y l i s t a s de m a t e r i a l e s .

t i e n e n dos o tres d i f e r e n t e s pasos de evaporaci6n.

Seleccibn y e s p e c i f i c a c i b n de bombas p a r a manej a r aqua desechada.

Para e l disefio adecuado de l a s l i n e a s de f l u j o B i f s s i c o deben considerarse l a r e l a c i d n agua/ vapor, l a maqnitud de l a p6rdida de presi6n que a su vez depende d e l didmetro y e l t r a z o de l a t u b e r I a . E s importante que l a p6rdida t o t a l de presi6n no s e a grande y e v i t a r que se presenten patrones de f l u j o t i p o i n t e n n i t e n t e . como una : 1 quia para e l c d l c u l o d e l d i h e t r o de e s t a s neas se recomienda considerar una velocidad e : t r e 10 y 3 6 m / s .

Seleccidn y e s p e c i f i c a c i 6 n de l a instrumentacidn.

-

Disefio C i v i l . C h e n t a c i o n e s y disefio e s t r u c t u r a l para s o p o r t e de equipos y t u b e r i a s . Disefio El6ctrico.Sistema de t i e r r a s , s u m i n i s t r o de energfa a motores e instrumentos y ma de alumbrado.

siste

En l o r e l a t i v o a 10s e s t u d i o s te6rico-experimen t a l e s l a s a c t i v i d a d e s son muy d i v e r s a s y van desde e s t u d i o s b i b l i o g r 6 f i c o s h a s t a e l desarro110 de pruebas y a n c l i s i s de r e s u l t a d o s de l a s mismas, todo e l l o orientado a v a l i d a r y mejorar 10s metodos de diseiio de e q u i p y t u b e r i a s . Lo a n t e r i o r se ha id0 integrand0 e n un manual de disefio mec6nico y de proceso de equipo qeot6rmL co de s u p e r f i c i e a s 1 como en programas de cdmpx t o para e l c6lculo de t u b e r i a s que manejan f l u J O bifdsico. A continuaci6n se d e s c r i b i r g n 10s d i f e r e n t e s

sistemas d e l &ea de p z o s que forman p a r t e de l a u t i l i z a c i b n de la enerqia q e o t 6 m i c a para 9% nerar electricidad. SISTEMAS DE EVAPORACION Y CONDUCCION DE FLUIDOS GEOTERMICOS. Debido a que en M6xico e x i s t e n b’asicamente campos qeot6rmicus de aqua dominant e 10s sistemas a d e s c r i b i r , incluyendo alqunas de l a s consideraciones y p a r h e t r o s empleados para e l disefio de sus componentes, son 10s siquientes: Sistema de manejo de mezcla.

En e l I I E se t i e n e e l programa de c6mputo FLUDOF capaz de d h e n s i o n a r autom6ticamente neas para f l u j o b i f g s i c o dando r e s u l t a d o s a c e p t a b l e s l o cual ha s i d o v e r i f i c a d o en algunas l f n e a s diseiiadas con este programa.

1g

.-

E s t e si? Sistema de evaporaci6n-separacibn tema e s t a c o n s t i t u i d o por 10s equipos i n s t a l a ya sea en la platafonna de cada pozo o en una p l a n t a de evaporaci6n y que t i e n e n l a funci6n de producir s u f i c i e n t e vapor y con l a pureza n e c e s a r i a para alimentar a l a s t u r b i n a s .

De 10s diversos mecanismos que e x i s t e n para 1 0 g r a r l a separacidn liquido-vapor e l mds u t i l i zado en explotaciones geotermoel6ctricas e s e l que t i e n e como p r i n c i p i o de funcionamiento l a fuerza c e n t r i f u g a . Lo a n t e r i o r s e debe a que son equipos compactos, con b a j o costo i n i c i a l , e f i c i e n c i a de separacidn a l t a y bajos costos de opera&& y m a n t e n h i e n t o . E l t i p o de separador empleado e s e l c i c l d n t i p o Webre teniendo como p r i n c i p a l e s p a r h e t r o s de disefio l a s s i guientes v a r i a b l e s : velocidad de entrada de l a mezcla y velocidad de ascenso d e l vapor. La maqnitud de e s t a s v a r i a b l e s debe f i j a r s e de nera que s e obtenga una a l t a e f i c i e n c i a de separacidn y b a j a pgrdida de presidn recomendsndose que l a velocidad de entrada s e a de 25 a 40 m / s y l a de ascenso de 2.5 a 4 m / s . En e l I I E se dispone de un procedimiento de disefiode

ma

Sistema de evaporacibn-separaci6n. Sistema de conduccidn y c o n t r o l de vapor. Sistema de agua separada, E l disefio de 10s sistemas y equipos s e hace co” siderando una vida 6 t i l de 30 aiios y de acuerdo a l a s condiciones de operaci6n y las siguientes normas:

Recipientes a presibn: ASME B o i l e r & P r e s s u r e V e s s e l Code, S e c t i o n V I I I

Divisi6n 1. Tuberras y v6lvulas: A N S I B31.1 Power Piping. Bombas cdrcamo y canales: Hydraulic I n s t i t u t e Standards. Instrumentaci6n: I S A Standards f o r Instrumentation. Sistema de manejo de mezc1a.Este sistema est 6 formado bdsicamente por l a s t u b e r i a s que ducen l a mezcla desde e l cabezal de 10s pozos h a s t a e l equipo de separaci6n aunque, tambign forman p a r t e d e l sistema l a s l i n e a s que t r a n s portan e l aqua d e l separador a 1 evaporador o evaporadores secundario y t e r c i a r i o cuando s e

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e s t o s equipos en que s e consideran t o d a s l a s v a

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RESULTS OF FIELD TESTING OF PROCESS FOR REMOVING H2S BY CONDENSING AND RE-EVAPORATING GEOTHERMAL STEAM AT CERRO PRIETO RP 1197- 6

Raul Angulo, Luis Lam, J a v i e r Gonzalez, and Pablo Mulas I n s t i t u t o de Investigaciones Electricas [ E l e c t r i c a l Research I n s t i t u t e ] Calzada J u s t o S i e r r a y Herreros Sur 2098 - Altos Mexicali, Baja C a l i f o r n i a Norte, 02109, Mexico Tel. (656) 2-81-86 Evan E. Hughes E l e c t r i c a l Power Research I n s t i t u t e 3412 Hillview Avenue Palo Alto, C a l i f o r n i a 94303 T e l . (415) 855-2179

This paper d e s c r i b e s t h e r e s u l t s of f i e l d t e s t i n g of a process f o r removing g a s s e s from geothermal steam, based on condensation and re-evaporation of t h e steam i n a shell-and-tube h e a t exchanger, upstream from t h e g e n e r a t o r .

The

gasses t h a t are removed a r e blown o f f with a small amount of t h e steam f e d i n the process, and t h e f i n a l product i s steam with a low c o n c e n t r a t i o n of H 2 S

a t a p r e s s u r e s l i g h t l y lower than t h a t of t h e i n i t i a l steam. 2’ The experimentation was c a r r i e d o u t with separated steam from well M-42

and CO

of t h e Cerro P r i e t o geothermal f i e l d . Los Geysers, C a l i f o r n i a , USA.

The equipment was p r e v i o u s l y t e s t e d a t

From January t o November 1984, more than 200

gas removal t e s t s were c a r r i e d o u t , f o r a t o t a l of 3 , 3 0 0 hours of o p e r a t i n g

time f o r t h e equipment.

A p r e s s u r e range from 60 t o 140 p s i g was covered,

and the gas content of the steam supply was varied.

The efficiency of removal

of H2S was, on the average, 93.5%, while that of C02 was 94%. The average value of the heat transfer coefficient was 673 BTU/h-foot*-'F

(3820 watt/m2-OC).

INTRODUCTION Evaluation work was completed on the process for removing H S by condensa2 tion and re-evaporation of geothermal steam, using separated steam from well M-42 of the Cerro Prieto geothermal field. The experimentation was carried out in the heat exchanger that was tested previously at Los Geysers, California (Ref. 1 and 2 ) , and reconditioned for the EPRI by Bechtel, which at the same time and u n d e r contract w i t h E P R I , prepared the test program (Ref. 3 ) .

The

Instituto de Investigaciones Electricas [Electrical Research Institute] carried out the field tests under a shared-cost contract with the Electrical Power Research Institute (EPRI).

The Cornision Federal de Electricidad [Federal

Electricity Commission] provided the geothermal fluid and collaborated in the installation of the steam separation equipment. The testing period was from January to November 1984; more than 200 field tests were carried out, for a total of 3,300 accumulated hours of operation of the equipment. The average efficiency of separation of H2S was 94% and the average value of the heat transfer coefficient was 678 BTU/h-foot2-'F(3820

watt/m2-'C).

This

paper gives the main results of the project.

AIM The aim of the project is to evaluate the functioning of the heat exchanger

during t h e p r o c e s s of s e p a r a t i n g H2S and C02 from geothermal steam, using s e p a r a t e d steam from well M-42 and varying t h e c o n d i t i o n s of p r e s s u r e , gas c o n c e n t r a t i o n i n t h e steam, and flow of steam which i s d i s c a r d e d t o g e t h e r with t h e separated gasses.

The process was evaluated by monitoring t h e following

parameters : a)

E f f i c i e n c y of removal of H2S

b)

E f f i c i e n c y o f removal of C02

c)

Heat t r a n s f e r c o e f f i c i e n t of t h e h e a t exchanger

d)

Net l o s s of energy These parameters were measured during a s e r i e s of f i e l d t e s t s i n which

t h e e f f e c t of t h e following independent v a r i a b l e s was determined: a)

Flow of steam discharged with t h e s e p a r a t e d g a s s e s , expressed as a percentage of t h e steam fed i n t o t h e system.

b)

Temperature d i f f e r e n c e between t h e i n s i d e and o u t s i d e of t h e t u b e s of t h e h e a t exchanger.

c)

P r e s s u r e of t h e raw steam.

d)

Gas c o n t e n t of t h e raw steam. The t e s t i n g program measured t h e e f f e c t o f each v a r i a b l e , w h i l e keeping

t h e other t h r e e constant.

I t a l s o measured t h e e f f e c t of r e c i r c u l a t i o n of t h e condensate on t h e e v a l u a t i o n parameters.

PROCESS The process begins with t h e production of steam, i n a double s e p a r a t i o n system f e d with water-steam mix from t h e head of well M-42.

The separated

steam e n t e r s on t h e s h e l l s i d e of t h e h e a t exchanger, where it condenses and most of t h e g a s s e p a r a t e s .

The-gas i s e x t r a c t e d from t h e h e a t e exchanger

t o g e t h e r with a p o r t i o n of t h e steam.

The condensate i s t r a n s f e r r e d t o a

s t o r a g e tank t h a t works a t a p r e s s u r e lower than t h a t of t h e s h e l l , so t h a t t h e r e w i l l be a temperature d i f f e r e n c e between t h e steam and t h e condensate, s i n c e t h e l a t t e r i s used as a cooling medium when it r e c i r c u l a t e s through t h e tubes.

Part of t h e r e c i r c u l a t e d condensate evaporates and produces steam

with a low gas c o n t e n t , but a t a lower p r e s s u r e than t h a t of t h e raw steam. Fig. 1 shows t h e equipment f o r t h e process, i n s t a l l e d a t t h e platform of of w e l l M-42. The specifications of the process

equipment, i t s o p e r a t i o n , c o n t r o l , and

methods of sampling and chemical a n a l y s i s are described i n Ref. 4 and 5.

The

e f f i c i e n c y of H2S was c a l c u l a t e d with t h e following formula: [H2S] c l e a n steam, ppm [H2S] raw steam, ppm

.RESULTS -

E f f i c i e n c y of gas removal.

I t was found t h a t t h e p r i n c i p a l v a r i a b l e s t h a t

a f f e c t t h e e f f i c i e n c y of gas removal are:

t h e q u a n t i t y of steam t h a t i s blown

o f f with t h e discharged g a s s e s (expressed as % of raw steam), t h e ammonia c o n t e n t

of t h e raw steam, and t h e p r e s s u r e of t h e steam when f e d t o t h e h e a t exchanger (Fig. 2 t o 7 ) .

Table 1 shows t h e e f f i c i e n c y of removal of H2S and C 0 2 a t t h e

t h r e e experimental p r e s s u r e s .

Table 1 EFFICIENCY OF GAS REMOVAL

(%I Maximum

Minimum

Average

H2S 60

97 97 96

115 140

94 88 86

95.4 94.4 92.6

92 89 91

94.1 94.2 94.0

c02 60

96 96 97

115 140

Heat transfer coefficient.

The heat transfer coefficient was correlated

with the principal variables (AT, pressure, % of steam b:Lown off, gas content of the blowoff) and no tendency was observed.

Fig. 8 is the graph of the heat

transfer coefficient vs. the % of steam blown off.

The average value of the

coefficient, for H2S removal tests, was 673 BTU/h-foot2-C) F(3820 watt/m 2-0 C ) , with a standard deviation of 15%. On completion of the testing period, the titanium tubes (0.030"

thick)

of the condenser-evaporator were replaced with stainless steel tubes (0.065"

thick) (Fig. 9 ) .

Various H2S removal tests were carried out, for the purpose

of calculating the heat transfer coefficient. Effect on production of electricity.

The principal factors contributing

to loss of energy in the H S removal system are the quantity of steam discharged 2

with the gasses separated from the raw steam, the pressure drop of the steam, and the quantity of water discharged by the system as a result of accumulation

i n t h e condensate s t o r a g e tank. of t h e condensate.

Energy i s a l s o consumed during r e c i r c u l a t i o n

The steam t h a t i s d i s c h a r g e with t h e separated g a s s e s

r e p r e s e n t s t h e g r e a t e s t l o s s of energy (which would be about 6 % ) , followed by t h e q u a n t i t y of water discharged by t h e system, which depends on t h e e f f i c i e n c y of t h e i n s u l a t i o n of t h e process equipment.

This energy l o s s should be compared

with t h e energy savings i n a g e n e r a t o r p l a n t when it i s supplied with r e l a t i v e l y c l e a n steam coming from a g a s removal system upstream from t h e t u r b i n e . Corrosion and i n c r u s t a t i o n s .

A f t e r completion of t h e f i e l d t e s t s , t h e

i n t e r i o r of t h e equipment was inspected and no i n d i c a t i o n of i n c r u s t a t i o n o r c o r r o s i o n was found.

I t was noted t h a t t h e h e a t t r a n s f e r c o e f f i c i e n t d i d not

change during t h e o p e r a t i n g t i m e of t h e equipment.

ACKNOWLEDGMENTS W e wish t o thank t h e Federal E l e c t r i c i t y Commission’s Cerro P r i e t o

Executive Coordinator f o r supplying t h e geothermal f l u i d from well M-42 f o r t h e t e s t i n g program.

We a r e a l s o g r a t e f u l f o r t h e r e s o l u t e support of a l l

t h o s e who a c t i v e l y p a r t i c i p a t e d i n t h i s p r o j e c t :

Hector Gamino, J a v i e r D i a z ,

Humberto Jimenez, Job Sanchez, and t h e personnel a t t h e E l e c t r i c a l Research I n s t i t u t e ’ s Chemical Laboratory a t Cerro P r i e t o . REFERENCES 1.

Coury and A s s o c i a t e s , I n c . Upstream H2S -removal from g e o t h e r m a l steam. E P R I AP-2100 F i n a l R e p o r t , November, 1981. 186 ppm.

2.

Hughes, Evan E. Upstream H2S removal. Sem i n a r i o EPRI/IIE s o b r e 10s programas d e Geg termia. J o i n t EPRI/IIE Geothermal Programs Seminar. Cuernavaca. M o r e l o s , Mgxico. Fe-b r e r o 22-25, 1982. p.45-48.

3.

Van d e r Mast, V i c t o r C . . Malcom C . Weekes and D a v i s P. McGrath. F i e l d T e s t of Geo--thermal upstream r e b o i l e r . Proceedings: S e v e n t h Annual Geothermal C o n f e r e n c e and -Workshop. San Diego. C a l i f o r n i a , J u n e 2830. 1983. EPRI AP-3271, pp. S e c t . 5-41-53.

4.

Angulo. R a G 1 , L u i s Lam and P a b l o M u l Q s . -C e r r o P r i e t o f i e l d t e s t of H2S removal by upstream r e b o i l i n g . Proceedings: Seventh Annual Geothermal C o n f e r e n c e and Workshop. San Diego, C a l i f o r n i a , J s n r 28-30, 1983. -EPRI AP-3271, p p . S e c t . 5-54-57.

5.

Angulo, RaG1, L u i s Lam and P a b l o MulSs. -C e r r o P r i e t o f i e l d t e s t of H2S removal by upstream r e b o i l i n g . Proceedings: Eighth Annual Geothermal C o n f e r e n c e and Workshop. S e a t t l e , Washington, J u n e 25-29, 1984. EPRI e - 3 6 8 6 , pp. S e c t . 5-7-12.

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DEMONSTRATION OF GEOTHERMAL SCALE CONTROL USING A FLASH CRYSTALLIZER RP1525-1 John R. Brugman and Douglas R. Brown The Ben Holt Co. 201 South Lake Avenue Pasadena, CA 91101 (213)684-2541 ABSTRACT One of the major impediments to further exploitation of the hydrothermal resource in western North America is the tendency of this fluid to deposit mineral scale in piping and equipment. As a part of EPRI's ongoing research program (RP1525) of scale control. techniques, a pilot scale (1/100) crystallizer test facility was designed and built. The test facility is a truck-transportable unit which is designed to operate on a wide variety of geothermal resources. The unit is self-contained and is not limited to operation at developed fields where offsite utilities are available. The facility is designed to perform proof-of-concept testing of two scale control techniques. The first is the flash-crystallizer-separator process developed by EPRI under RP1525-2. The second is brine stabilization by reheating. Currently, plans are being developed for operating the test facility at Cerro Prieto. The proposed testing will be conducted by the Instituto de Investigaciones Electricas (IIE) using the brine from well T-400 at Cerro Prieto 11.

DEMONSTRATION OF GEOTHERMAL SCALE CONTROL USING A FLASH CRYSTALLIZER RPl525-1 John R. Brugman and Douglas R. Brown The Ben Holt Co. 2 0 1 South Lake Avenue Pasadena, CA 91101 (213)684-2541 INTRODUCTION

Crystallizer

One of the major impediments to the further exploitation of the large hydrothermal resource in western North America is the tendency of this fluid to deposit mineral scale in piping and equipment. This is especially true of the hotter resources.

The heart of the test facility is the crystallizer vessel. The crystallizer is a standard draft-tube-baffle crystallizer which has been modified for geothermal service. It was designed and manufactured by Swenson. The vessel is 54" in diameter by 2 1 ft. long, constructed of carbon steel and rated for 450 psi at 500°F. Figure 2 is an outline sketch of the crystallizer.

EPRI has conducted a research program (RP1525) for several years with the objective of determining the feasibility of reducing geothermal power plant outage rates by 50 percent through the use of systematic scale control measures. The flash crystallizer concept is one candidate scale control technique. The conceptual design was developed during RP1525-2 by the Bechtel Group (Refs. 1, 2 h 3). As part of this work, a pilot scale test facility was designed and a crystallizer specification was developed. The test facility was designed to be 1/100th of the size of a It was also designed to commercial unit. accommodate brines from a variety of geothermal sites.

The crystallizer is equipped with three interchangeable draft tubes. As stated in a previous report (Ref. 3 1 , the internal recirculation rate is a key parameter in determining the rate of crystallization. The three draft tubes will be tested to determine which configuration promotes the best circulation in the vessel. Two of the draft tubes are straight-sided but of different diameters. The third is a converging-diverging venturi Fype draft tube. Since there is no practical way of directly measuring the internal circulation rate, the performance of the various draft tubes will be determined by measuring the degree of desaturation of scaling components in the brine that each draft tube causes.

CRYSTALLIZER TEST FACILITY Our objective under our current EPRI contract (RP1525-3) was to design and build a skid-mounted test facility suitable for proof-of-concept testing of the flash crystallizer process. In addition, we will provide engineering support during the field testing phase of the program.

In order to facilitate ease of replacement, each draft tube assembly consists of a draft tube and a baffle. The baffle is the same for each draft tube. The vessel is constructed so that the clarified brine can be withdrawn from any of four nozzles. This allows a means of testing the clarifier effectiveness by varying the rise rate and/or the clarifier residence time. Liquid samples can be taken of the fluid in the clarifier section and in the crystallizer section.

A process flow diagram of the test facility is shown in Figure 1. Although the stream parameters are for Cerro Prieto, the facility is designed to operate at a wide variety of geothermal sites. Any site where a flashed steam power plant could be built is suitable for the test facility. Figure 3 depicts the test facility fully erected during acceptance testing.

Clarif ier/Thickener The clarified brine is flashed to atmospheric pressure in a centrifugal separator and the liquid goes to the clarifier/thickener. The slurry that is

1

periodically withdrawn from the bottom of the crystallizer is also sent to the thickener. The clarifier/thickener serves to provide a concentrated slurry for recycle to the crystallizer if necessary. It will also be used to make up batches of seed material at the beginning of each test run. Any slurry not required for recirculation is pumped to the liquid waste line for disposal. Although the crystallizer is designed to relieve the supersaturation of scaling species at the operating conditions, the further flash to atmospheric pressure will re-establish the supersaturation and cause additional precipitation of scale. Therefore, the second function of the clarifierlthickener is to provide clarified brine for the brine reheat experiment. The clarifier is a pilot scale test clarifier manufactured by Denver Equipment Co. and is 36 inches in diameter and 3 feet high and is made of carbon steel. It has a conical bottom with a 113 hp adjustable rake mechanism.

Slurry Recycle Pump Concentrated slurry from the clarifier/ thickener will be injected into the crystallizer by a progressive cavity pump. The pump has: a chrome steel rotor and an EPDM stator. The pump operates at 550 RPM and pumps 0.6 IGPM up to 400 psi using a 1 hp driver. Instrumentation There are four automatic control loops in the test facility. The levels in the crystallizer and the clarifier/thickener are controlled by local level controllers. Both are displacer type instruments. In addition, the flow of clarified brine from the crystallizer and the crystallizer pressure are controlled by automatic controllers. All of the remaining operating parameters are controlled manually. All controllers are pneumatic. Since the unit is designed for use in remote areas, an instrument air compressor and receiver is included on the skid. The only external utility required is electricity and this can be provided by a 35 kW portable generator.

Brine Reheater The rate of precipitation of silica (Si021 from a supersaturated solution is controlled by the kinetics of nucleation and polymerization. Although the seeded crystallizer will reduce the degree of supersaturation, it is not expected to totally stop the precipitation of scaling minerals. Scaling can continue as long as the solution remains above the equilibrium concentration of the precipitating species. The seeded crystallizer will accelerate the approach to equilibrium, but the approach is still asymptotic with respect to time. One means of achieving stabilized brine would be to dilute the brine with fresh waer. In most geothermal regions, however, water is scarce. Also, there may be undesirable side reactions (such as the formation of barium sulfate) when surface water is mixed with brine. Another alternative is to reheat the brine to a temperature above the saturation temperature of the silica. This technique will be tested in the brine reheater. Some of the high temperature steam from the top of the crystallizer vessel will be used to heat the clarified brine in a shell and tube heat exchanger. The brine from the clarifier/thickener will be split into two equal streams with one stream passing through the reheater and one untreated. The effluent streams will be sampled and compared for scaling tendency.

Additional instrumentation is provided for monitoring the facility performance and obtaining operating data. The unit is a proof-of-concept facility and the design objective was to produce a rugged, simple and reliable facility that could be operated in remote and primitive environments, if necessary. Therefore, the use of laboratory type instrumentation was intentionally avoided. Erect ion/Decommissioning The test facility is modular and transportable on three trailers. Figures 4 and 5 show the crystallizer vessel and the main equipment s k i d on their respective trailers ready for transport. The crystallizer test facility is designed to require a minimum of site preparation. A level, unobstructed area, 2 0 ' x 35', preferably with a 12" deep aggregate base to provide good drainage is required for skid erection. No foundations or guy wires are required. The largest and heaviest component of the system is the crystallizer vessel. A 30-ton crane with a 50-foot boom is needed to erect this vessel. The facility consists of six main components, all of which bolt together as well as a small amount of interconnecting piping. The facility can be erec.ted in one day.

At the end of a testing period, the crystallizer body and intervals can be cleaned by any appropriate mechanical means including wire brushing and hydroblasting. PROJECT STATUS The test facility was designed and specified during the period of September through December 1983. All major equipment was specified and procured and received at the construction site by March 1984. Construction was completed during March. In addition to the equipment currently installed in the facility, an extensive assortment of spare parts has been provided. At the end of March 1984, the skid was erected at the fabrication site and all systems were operated as part of the acceptance procedure. The unit was stored at the construction site until November 1984 at which time it was loaded onto trucks and moved to a freight terminal where it currently remains pending transshipment to the first test site. In September 1984 the unit was inspected and regular equipment maintenance was performed.

for the purpose of testing the facility operating characteristics and establishing baseline data. Subsequent test runs will be made to determine the key parameters. Since the Cerro Prieto site is fully developed, it will be possible to support the field testing with complete laboratory services. After the completion of testing at Cerro Prieto, the facility will be transported to other candidate sites to work with brines of varying characteristics. The choice of sites is restricted to those reservoirs with producing wells. In developing areas, the wells are normally operated for only short periods of production testing. However, the mobility and self sufficiency of the test facility should allow testing at these sites since the facility can be moved and erected quickly and easily. REFERENCES 1. Awerbuch, L., Geothermal Scale Control by Crystallization, EPRI AP-2098, November 1981. 2. Awerbuch, L., Scale Control by Upstream Crystallization, EPRI Sixth Annual Geothermal Conference, July 1, 1982.

A draft operating manual has been issued and the final version will be issued when the test plan is finalized. Also a final report on the facility design and construction is in preparation. This report will summarize the work done under RP1525-2 and RP1525-3 and will include equipment data. FIELD TESTS

A number of geothermal sites are suitable for crystallizer testing. Among these are the hypersaline Salton Sea and Brawley reservoirs in Imperial County, and the Cerro Prieto Reservoir in Mexico. Currently, plans are being developed for operating the test facility at Cerro Prieto. The proposed testing would be conducted by the Instituto de Investigaciones Electricas (IIE). IIE has proposed to use the brine from well T-400 in Cerro Prieto 11. A test plan specifically designed for the proposed site is currently being developed. The plan will test the three key design parameters of the crystallizer. These are: 1. Residence Time in Crystallizer Zone 2. Slurry Concentration in Crystallizer Zone 3 . Internal Slurry Recirculation Rate The testing will consist of a series of test runs with one key parameter being varied for each run. The first runs will be primarily

3.

Van der Mast, Dr. V.C., et al, Geothermal Scale Control Using a Flash-Crystallizer-Separator, EPRI AP-3271, September 1983.

T- I F L R S H E R - E T R L L I ZER

SEPRRRTOR

STEM

THIO(ENED

T-2

RTtiosPnZiiZ n n s n

T-3

THICKENER/SETTLER

TRNK

Figure 1.

P r o c e s s F l o w Diagram

-i

4’-6

O.D.

6 I

-

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7

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IL

I Figure 2.

F l a s h C r y s t a l l i z e r Vessel

F i g u r e 3 . C r y s t a l l i z e r Test F a c i l i t y

F i g u r e 4.

Figure 5.

Crystallizer Shipping Configuration

Equipment Skid Shipping Configuration

LESSIONS LEARNED ON BINARY POWER SYSTEMS

John Bigger

Paper Unavailable a t Time o f Publication

c

i

ANALISIS Y PRUEBAS DE TUBERIAS ENTERRADAS CALIENTES Y PRESURIZADAS

I n q . Mario A. Tello de Mengses Ituren I n s t i t u t o de Investiqaciones Elgctricas. Dante 36-60. Piso 11590 Mgxico, D . F . , 5114211

RESUMEN

A f i n de colaborar con l a CFE en l a b6slqueda de una adecuada so-

luci6n tgcnica y econ6mica para l a conducci6n de fluidos en un campo geotgrmico, e l I I E desarroll6 un proyecto denominado Tuberias Enterradas, en e l cual s e estudiaron d i s t i n t o s aspectos relacionados a1 disefio de e s t e t i p 0 de arreglos, t a l e s

CO~O:

materiales de t u b e r l a , rellenos, aislamientos, inhibici6n

o r g h i c a , corrosi6n externa y , muy especialmente, e l a n z l i s i s mec6nico y t&mico.

A1 f i n a l , s e logr6 conjuntar una s e r i e de trabajos sobre e s t e tema, experiencias operativas y constructivas en o t r o s sectores y paises y normas aplicables a1 cas0 con e l objeto de d e s a r r o l l a r una metodologfia que combina l a mecsnica de suelos con e l a n s l i s i s e s t r u c t u r a l de una tuberia.

Para v e r i f i c a r e l comportarniento bajo condiciones r e a l e s de operaci6n, se cons truy6 una tuberfa enterrada de prueba en el Campo Geot&micO de Los Azufres, l a cual fue analizada experimentalmente con e l apoyo del W E M .

A N A L I S I S Y PRUEBAS DE TUBERIAS ENTERRADAS

CALIENTES Y PRESURIZADAS

Ing. Mario A. T e l l 0 de Meneses I t u r e n I n s t i t u t o de Investiqaciones E l g c t r i c a s Dante 36-60. P i s 0 1 3 59.0 M6xic0, D.F., 51 1421 1

SUMARTO A f i n de cola6orar con l a CFE e n l a bfisqueda de una adecuada soluci6n t6cnica y eco_ n6mica p a r a l a conduccidn de f l u i d o s en un campo geot6rmic0, e l I I E d e s a r r o l l d un proyecto d e nominado Tuberias Enterradas, e n e l cual se estudiaron d i s t i n t o s aspectos relacionados a 1 d i seiio de e s t e t i p o de a r r e q l o s , t a l e s como: mate r i a l e s de t u b e r i a , r e l l e n o s , a i s l m i e n t o s , inh i b i c i 6 n orq'mica, corrosidn externa y , muy especialmente, e l a n d l i s i s meetinico y t 6 m i c o .

A1 f i n a l , se logr6 conjuntar una s e r i e de t r a b a j o s sobre e s t e tema, experiencias o p e r a t i v a s y c o n s t r u c t i v a s en o t r o s s e c t o r e s y p a i s e s y normas a p l i c a b l e s a 1 cas0 con e l o b j e t o de d e s a r r g l l a r una metodologia que combina la m e c d n i c a de s u e l o s con e l a n g l i s i s e s t r u c t u r a l de una tuberia. Para v e r i f i c a r e l comportamiento b a j o condiciones r e a l e s de operacibn, se constmy6 una tuber i a e n t e r r a d a de prueba en e l Campo G e o t e n i c o de Los Azufres, l a cual fue analizada experimen talmente con e l apoyo d e l LAPEM. La soluci6n t r a d i c i o n a l para l a conducci6n de f l u i d o s e n un campo geot6rmico implica e l tendido de largos a r r e g l o s de tuber i a s u p e r f i c i a l , con l a consecuente qran c a n t i dad de s o p o r t e s , a n c l a j e s y aislamiento. La d i s t r i b u c i 6 n de una t u b e r i a puede r e s u l t a r no muy s e n c i l l a y e l problema s e agrava cuando e l t e r r e n o p r e s e n t a un r e l i e v e accidentado o cuando se t i e n e n que r e s p e t a r dreas de c u l t i v o , v i vienda o s e r v i c i o piiblico. En e s t o s casos, un a r r e g l o de t u b e r i a s enterradas podria l l e v a r no s610 a una soluci6n t 6 c n i c a para l a c o n d u c c i h de 10s f l u i d o s , s i n o tambidn a una ganancia emn6mica debida a l a reducci6n e n l a longitud de l a t u b e r i a , a l a eliminaci6n de s o p o r t e s y a i s lamiento, a l a menor caida de presio'n y a l a protecci6n ambiental. INTRODUCC~ON

Antes de r e a l i z a r e l a n a l i s i s mecdnico y t 6 m i co de una t u b e r i a e n t e r r a d a , s e deben tomar en cuenta o t r o s aspectos de diseiio, como son: mate r i a l e s , r e l l e n o s i n h i b i c i d n o r q h i c a , absorci6n de expansiones, protecci6n a n t i c o r r o s i v a , et&t e r a , l o que dard 10s lineamientos y c r i t e r i o s en l a s soluciones e s p e c i f i c a s . Dentro de un campo geot6rmic0, podrdn conducirs e d i f e r e n t e s f a s e s de agua: desde l i q u i d 0 sub_ e n f r i a d o a b a j a presi6n o a presidn atmosfe'rica

h a s t a vapor saturado o seco (vapor p r i n c i p a l ) a relativamente a l t a s presiones (8.0 - 8.5 b a r ) y temperaturas (170 - 180°C),pasando por l a s d i f g E l hecho de t e n e r r e n t e s mezclas agua-vapor. e s t a s temperaturas implica l a necesidad de l i z a r a n d l i s i s de f l e x i b i l i d a d para g a r a n t i z a r un comportamiento mecdnico adecuado de l a s tubE r i a s . Los e f e c t o s debidos a l a s expansiones t6rmicas s e v e r h modificados por l a acci6n d e l t e r r e n o que rodea a 10s a r r e g l o s y de alguna manera se deber6 simular l a presencia d e l s u e l o con e l o b j e t o de i n t e q r a r l o en 10s mgtodos t r a d i c i o n a l e s de cdlculo y poder emplear 10s programas de c h p u t o normalmente usados en e l andl i s i s de f l e x i b i l i d a d de t u b e r i a s s u p e r f i c i a l e s .

rea

E l modelo de a n f i l i s i s e s t r u c t u r a l , aunque funda mentado e n l a mec6nica de s u e l o s , debi6 v a l i d a r se, por l o que s e construy6 una i n s t a l a c i d n de prueba en e l Campo Geot6rmico de Los Azufres, en donde s e observo' una t u b e r i a e n t e r r a d a t r a b a jando b a j o condiciones r e a l e s de operacidn y se tomaron mediciones para d e t e m i n a r l a t r a n s f e r e n c i a de c a l o r , 10s desplazamientos en algunos puntos e s p e c i f i c o s a s i como 10s esfuerzos pres e n t e s . E s t e iiltimo logrado con l a ayuda de

LAPEM.

ASPECTOS GENERALES DE DISERO Materia1es.La selecci6n d e l m a t e r i a l de una t u b e r i a e n t e r r a d a e s t a r d en funci6n de v a r i o s par&etros,siendo 10s p r i n c i p a l e s : a). bl c) d) e)

f)

Temperatura de operaci6n Presibn de operacio'n Fase o estado d e l agua ( t i p o de fiuidc) Carqas externas Mantenimiento o r e v i s i o n e s requeridas Confidabilidad en s u us0

En p r i n c i p i o , para t u b e r i a s enterradas en un campo qeot&rmico, s e puede pensar e n t r e s mater i a l e s : p o l i e t i l e n o , asbesto-cement0 o acero a 1 carbo'n. Tuberia de po1ietileno.E l t i p 0 de p o l i e t i l e i o empleado en l a construcci6n de t u b e r i a s debe ser de densidad a l t a (940-960 kg/m3), l o que l e da un esfuerzo permisible a l a tensi6n e n t r e 21 y 28 m a . S i se compara con un m a t e r i a l r i q i d o , l a f l e x i b i l i d a d d e l p o l i e t i l e n o l e d6 caracter i s t i c a s i n t e r e s a n t e s a 1 u s a r s e en una t u b e r € a enter'irli?, ya que l a s carqas e x t e r n a s v e r t i c a -

l e s s e reparten hacia 10s lados, reduciindose l a carqa a c t i v a sobre l a pared del tubo.

a)

riaciones poco bruscas en l a s temperat u r a s del f l u i d o .

Su costo no v a r i a mucho comparado con e l del acero (0.85 a 1 . 2 veces, dependiendo d e l di&g

t r o ) . su r e s i s t e n c i a a l a corrosi6n es excelen t e pero, siendo e l p o l i e t i l e n o un material t e r mopl'lstico, t i e n e como limitaci6n l a temperatur a de operaci6n, encontrhdose su mbimo a 65OC. Una tuberia de e s t e t i p 0 e s muy confiable durant e su operacibn, aunque no e s conveniente usarla e n e l t r a n s p o r t e de f l u i d o s de t r a b a j o ya que, aparte de l a temperatura de t r a b a j o qeneralmente a r r i b a de 6SoC, s e pueden presentar qrandes caidas de presi6n ocasionadas por l a s uniones en sus p a r t e s i n t e r n a s . Tuberia de asbesto-cement0.Ya existen exper i e n c i a s en e l us0 de t u b e r i a s enterradas de asbesto-cement0 conduciendo aqua c a l i e n t e ( 149"CL en un camp qeot'ermico. De acuerdo a 10s repor t e s d e l usuario [3], l a elecci6n de e s t e mate-r i a l r e s u l t 6 mhs ecOn6mica comparado con e l a c e ro, atribuyihdosele un mejor comportamiento ant e l a corrosiBn, expansi6n de l a t u b e r i a y pbrdidas por f r i c c i 6 n . Su m s t o u n i t a r i o s e r i a e n t r e 20 y 40% e l del acero. S i n embargo, l a t u b e r i a en operaci6n ha presentado f r a c t u r a s en alqunas secciones y fugas en l a s uniones, especialmente en l a s juntas de expansi6n. Esto pue de deberse a 1 choque te'rmico ocasionado por una operaci6n d e f i c i e n t e 0 , probablemente, a l a ricjidez propia de l a t u k r l a que l e impide absorber o r e l e v a r cargas externas o por compactaci6n. Adicionalmente, e l manejo de e s t a tuber i a durante s u transportaci6n e instalaciGn, d% be hacerse con extremo cuidado para e v i t a r rupturas . En cas0 de emplear e s t e material en t u b e r i a s en

b)

Requieren mantenimiento y revisiones peribdicas , e s pecialmente en l a s uniones.

c).

Requieren de juntas de expansi6n, l a s cuales, para e s t e t i p 0 de t u b e r i a s , son susceptibles de fugas.

d)

Presentan una probabilidad relativamey? t e a l t a de fedla por f r a c t u r a .

Tuberia de acero a1 carb&.La tuberia de a c e r o a1 car66n e s capaz de soportar l a s condiciones de operaci6n d e l vapor y e l aqua qeot6rmic o s , ademds de permitir e l u s 0 de curvas de expansi6n para absorber l a s dilataciones t k n i c a s y no requerir de elenwntos especiales para su conducci6n dentro y fuera de t r i n c h e r a s . Su capacldad de carqa e5 elevada, l o cual permite mayor f l e x i b i l i d a d en l a forma de i n s t a l a r s e s i n aumentar l a probahilidad de f a l l a . Aunque en alqunos casos se tienen problemas de incrustacidn i n t e r n a , no e x i s t e l a posibilidad de un ataque qufmico t a n filprte como para o r i q i n a r f r a c t u r a s . Por l o que respecta a1 ataque e x t e r no, s e deberh tener cuidado de qarantizar un buen sfstema de protecci6n anticorrosiva. En general, s e puede d e c i r que e l acero a 1 carb6n r e s u l t a l a a l t e r n a t i v a m h s conveniente a usarse en tubercas enterradas conduciendo fluidos de t r a b a j o dentro de un campo g e o t h n i c o . Rel1enos.Prbcticamente todos 10s t i p o s de suelo son susceptibles de s e r usados como relleno, tenisndose como base l a s i q u i e n t e preparacidn :

terradas conduciendo aqua c a l i e n t e , s e recomien da, en base a l a experiencia obtenida, observar 10s siguientes puntos:

b)

La i n s t a l a c i 6 n debe ser hecha por espe

cT

a)

bZ

c)

d)

cialistas. Tomar especial atenci6n en la uni6n de l a tuberfa con 10s equipos, para evitar movimientos por d i l a t a c i h t d m i c a que pueden producir fugas. A 1 operar l a tuberia s e debe manejar e l f l u i d o cuidadosamente para e v i t a r e l choque tdrmico, recomendhdose l a inst a l a c i 6 n de sensores de temperatura a l o largo de l a l i n e a . Usar empaques de acoplamiento a manera de juntas de expansi6n en e l extremo de cada secci6n de t u b e r i a , con e l obj e t o de absorber l a expansi6n t h n i c a .

En tdrminos generales, no s e descarta l a poslble aplicaci6n de e s t e m a t e r i a l o materiales SE mejantes e n tuberfas enterradas conduciendo vapor o agua dentro de un campo qeot6rmico. S i n embargo, cabe r e s a l t a r l a s siquientes desventajas :

L i m i t a l a f l e x i b i l i d a d de operaci6n de 10s pozos a 1 tener que a j u s t a r s e a va-

a)

Remoci6n de materia orqhnica Remocibn de escombros y s6lidos de t a mafio mayor de 25 m. Mezcla con inhibidores orqdnicos

E l r e l l e n o que s e emplea en l a construcci6n de

arreqlos de tuberfas enterradas s e c l a s i f i c a en dos t i p o s : r e l l e n o de fondo y r e l l e n o de cub i e r t a . Se debe cuidar que e l material tenga c a r a c t e r i s t i c a s mecbnicas estables y homoqgneas. Por esa raz&, se l e tendrd que dar gran importancia a su compactaciijn: para e l r e l l e n o de fondo, s e recomienda 90% de s u densidad mbxima; para e l r e l l e n o de cubrerta, 85%. E l r e l l e n o de fondo deberh c o n s i s t i r en una capa de por 10 menos 10 cm por debajo del lecho bajo del tub0 y l l e q a r hasta e l nivel del lecho a l t o . Por :e cima de d s t e y por lo menos con una a l t u r a de 30 cm, se tendrh e l r e l l e n o de cubierta. Para q a r a n t i z a r un adecuado disefio de tuberias enterradas, s e hace necesario conocer l a s propiedades d e l terreno que s e va a emplear como r e l l e n o , destachndose ccmo l a s principales: la cohesiGn, e l Bngulo de f r i c c i 6 n interna y l a

re

s i s t e n c i a a1 esfuerzo cortante (para e l anhlisis mecbnico); l a conductividad tgrmica ( p a r a e l a n h l i s i s tsrmico) y algunas c a r a c t e r f s t i c a s e l g c t r i c a s , como son l a conductividad, l a cont i n u i d a d , e t c . (para e l diseiio de sistemas a n t i corrosivos) .

tm y

En tdrminos g e n e r a l e s , e s recomendable emplear

~y

como r e l l e n o e l mismo m a t e r i a l que se removi6en l a construcci6n de l a t r i n c h e r a donde descansarb l a t u b e r i a . Con e s t o , se abaten 10s c o s t o s 910 b a l e s ya que Re e v i t a r d e l t r a n s p o r t e de mater i a l a1 l u g a r de l a i n s t a l a c i d n . S i n embargo, en s i t u a c i o n e s e s p e c i a l e s , puede e x i s t i r l a necesidad de mezclar o u t i l i z a r t o t a l m e n t e o t r o t i p o de s u e l o d i s t i n t o a 1 de l a zona de const r u c c i 6 n con e l o b j e t o de o t o r g a r l e a 1 r e l l e n o propiedades mecgnicas e s p e c i f i c a s p a r a un d i s e Eo determinado. T a l s e r i a e l cas0 de agregar limo p a r a obtener un r e l l e n o de fondo menos cohesivo o r e d u c i r l a f r i c c i d n l o n g i t u d i n a l de l a t u b e r i a.

6

tu

Aqui cabe hacer n o t a r que l a capacidad de l a b e r i a p a r a s o p o r t a r cargas depende en gran part e de las c a r a c t e r i s t i c a s y condiciones de apoyo con su r e l l e n o de fondo, ya q u e e s t e " m l c h 6 n " darb un e f e c t o de reforzamiento a l a m i s m a t u b e ria.

z

zu B

@

A

Espesor minim0 d e l tubo, m

.., CoefCciepte p o r e f i c i e n c i a de soldadura. ... Asentamiento o desplazamiento d e l t e r r f t no, m ... Desplazamiento 6ltimo d e l t e r r e n o , m

... C o e f i c i e n t e . ..

... . .. ... ...

de r i g i d e z u n i t a r i o p o r u n i dad de l o n q i t u d , m-l Def lexidn de l a pared d e l t u b o , m Angu!o de f r i c c i 6 n e n t r e tubo y t e r r e n o (Tabla I ) 3 peso volumstrico Gel t e r r e n o , N/m Angulo de f r i c c i 6 n i n t e r n a d e l r e l l e n o Espaciamiento e n t r e r e s o r t e s , m

Espesor.E l c6lculo d e l espesor de una t u b e d 2 e n t e r r a d a debe s a t i s f a c e r t r e s c r i t e r i o s : a) b) c)

Esfuerzo p o r tenSi6n e n l a pared presg rizada. Deflexi6n d e l a n i l l o de l a pared p r e s g rizada. Esfuerzo t a n g e n c i a l sobre l a pared.

Para e l primer c r i t e r i o , s e a p l i c a r d l a ecuaci6n dada p o r las normas [ I p a r a e l c h l c u l o d e l espesor de una t u b e r i a p r e s u r i z a d a , e s d e c i r :

3

PD

Este aumento a l a r e s i s t e n c i a se l e da e l

nombre de " f a c t o r de lecho" y v a r i a de un v a l o r de 1 . 1 , p a r a materiales g r a n u l a r e s compactados, a v a l o r e s de 3.4 p a r a fondos de concreto r e f o r zado.

. ..

tm= 2 (Se

+

+ A

(1)

Py)

En e l sequndo c r i t e r i o , s e c a l c u l a r s e l porcent a j e de d e f l e x i 6 n de l a p a r e d , e l c u a l no debeexceder un v a l o r de 5%:

rs

DISERO MECANICO Nomenclatura A

cb CP D E

F1 H

I K

k Kp L P

Pd P1 pv Q q Qu

-

a_

r

... Tolerancia en e l e s p e s o r , p o r roscado, c o r r o s i d n , e t c . , m. ... C o e f i c i e n t e de Boussinesq, (Fig.1)

... c3xIficiente de t r a n s f e r e n c i a de carga vertical. ... D i h e t r o e x t e r i o r d e l tubo, m ... M6dulo de E l a s t i c i d a d d e l m a t e r i a l , N/m 2 ... Fuerza de f r i c c i 6 n l o n g i t u d i n a l , N ... Profundidad de e n t e r r a m i e n t o , m ... Momento p o l a r de i n e r c i a d e l tubo, m 4 ...

Constante de deformaci6n d e l r e s o r t e , N/m M6dulo de r e a c c i s n de subgrado, N/m3 C o e f i c i e n t e de p r e s i d n l a t e r a l d e l terreno. Longitud d e l tubo, m Presi6n i n t e r n a , N/m2 Carga muerta v e r t i c a l , N/m2 Carga v i v a v e r t i c a l , N/m2 Carga v e r t i c a l t o t a l , N/m2 Carga s u p e r f i c i a l concentrada, N Carga s o b r e e l t e r r e n o , N/m2 Carga Gltima s o b r e e l t e r r e n o , N/m2 Carga v e r t i c a l e f e c t i v a , N/m2

... ... ... ... ... ... ... .. . ... ... . .. ... D i s t a n c i a

h o r i z o n t a l de a p l i c a c i d n de Q,

m.

Se

... Esfuerzo mhirno

t

... Espesor

permisible d e l material,

N/m2

d e l tubo, m

En e s t a ecuacidn ( 2 ) , e l v a l o r de Cp v a r i a de 1.0 a 1.5 p a r a v a l o r e s de l a H/D de 0 a 1; C p adquiere v a l o r e s de 1 . 5 a 2.0 conforme H/D se a l e j a de 1.0

La carga v e r t i c a l Pv se determina a p a r t i r de: Pv = Pd

+

(3)

P1

La cargarnuertsPd e s t a r h dada por: Pd = $ H

(4)

La carga v i v a P 1 se c a l c u l a r b usando:

(5)

P 1 = QCb/H2

La carga s u p e r f i c i a l concentra (Q) generalmente se debe a causas t a l e s como ruedas de camiones o f e r r o c a r r i l e s . Este valor debers s e r a f e c t a do p o r un f a c t o r de impacto, pudigndose tomar 10s s i g u i e n t e s : Ferrocarriles:

1 . 5 ( p a r a c u a l q u i e r profundidad)

Autom6viles y Camiones:

1 . 3 (para H = 0 ) 1 . 0 ( p a r a H = 1)

E l c o e f i c i e n t e de Boussinesq (.Cb) es una funci6n de l a r e l a c i 6 n r/H, s e g h s e puede ver e n la figura 1.

0.5

0.4

0

w

;0 . 3

a ) Represw'sci611 d; um. t ! i l ) n r i a e n t e r r a d a

m 0 0 Y

7

ii

0 2

LL

"w 0

0. I

0.0

FIGURA 1.- C o e f i c i e n t e de Boussinesq, como una funcidn de l a r e l a c i 6 n r/H.

Por iiltimo, e l t e r c e r c r i t e r i o a s a t i s f a c e r por un espesor calculado p a r a una t u b e r i a e n t e r r a d a es: PD E t (3Ay/Dl Se>+ (6) 2t D(1-2Ay(D). Modelo de An5lisis.-

b ) Sirnulac&, por medio de r e s o r t e s , de l a i n t e r a c c i 6 n d e l t e r r e n o sobre l a tuberia. F I G U R A 2.- Modelo de an2ilisis de t u b e r i a s ente-

rradas

.

(7)

Para hacer e l an2ilisis de

f l e x i b i l i d a d de una t u r b e r f a e n t e r r a d a con e l f i n de conocer 10s elementos mec8nicos y e s f u e r zos debidos a las expansiones tdrmicas, se propone c o n s i d e r a r e l modelo mostrado e n l a f i g u r a 2 , en donde s e supone a l a t u b e r i a como un e l e mento con l i b e r t a d de movimiento Ctraslaci6n y r o t a c i b n ) y s u j e t o a l a accibn de una serie de r e s o r t e s en s e n t i d o h o r i z o n t a l y v e r t i c a l . cionalmente e x i s t i r d una f u e r z a de f r i c c i 8 n Adi lon g i t u d i n a l , debida a l a accibn d e l t e r r e n o sob r e l a pared de l a t u b e r i a . Tanto l a s constant e s de 10s r e s o r t e s como e l v a l o r de l a s f u e r zas, est& dados fundamentalmente p o r las c a r a g t e r i s t i c a s del relleno.

Relacidn Carga-Deformaci6n

re

d e l Terrene.- La l a c i d n e n t r e l a carga de p r e s i 6 n a p l i c a d a a un s u e l o en determinado momento y s u asentamiento, e s conocida como Mbdulo de Reaccidn de Subgrado, expresado matemgticamente como:

va )r de l a k ( l a p e l d i c n t e de l a curva) , no e s c o n s t a n t e .

E n una g r g f i c a q vs. z , e

La s i q u i e n t e r e l a c i d n h i p e r b d l i c a r e p r e s e n t a sz t i s f a c t o r i a m e n t e l a curva de comportmiento de un t e r r e n o a n t e una t u b e r i a e n t e r r a d a : Z

q=Al+Blz

Por l o t a n t o , s u s t i t u y e n d o en ( 7 ) , se t i e n e :

Los v a l o r e s de A I y B 3 est& e n funci6n d e l d e s plazamiento Gltimo y de l a carqa Gltima d e l t e rreno, calculada de acuerdo a l a t e o r i a de mecg n i c a de suelos:

A1 = 0.145 zu/qU

(301

B1 = 0.855/qU

(13).

Para e l cas0 de t u b e r i a s e n t e r r a d a s , se consi.de r a adecuado tomar 10s s i g u i e n t e s v a l o r e s para e l desplazamiento Gltimo: En direcci6n h o r i z o n t a l con buena compactacidn

de l a r e s i s t e n c i a de l a capa e x t e r i o r e s t 6 dada por : ~1= pqKpL(tan6)

(16)

La carqa v e r t i c a l e f e c t i v a se c a l c u l a r h de l a s i q u i e n t e manera:

-

9

(17)

= Y(H+D/2)

E l v a l o r d e l c o e f i c i e n t e de presi6n l a t e r a l d e l t e r r e n o s e puede tomar como 1.0 para suelos li-

mosos o con arenas f i n a s , y 1 . 3 para 10s demhs. E l dnqulo de f r i c c i 6 n e n t r e l a pared d e l tubo y e l t e r r e n o , puede tomarse de l a Tabla 1 .

(>80%)

zu = 0.015 (H+D/2).

si $ # 0

(12.a)

zu = 0.030 (H)

si $ = 0

(-3 2 ,b).

En d i r e c c i g n h o r i z o n t a l , con poca comDactaci6n (>70%)

#

zu = 0.020

(H+D/2).

si

zu

(H)

si + = O

= 0.050

$J

(12.c)

0

(12.d)

1

I

TIP0 DEL TERRENO

1

6

1

Grava limpia, mezcla de grava y arena Arena limpia, mezcla de qrava y arena limosa Arena limosa, mezcla de qrava o arena con limo o arcilla L i m o arenoso f i n o , L i m o

no-plhsti co

110

En direcci6n v e r t i c a l , con buena compactaci6n zu = 0.100 D

(.I2.e)

En diLecci6n v e r t i c a l , con poca compactaci6n

zu = 0.150 D

(32.f)

.

Constante d e Wforrraci &I de 10s Resortes - La f iqura 2 muestra una tuber2a s u j e t a a l a acci6n de una s e r i e de r e s o r t e s colocados en direcci6n v e r t i c a l y e n direcci6n h o r i z o n t a l . La const% t e de esos r e s o r t e s e s t a r s dada por:

K

=

(13)

k h D

La separaci6n e n t r e r e s o r t e s (A) deberh ser tomada considerzndose l a r i q i d e z d e l elemento de t u b e r f a , para e v i t a r que s e qeneren e f e c t o s de f l e x i 6 n en l a simulaci6n, d i s t i n t o s a 10s que en r e a l i d a d e x i s t e n . Por t a n t o , SR deberh cum_ p l i r que:

(341

XP 40

BUENO

g

30

-

40

0.001

-

0.01

4

3

ACEPTABLE

a

20

-

30

0.01

-

0.1

3

2

BAJO

1

6.8

-

20

0.1

2

1

MUY BAJO

P

0

-

6.8

1

0

< 0.001

- 1

> 1

TENDENCIA A AUMENTAR

+

0.5

-

0.5

TENDENCIA A DISMINUIR

-. 0 . 5

+

0.5

TABLA 5.

EVALUACION DE CEMENTOS EMPLEANDO VALORES R E L A r I v o s .

R E S I S T E N C I A A LA COMPRESION

CEMENT0 TIP0

FOND0 DE P o 2 0 CUBOS CILINDROS

i

PERMEABILIDAD

CAMARAS SUP. FONDO DE CUBOS CILINDROS POZO

CA)~RAS SUP.

TOTAL

3.5

.5 12.5 L

3.5

2.5

2.0

3.0

2

3

16

M

2.5

3.5

2.0

3.0

3.5

3.0

17.5

N

1.5

1.5

3.5

3.5

2.0

3.0

15

P

3.5

3.0

2.5

3.0

3.0

3.5

18.5

w

2.0

2.5

2.0

3.0

1.5

X

4.0

5.0

2.5

2.0

2.5

Y

3.0

2.5

5.0

6.0

3.0

3 .O

3.0

3.5

3.0

5.5

3.0

3.5

21.5

4.0

4.0

3.0

5.0

2.5

3.5

22.0

2

BETA

TABLA 6 .

RESULTADO F I N A L DE LA EVALUACION.

I CEMENTo €'IJNTAJE

LOS

I

MEJORES

Y

D

BETA

B

2

A

22.5

22

22

21.5

21.5

20

ACEPTABLES

X

19

P

18.5

NO PASARON L A S PRUEBAS

M

17.5

17

1G

0 CURADO EN LAB. ( 22hrs. 1 0

3 MESES

A 6 MESES A 12 MESES

FIG. 1 RESISTENCIA A L A COMPRESION DE LOS CUBOS PRECURADOS EXPUESTOS E N E L FOND0 D E L POZO Q757 ( 1 M P a = 10.2 Kg / c m 2 1

60

0 1 DIA 0

0

MESES

A 6 MESES

Q

5

3

50

A 12 MESES

z

0 v)

W

1"

LL

a 2

40

0 0

a

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a a 0 z

30

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t-

cn cn

20

AL

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LL

J

10

I

A

I

B

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1

F

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K

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A

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4 I

W

I

X

I

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FIG: 2 RESISTENCIA A L A COMPRESION DE ClLlNDROS EXTRAIDOS DE LECHADAS FRAGUADAS "IN-SITU'' EXPUESTAS ( 1 MPa

10.2 Kg / c m 2 1

EN E L FOND0 D E L POZO Q 757

I

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3

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a 0

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BETA

CEM ENTO

FIG. 3 PERMEABILIDAD DE LOS CILINDROS EXTRAIDOS DE L A S LECHADAS FRAGUADAS "IN-SITU" EXPUESTAS EN EL FOND0 D E L POZO Q 757.

$

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PERMEABILIDAD EN MICRODARCYS

d

I

LOG. DE L A

NECESIDAD DE UN BANCO DE INFORMACION GEOTERMICA

Por: Arturo Gonzglez Salazar.

-

Para el Desarrollo Inicial de 10s Proyectos Geotgrmicos,

existe deficiencia en la informaci6n geotgrmica disponible, que repercute seriamente en fracasos o excesivos costos en 10s estudios iniciales o el desarrollo de 10s campos geotgr micas.

Los palses que cuentan con experiencia geotgrmica son muy

-

pocos a nivel mundial, existiendo tambign la deficiencia de que experiencias extremadamente valiosas de algunos campos, no se comparten por restricciones de las partes de las - - - compafilas ejecutoras del proyecto.

De manera muy valiosa, la OLADE public6 hace algunos afios, -sus

documentos sobre prefactibilidad y factibilidad para - -

proyectos geot6rmicos, que en Amgrica Latina ha venido a - subsanar esa deficiencia y gran vacio existente.

Sin embargo, afin falta mucho por hacer, siendo necesaria la integracih o formacidn de un Banco de datos geotgrmicos, que le permita a1 inexperto o leg0 en geotermia, tener in-formacidn bgsica, con el fin de evitar el dispendio de re-cursos econ6micos, cada dla m8s escasos, y optimizar la se-

cuela de exploraciones y explotaci6n del Recurso Geotgrmico.

THE NEED FOR A GEOTHERMAL DATABASE BY Arturo Gonzalez Salazar

There is a deficiency in available geothermal information for the initial development of the geothermal projects. This has serious repercussions in terms of failures and excessive costs in the initial studies or in the development of the geothermal fields. The countries that have geothermal experience are very few worldwide. Also, very valuable experiences on some fields are not shared because o f restrictions of the companies executing projects. In a very valuable way, O W E has for-seuera&.years been publishing its documents on prefeasibility and feasibility for geothermal projects, which in Latin America has remedied the deficiency and large gap. Nevertheless, there is still much to do.

It is necessary to compose or form

a geothermal database that will allow the non-expert or layman in geothermy to obtain basic information, so as to avoid the expenditure of economic resources that are ever more scarce; and to optimize the results of the exploration and the working of the geothermal resource.

WORLDWIDE GEOTHERMAL POWER DEVELOPMENT by Ronald DiPippo(l) Mechanical Engineering Department Southeastern Massachusetts University North Dartmouth, Massachusetts ,02747 617-999-8541

SUMMARY OF POWER PLANT DEVELOPMENT Up to the year 1978, geothermal power development had progressed with an average annual growth rate of about 8 . 3 % [l]. From 1978 to the present the growth rate has been about 17%, as can be seen from Fig. 1. Most of the increase has been due to power plant activity in three countries: the Philippines, the United States, and Mexico. If that rate of growth were to continue, then there would be about 10,000 MW of geothermal power on-line by the end of this decade. However, there are indications that a significantly lower growth rate will take hold for at least the next five years.

Table 1 gives a summary of the present status (i.e. , through 1985) and projected developments out to the year 1994 for those countries that now have operating plants and those that might reasonably be expected to have plants during the next 10 years. Based on information available at this time, the cumulative potential geothermal power Since 1970 MW capacity is about 10,114 MW. of this is classified as ''plannedii,i.e., without a specific date (for the United States and the Philippines beyond the year 1989) it is clear that 10,000 MW cannot be achieved by the year 1990. Indeed, it seems likely that an annual growth rate of about 6% will apply for the rest of the 1980s. The rate could increase in the 1990s should the Philippines resume their initial rapid development of their impressive geothermal resources. In this paper we will focus on geothermal power plant activities in the following countries: the United States, Mexico, Japan, New Zealand, Nicaragua, and Indonesia. A thorough worldwide survey has been written for the 1985 International Symposium and will soon be available [ 21.

I

United States Tables 2-4 summarize the status of plants at The Geysers (CA), the Imperial Valley (CA), and the rest of the U. S. , respectively. The planned expansion at The Geysers should reach 2660 MW within the next ten years, using only the dry-steam (1) Also, Div. of Engineering, Brown University, Providence, Rhode Island 02912.

portion of the field. The foreseeable expansion of the plants in the Imperial Valley may lead to an installed capacity of about 414 MW. For the rest of California and the states of Hawaii, Nevada, Oregon, and Utah, the total capacity could reach 257 MW if all plans are fulfilled. Thus, a grand total of 3331 MW is currently Itin the pipeline'!, if not "under the wellheadfl, for the U.S. in the foreseeable future. In the Imperial Valley there are five projects that are about to come into being: (1) the Heber Binary Demonstration Plant; (2) the Heber Flash Plant; ( 3 ) Magma Power Company's Vulcan Power Plant; (4) Ralph M. Parsons' Niland Geothermal Energy Program; and (5) Ormat's Ormesa Modular Binary Project at East Mesa. This year electricity will begin to flow into the grid from the world's largest binary plant, the Heber Binary Demonstration Plant, a 65 MW (gross), 45 MW (net) power plant that uses a mixture of isobutane and isopentane as its working fluid. A demonstration of success, both on technical and economic grounds, will go a long way toward opening up a large number of low-to-moderate temperature geothermal resources. Binary plants are one of the most non-polluting types of power plant that can be conceived, a major advantage in environmentally sensitive areas. However, binary plants still require an independent supply of cooling water, a limitation that could either hamper development or force designers to resort to dry (i.e., air) cooling which generally is more expensive than wet cooling. Roughly one mile to the east of the Heber binary plant, the Heber Flash Plant of the Heber Geothermal Company will also reach the production stage during 1985. It will be a double-flash plant with a net rating of 49 MW. Since these two plants will draw fluid from the same general reservoir, it will be interesting to see if their operations affect one another. They will also serve to show the relative advantages and/or disadvantages of a flash versus a binary plant. The hostile, high-temperature, high-salinity brines of the Salton Seapilandprawley areas are being tamed through the adoption of flash

STATUS AND PROJECTED DEVELOPMENT OF WORLDWIDE GEOTHERMAL POWER

TABLE 1

COUNTRY United States Philippines Mexico Italy Japan New Zealand El Salvador Kenya Iceland Nicaragua Indonesia Turkey China Soviet Union France (Guadeloupe) PortugaI (Azores) Greece (Milos) Costa Rica Guatemala Chile Saint Lucia India Romania Australia

MW as of 1985

MW to be installed each year

Unspec.

2022.11 894.0 645.0 519.2 215.1 167.2 95.0 45.0 39.0 35.0 32.25 20.6 14.321 11.0 4.2 3.0 2.0 0 0

815.0 1155.0

__

380.0 108.0

-_ 85.0 -_-_ 110.0 --

0.55 150.0

_----

15.0 15.0 30.0 1.0 1.0 0.5

0

0 0 0 0

Totals, each year Cumulative total

2866.9 4763.981

10113.6

3.9

/

6.I '10

17% annual growth

W

3.6

/

5 a

0

3.5.

-

1

/

0

3.4 0

a0

3.3

I

3.0

I

ACCTUPL 0 PAOJECTED

( 1,000 MW) I

'75

I

I

I

I

I

I

,

'85

'80 YEAR

FIG. 1 GROWTH OF GEOTlfERMAL POWER: 1975-1990.

I

crystallizers and reactor-clarifiers. Magma Power company, the holder of patents on this process, is building the Vulcan Power Plant at the site of the old Dept. of Energy Geothermal Loop Experimental Facility (GLEF) The plant, scheduled to begin operating late in 1985, will produce 34.5 MW of saleable power which will be purchased by SCE. The power system is a double-flash type with separate high- and low-pressure turbines each with its own generator; the turbines are being supplied by Kitsubishi Heavy Industries, Ltd. The turbines will have the following technical specifications:

.

HP turbine: rating, 27.73 MW maximum capability, 30.16 MW speed, 3600 rpm steam inlet conditions: pressure, 517.1 kPa temperature, 162.7OC gas content, 1.3% by w t . flow rate, 58.3 kg/s exhaust pressure, 6.77 kPa last-stage blade height, 584.2 mm type: double-flow impulse-reaction 6 stages per flow. LP turbine: rating, 8.88 MW

maximum capability, 9.56 MW speed, 3600 rpm steam inlet conditions: pressure, 100.3 kPa temperature, 107.2OC flow rate, 31.5 kg/s exhaust pressure, 6.77 kPa last-stage blade height, 635 mm type: single-flow impulse-reaction 3 stages. The Ralph M. Parsons company is constructing a double-flash plant at Niland, the Niland Geothermal Energy Program (NGEP) The first phase will produce 38.6 MW of net power, and should be completed in mid-1986. Clean, high-pressure steam will be generated using a separated-steam condenser/reboiler arrangement that removes the large amount of noncondensable gases (9% by weight of steam). Additional HP steam will be flashed from the liquid portion of the geofluid separated at each wellhead. A low-pressure flash vessel will generate Lp steam for use in the lower stages of the turbine being supplied by Fuji Electric Company. The two turbines will have separate condensers. The -design specifications for phase 1 call for steam inlet conditions of 167.7OCI 689.5 kPa (HP) and 117.5OCI 124.1 kPa (LP);exhaust pressures of 5.42 kPa (HP) and 7.72 kPa (LP). After at least one year of operation, 31.4 MW may be

.

added to the plant through additional wells and some modification to the turbine. The HP steam pressure and temperature would remain unchanged, but the LP conditions would be modified to 124.2OCI 155.8 kPa, and the condensers would operate at 6.91 kPa (HP) and 12.29 kPa (LP). Parsons is the owner of the wells, the brine processing equipment, and the power plant; SCE will purchase the power through the Imperial Irrigation District (IID)

.

At the East Mesa field, the portion originally under lease to Republic Geothermal, Inc. is about to be developed by Ormat Systems, Inc. through a partnership called Ormesa Geothermal. The plan is to install 26 individual, modular binary units, each with a gross rating of 1.25 MW, to produce 20 MW of net saleable power. The power units are under construction at Ormat's manufacturing facility although not all pieces of the agreement are yet in place. It is expected that the equipment for cooling and electrical systems will be on site during 1985, and that power will come on line in 1986. Outside California, activity has picked up in Nevada and Utah. About 105 MW is scheduled to be on line in Nevada by 1987; about 30% of this capacity will be in binary units. In Utah, 41.5 MW should be on line by 1986 in two fields: Roosevelt Hot Springs and Cove Fort/Sulphurdale. The first power generated from geothermal energy in Nevada came from a 60 kW binary unit at Wabuska Hot Springs in 1984. The plant is a skid-mounted unit manufactured by Ormat and has logged over 4000 hours of operation at this writing. The resource temperature is 106OC; the well is about 107 m deep; a 75 kW pump assists production, boosting the flow rate from an artesian flow of about 9 kg/s to 45 kg/s; and cooling water is handled in a spray pond and recirculated to the plant's condensers. The power equipment was delivered to the site in April 1984, preliminary runs were made in July 1984, and in September the plant was on line. The owner of the plant is Tad's Enterprises of Orinda, CA; power is sold to Sierra Pacific at 5.1 cents/kWh. Another binary power project is under construction at Brady Hot Springs, Nv by Munson Geothermal, Inc. , of Reno. MGI holds about 12,480 acres under lease at Brady and plans to install 2.8 MW by the end of 1985 with a follow-on of 5.5 MW through the rehabilitation of the Raft River Dual-Boiling Binary Plant. The 2.8 MW will be achieved by running 6-9 modular units from Ormat. Reservoir fluid temperature is about 149OC, and the wells will probably be pumped. Power will be sold to Sierra Pacific.

TABLE 2 PLANT( 1)

GEOTHERMAL POWER PLANTS AT THE GEYSERS, CA, USA YEAR -

MW -

1960 1963 1967 1968 1971 1972 1973 1975 1979 1980 1980 1979 1989 1982 1983 n.a. 1985 1988 n.a. n.a. n.a. 1985 1983 1983 1985 1984 1985 n.a. n.a. 1987 1988 n.a.

11 13 27 27 2x53 2x53 2x53 106 106 133 109 59 114 114 114 55 114 140 114 114 114 1.2 110 72 55 80 2x55 110 55 55 55 55

PGbE Geysers: Unit 1 Unit 2 Unit 3 unit 4 Unit 5-6 Unit 7-8 Unit 9-10 Unit 11 unit 12 Unit 13 Unit 14 Unit 15 Unit 16 Unit 17 Unit 18 Unit 19 Unit 20 Unit 21 Unit 22 Unit 23 Unit 24 wild well NCPA 2 SMUDGEO No. 1 Bottlerock OXY 1 NCPA 3 Modesto GEO South Geysers SMUDGEO No. 2 CCPA NO. 1 CCPA NO. 2

STATUS Operational Operational Operational Operational Operational Operational Operational Operational Operational Opera tiona1 Operational Operational Under construction Operational Operational Preliminary planning Under construction Advanced planning Preliminary planning Preliminary planning Preliminary planning Advanced planning - Operational Operational Operational Operational under construction Preliminary planning Advanced planning Preliminary planning Under CEC review Preliminary planning

__ 1792 2660.2

Totals:

Operational(2) Oper., u.c.. or planned

(l)A11 units are dry-steam type except Wild Well unit which will be a binary plant. ( 2 ) Includes plants under construction and scheduled for completion in 1985.

TABLE 3

GEWHERMAL POWER PLANTS IN THE IMPERIAL VALLEY, CA, USA

PLANT East Mesa: B.C. McCabe NO. 1 Magma Unit 2 Magma Unit 3 ORMESA (Ormat) Salton Sea: Geothermal Electric project (Union/SCE/ SPLC/MPC) vulcan Power Plant (Magma/SCE) Niland (NPN Partnership) Niland Geothermal Energy Program (Parsons): Phase 1 Phase 2 Heber: Binary Demo Plant Flash Plant (HGC) North Brawley Westmorland South Brawley (CU I )

YEAR -

TYPE -

1979 n.a. n.a. 1986

Binary Binary Binary Binary

1982

1-Flash

10.0

Operational

1985 n.a.

2-Flash 2 F1ash

34.5 49.0

Under construction Planned

1986 1988

2-Flash 2-Flash

38.6 31.4

Under construction Planned addition

1985 1985 1980 1988 n.a.

Binary 2-Flash 1-Flash Binary Flash

45.0 49.0 10.0 15.0 49.0

Under construction Under construction Ope rational Planned Planned

161.0 219.62 414.02

operational' Operational or U.C. oper., U.C., or planned

-

Totals:

MW 12.5 25.0 25.0 26~0.77

STATUS

Operational Planned Planned Under construction

*Includes plants under construction and scheduled for completion in 1985.

TABLE 4

GEOTHERMAL POWER PLANTS IN THE UNITED STATES (EXCLUDING THE GEYSERS AND THE IMPERIAL VALLEY)

PLANT -

YEAR -

TYPE -

1986 n.a.

l-Flash 1-Flash

1984

Binary

2x3.5

Operationa1

1985 1987

Binary Hybrid: wood-geothermal

5x0.6 20.0

Under construction Under construction

Hawaii Puna No. 1

1982

1-Flash

3.0

Operational

Idaho Raft River

1982

Binary

5.0

Being moved to Brady H.S., NV

1984 1985

Binary 2-Flash

0.6 17.0

Operational Under construction

1985 1986 1985 1986 1986 1985

2.8 5.5 5.5 15.0 10.0 9.0

Under construction Under construction Planned Planned Planned Under construction

1987 1987

Binary Binary Binary Binary Flash ( ? ) Total Flow/ 2-Flash Z-Flash Flash

20.0 20.0

Planned Planned

1983 1984

Binary Binary

1984 1986

1-Flash Total Flow/ 2-Flash

1985 1985 1986

Binary Binary Dry steam

4~0.675 2xl.O 2.3

Operational Under construction Advanced planning

Totals:

69.11 134.11 256.91

Operational* Operational or U.C. Oper., U.C. or planned

MW -

STATUS

California

cos0: Unit 1 Unit 2-3 Mammoth : Mammoth-Pacif ic Chance Ranch (Wood Associates) Honey Lake

25.0 2x25.0

Under construction Advanced planning

&

Nevada Wabuska Hot Springs Beoware Brady Hot Springs: Phase 1 Phase 2 Steamboat Springs Fish Lake Big Smokey Valley Desert Peak Spring Creek Dixie Central Oregon Hammersly Canyon: Unit 1-3 Unit 4-6

3x0.30 3x0.37

Operational Operational

Utah Milford: Blundell unit I Wellhead No. 1 Cove Fort-Sulphurdale: Phase 1 Phase 2 Phase 3

20.0

14.5

Operational Under construction

*Includes plants under construction and scheduled for completion in 1985.

Binary plants are also being planned for Steamboat Springs and Fish Lake in Nevada. At Steamboat Springs, Geothermal Development ~ssocs.plans to install seven modular Ormat units: four 1200 kW units and three 800 kW units. A net power of about 5.5 MW is expected. Reservoir fluid temperatures are 160°C at 152 m; wells will be pumped to prevent flashing. A 10-year power purchase agreement is in place with Sierra Pacific. At the Fish Lake prospect, the fluid temperature is in the range 188-200°C as determined by the discovery well drilled in 1984 and the confirmation well completed in January 1985, Although a binary-type plant has been decided upon, the manufacturer has yet to be selected. A total of 15 MW is expected to be installed by the end of 1986. Two 20 MW flash plants are in the planning

stage for Dixie Valley (Spring Creek and Dixie Central) by Trans-Pacific Geothermal Company. They may be on line by 1987. The Beoware resource will be tapped by a double-flash steam plant. Mitsubishi Heavy Industries, Ltd. has the turbine/generator under construction and expects to have the 17 MW on line by the end of 1985. The plant will be owned by Chevron USA Beoware. Power will be purchased by Southern California Edison through Sierra Pacific. innovative 9 MW double-flash plant incorporating a rotary separator turbine is under construction at Desert Peak. The power conversion equipment will be built by Transamerica Delaval 1nc.--Biphase Energy Systems. The Biphase double-flash system proved more efficient and cost effective than competitive energy conversion systems. Ground was broken for the plant in January 1985 and the plant should be completed late in 1985.

An

Two resources in southern Utah are being developed but in different ways. A 20 MW single-flash plant, Blundell Unit I, came on line in 1984 at Milford (Roosevelt Hot Springs). Because of the high temperature of the resource (26OoC), the geofluid carries a significant amount of silica (510 ppm) and silica scaling has been a concern during operation. A wellhead unit is under construction at Milford that will use the Biphase rotary separator expander in conjunction with a dual pressure steam turbine to generate a net power of 14.5 MW. Mother Earth Industries (Cove Creek Geothermal) will have four Ormat binary units in place at its Cove Fort-Sulphurdale prospect by June 1985. Each unit has a gross output of 800 kW and the net power for sale from the first four units will be about 2.7 MW. Power will be purchased by the City of Provo. Phase 2 of the project will involve

the installation of two more units, each 1 MW net, by the end of 1985. Phase 3 , to be completed in 1986, envisions the addition of a steam turbine in a topping mode to make efficient use of the dry steam being produced by the wells. The energy of the exhaust from the turbine will be harnessed by the binary units from Phases 1 and 2, which will then be operating in a bottoming mode. Altogether the six binary units and one steam turbine should produce about 6.5 MW net. Mexico Table 5 lists the geothermal projects in Mexico; these include plants at three fields--Cerro Prieto, Los Azufres, and Los Humeros. A total power capacity of 1290 MW is planned for these areas by the year 1993. This vigorous development program has propelled Mexico into third place among those countries generating electricity from geothermal energy. Other fields, such as La Primavera, are being explored and may eventually reach the production stage. m n There are nine geothermal power plants in Japan, ranging in size from 0.1 MW at the Kirishima Kokusai Hotel to 55 MW at the double-flash Hatchobaru plant. The plants are located on three of the Japanese islands: Honshu, Kyushu, and Hokkaido. The total rated capacity is 215.1 MW including 22 MW from a dry-steam plant (Matsukawa), 88.1 from six single-flash plants (Otake, Onuma, Onikobe, Kakkonda, Suginoi Hotel, and Kirishima Kokusai Hotel), and 105 Mw from two double-flash plants (Hatchobaru and Mori). Expansion of some of the existing plants is being given serious consideration. Step-out drilling is underway, for example, at Hatchobaru in preparation for the construction of The situation is another 55 MW unit. summarized in Table 6. The newest geothermal plant in Japan is at the Kirishima Kokusai Hotel. Roughly 20% of the power requirements of this hotel are supplied by a single-flash geothermal unit having a 100 kW non-condensing turbine. The plant came on line in February 1984; the turbine-generator was built by Fuji Electric Co., Ltd. The turbine runs at 3600 rpm; steam inlet conditions are 127"C, 247 kPa (saturated) with 0.06% noncondensable gases (by volume); exhaust pressure is 117 kPa. The generator is air-cooled and rated at 125 kVA at 440 V. Hot water from the wellhead separator is piped to the hotel for use in a bathing spa. The facility is located in Kagoshima in the southern part of Kyushu within the scenic Kirishima National Park. A 50 MW double-flash plant known as Mori was put on line in November 1982 at the Nigorikawa area in Mori-machi on the southwest part of Hokkaido. See Fig, 2. The plant is operated by the Hokkaido Electric Power Co., Ltd. ; the ste'am field was developed by Dohnan

TABLE 5 PLANT Pathe Cerro P r i e t o U n i t 1-2 U n i t 3-4 Unit 5 Cerro P r i e t o U n i t 1-2 Cerro Prieto unit 1 Unit 2 Cerro P r i e t o U n i t 1-2 Los A z u f r e s : W.H. U n i t W.H. U n i t unit 1 W.H. U n i t Unit 2 unit 3 Unit 4 W.H. U n i t L o s Humeros: W.H. U n i t Unit 1 Unit 2

GEOTHERMAL POWER PLANTS I N MEXICO

YEAR

TYPE -

MW -

STATUS

1959

1-Flash

3.5

De-commissioned

1973 1979 1981

1-Flash 1-Flash 2-Flash

2x37.5 2x37.5 30.0

1984

2-Flash

2x110

1985 1985

2-Flash 2-Flash

110 110

1992

2-Flash

4x55.0

Planned

1982 1982 1986 1987 1988 1989 1990 1993

Dry Steam 1-Flash 2-Flash 1-Flash 2-Flash 2-Flash 2-Flash 1-Flash

2x5.0 3x5.0 50 7x5.0 55 55 55 lOx5.0

Operational Operational Under c o n s t r u c t i o n Advanced p l a n n i n g Advanced p l a n n i n g Advanced p l a n n i n g Advanced p l a n n i n g Advanced p l a n n i n g

1987 1990 1991

1-Flash 2-Flash 2-Flash

3x5.0 55 55

Under c o n s t r u c t i o n Advanced p l a n n i n g Advanced p l a n n i n g

To t a 1s:

425 710 1290

I:

Opera t i o n a 1 Operational Operational

11:

Operational

111:

Under c o n s t r u c t i o n Under c o n s t r u c t i o n

IV:

1-2 3-5 6-12

13-22 1-3

TABLE 6

Operational O p e r a t i o n a l o r U.C. Oper., U.C. or p l a n n e d

GEOTHERMAL POWER PLANTS I N JAPAN

YEAR -

TYPE Dry Steam

22.0

Operational

1- F l a s h

12.5

Ope r a t i o n a l

Mor i

1966 1967 1973 1975 1977 1978 1978 1978 1981 1982

1-Flash 1-Flash 2-Flash 1-Flash Binary Binary 1-Flash 2-Flash

10.0 12.5 55.0 50.0 1.0 1.0 3.0 50.0

Operational Operational Operational Operational Dismantled Dismantled Operational Operational

K i r ishima K o k u s a i Hotel H a t c h o b a r u I1 Kakkonda I1 S u g i n o i 11

1984 n.a. n.a. n.a.

1-Flash 2-Flash Flash 1-Flash

0.1 55.0 50.0 3.0

Operational Advanced p l a n n i n g Advanced p l a n n i n g Early planning

PUNT Matsukawa Otake

Onuma Onikobe Hatchobaru Ka k konda Otake P i l o t Nigorikawa P i l o t S u g i n o i Hotel

Totals:

Mw -

215.1 323.1

STATUS

Operational Operat.iona1 or planned

Geothermal Energy Co. , Ltd. , with the cooperation of Japan Metals Chemicals Co., Ltd. [ 31.

\

The site is characterized by a relatively flat basin of about 3.75 km2 at 100 m above sea level surrounded by hills rising to about 250 m. Roughly 60 hot springs exist in the basin; six resort hotels use the hot water for bathing spas, and greenhouses are supplied with hot water. Permeability was discovered in fractures extending along the caldera wall. Seventeen deep wells have been drilled: six are used for production, seven for injection, and four were unsuccessful. Two more wells (D-7 and D-8) are scheduled for drilling. The fractures associated with the caldera wall are being used as injection sites whereas production wells are drawing from fractures associated with a northeast-trending fault and through the Pre-Tertiary formation within the basin itself. See Fig. 3. The wells are clustered in four areas, drilling sites B, C, D and F. See Fig. 4 . All successful wells have been directionally drilled. Data on the successful wells are shown in Tables 7 and 8. Two-phase pipelines carry the geofluid from wells F-1 and F-9 to the separator/flasher station located at well-site D. Short two-phase pipelines run from wells D-1, D-3, D-5 and D-6 to the separators. Three vertical, bottom-outletcyclone separators can each produce 56 kg/s of steam; three horizontal flash vessels can generate 2 2 kg/s of low-pressure steam. The HP and LP steam are transmitted to the plant via separate pipelines, a distance of about 1.5 km. There are about 600 m of two-phase piping and 1700 m of hot water piping. owing to the high levels of noncondensable gases, mainly carbon dioxide, it is necessary to use a turbo-driven centrifugal compressor to remove the gases from the condenser. This is also the reason for the rather high condenser pressure. Furthermore, the production wells have been subject to calcite plugging at the flash horizon due to CO liberation. In fact, soon after the plant started operating, the plugging was so severe as to reduce the plant output from 50 MW to 15 MW. Initially the problem was addressed by re-drilling to remove the deposits and by treatment of the wells with acid. More recently, a scale inhibitor has been successfully injected into the flowing wells below the flash horizon. The inhibitor interrupts the association of calcium and carbonate ions. Through this technique, power production has been restored to about 35 MW. Full production should be achieved with the completion of the new production wells in well-pad D.

Otaru City 4T

[

1

I Yakumo-machi o\

y,

I

The Oshima Peninsula Mori-machi y q

I I

1

ran City Nigorikawa area

a

k

e

42'

- The Kameda Peninsula

Peninsula

__

FIG.2

SW HOKKAIDO SHOWING NIGORIKAWA AREA.

Design specifications for the power plant are given in Table 9. Three site photographs are presented in Plates 1-3 [Courtesy of Dr. H. Nakamura, Japan Metals & Chemicals Co., Ltd. 1.

Hew Zealand

The principal geothermal generating facility in New Zealand is at Wairakei, the site of the world's first commercial geothermal power plant using fluid from a liquid-dominated resource. Only 11 of the original 13 power units (installed from 1959-1963) are still in operation. However, the two units that have been removed from service because of the decline in reservoir pressure and the loss of high-pressure steam (Units 5 and 6) are being rehabilitated for use at the Ohaaki double-flash power plant now under construction. These two 11.2 MW back-pressure turbines will be matched with two new 56.9 MW machines to be supplied by Mitsubishi Heavy Industries, Ltd., to give the Ohaaki plant a rated capacity of 116.2 MW.

FIG.3

NIGORIKAWA AREA SHOWING S I T E S OF MORI POWER PLANT AND WELL PADS.

Site C C t

Hot water

/

Secondary steam

.Two phase flow Sebarator \ \ e Hot t'Lw

Site B 0

0.1

0.2

0.3

0.L

0.5

km

L

scale ( a p p r o x . )

FIG.4

GEOFLUID TRANSMISSION SYSTEM FOR MORI POWER PLANT.

Site F

TABLE 7 Total depth

Total depth

Well

m

m

D-1 D- 3 D-5 D- 6

2400 2320 736 2205

F-1 F- 9

2464 2340

PRODUCTION WELL DATA AT MORI, JAPAN Flow R a t e s , kq/s

Main

Secondary

steam ( 1)

2143.5 2089.0 683.9 2106.3

16.9 36.8 21.7 15.6

2355 2221.7

18.9 -

7.1 -

146.7

36.8

Totals:

( 1 ) P r e s s u r e = 786.5 k P a ;

NC G a s e s

steam (2)

Residual water

% (vol.) of steam

6.3 11.9 15.1 3.6

72.8 136.7 173.3 41.9

0.53 4.80 2.50 0.91

9.7

111.7 81.4

3.99 1.23

53.7

617.8

( * ) P r e s s u r e = 266.7 k P a .

PLATE 1 MORI POWER PLANT.

TABLE 8

INJECTION WELL DATA AT MORI, JAPAN Total depth

Vert. depth

Flow rate(1) kg/s

Well -

m m -

B-2

1973

1552.5

27.1

c-1

1773

1732.9

32.2

F-2 F-5 F-6 F- 7 F-8

2025 998 2383 1464 1785

1945.8 975.3 2229.6 1359.7 1708.4

115.0 118.9 102.8 102.8 54.5

Totals:

476.9

( l ) P r e s s u r e = 639.4 k P a .

TABLE 9

DESIGN SPECIFICA?-I ONS FOR MORI POWER PLANT

Date of start-up Plant type Plant operator No. production wells No. injection wells Turbine data: Manufacturer Rated capacity Type

PLATE 2

PLATE 3

CYCLONE SEPARATORS FOR MORI PLANT.

TIJRBINE HALL FOR MORI PLANT: (R-L)

TURROCOMPRESSOR, TURBINE,

GENERATOR, EXCITER.

November 1982 Double flash Hokkaido Electric Power Co., Ltd. 6

7 Toshiba Corporation 50 Mw Single-cylinder, double-flow, impulse blading, 5x2 3000 Kpm 686.7 kPa 164. 2OC 146.7 kg/s 193.6 kPa 119.2oc 53.7 kq/s 17.6 kPa 508 mm

Speed Main steam pressure Main steam temperature Main steam flow rate Secondary steam pressure Secondary steam temperature Secondary steam flow rate Exhaust pressure iast stage blade height Generator data: 55,600 kVA Capacity Voltage 11.000 v 5 0 Hz Frequency Speed 3000 rpm Condenser data: Type Low-level, direct-contact Pressure 17.6 kPa Cooling water flow rate 2085 kg/s (approx.) Cooling water inlet temperature 25OC Gas extractor data: Type Centrifugal compressor, driven by turbine shaft Power requirement 3,100 kW Cooling tower data: Type Counterflow, mechanically induced draft, octagonal shape Water flow rate 2640 kg/s (approx.) Water inlet temperature 53.6OC Water outlet temperature 25.OoC Design wet-bulb temperature 17. O°C No. fans 4

TABLE 10 PLANT Wair a ke i: Unit 1 Unit 2 Unit 3 Unit 4 Unit 5-6 Unit 7-8 Unit 9-10 Unit 11 Unit 12-13 Kawe r a u Ohaak i: Unit 1

GEOTHERMAL POWER PLANTS IN NEW ZEALAND

YEAR -

TYPE -

1959 1958 1959 1959 1962 1959 1960 1962 1963 1961

SCSF-IP-NC SCSF-HP-NC SCSF-HP-NC SCSF-I P-NC SCSF-HP-NC SCSF-LP-C SCSF-LP-C 2-Flash 2-Flash 1-Flash

11.2 6.5 6.5 11.2 2x11.2 2x11.2 2x11.2 30.0 2~30.0 10.0

Operational Dismantled Dismantled Operational To be installed at Ohaaki Operational Operational Operational Operational Operational

1988

2-Flash

2x11.2 2~46.9

Under construction

167.2 283.4

Operational Operational or under construction

Totals:

The new turbines will have the following characteristics: rating, 46.9 EIW speed, 3000 rpm inlet steam conditions: pressure, 446.8 kPa temperature, 147.1 "C gas content, 5.6% (by weight) flow rate, 94.4 kg/s exhaust pressure, 8.24 kPa last-stage blade height, 584.2 mm type: double-flow impulse-reaction 5 stages per flow. A study is being made of generating an additional 5 MW at Wairakei by using a bottoming binary cycle powered by the waste hot water that is now discharged to the Waikato River. All together 167.2 MW is now on line in New Zealand at two sites; by 1988 there should be 283.4 Mhr on line. See Table 10. Of the numerous geothermal areas in New Zealand, those with the brightest prospects for power development are: Mokai, Rotokawa, and Tauhara.

MW -

STATUS

producing power in September 1983. It is located close to the shore of Lake Managua in its northwest area and on the southern flank of the Momotombo volcano. This is only one of many geothermal areas that stretch along Nicaraguals southwest zone, roughly 50 km inland from the Pacific Ocean. See Fig. 5. A site photograph is shown in Plate 4 [Courtesy of ELC-Electroconsult, Milan, Italy]. Exploration for geothermal anomalies dates from 1966 when the Italian firm ELC-Electroconsult conducted a preliminary study. In 1969 a study by Texas Instruments resulted in a listing of ten areas with geothermal potential. The fumaroles of the south Momotombo volcano were considered the best prospect when the study was completed in 1971. A power potential of at least 35 MW was established as a result of these studies. The San Jacinto area was also deemed a good prospect for commerical development.

Nicarauuq [Note: The following account is based largely on a paper entitled IIEstado Actual del Proyecto Geotermico de Nicaragua11 by the Instituto Nicaraguense de Energia (INE) presented at a meeting of Latin American countries and reported in IIEstado Actual de la Geotermia en America Latinaft, Emloracion Seminario0 - 5 Geotermia, Quito, Ecuador, Sept. 1983, OLADE/BID/INECEL; in Spanish. ]

Following the devastating Managua earthquake of December 23, 1972, all geothermal development work was temporarily halted. In Kay 1974 the Nicaraguan electric authority, then called the Empresa Nacional de Luz y Fuerza (ENALUF), rehired the original consulting firm, ELC-Electroconsult, to complete the feasibility study at Momotombo. At the same time, a contract was signed with the Belgian drilling company Foramines to construct four dual-purpose wells to serve as both exploration and, if successful, production wells,

The first geothermal plant in Nicaragua, the 35 MW single-flash plant at Momotombo, began

Following this phase, ENALUF began the production drilling phase by hiring

14'

'/

NICARAGUA

ATIANTIC OCEAN

V SAN CRISTOBAL-CASK4 S. JACIN?V, EL MYO. hfOMOTOMBO-GAL+W

/

MANAGU - CHlLTEPE

I20

PACIFIC OCEAN COSTA RlCA

FIG.5

MAP OF NICARAGUA SHOWING GEOTHERMAL AREAS.

PLATE 4 MOMOTOMRO POWER PLANT, LOOKING S-SE TOWARD LAKE: MANAGUA.

Energeticos, S. A. and the California Energy Company to drill 12 wells and to manage the drilling program, respectively. By 1978, this task was complete. In 1980 the current electric authority, (INE), secured financing for the project through the Organizacion Latinoamericana de Energia ( O W E ) with the aid of a special OPEC fund. The decision was reached in 1981 to build a 35 MW plant at Momotombo.

Institute Nicaraguense de Energia

The wells were drilled in two stages: Stage 1 from November 1974 to August 1978; Stage 2 from October 1982 to June 1983. During stage 1, 32 wells were drilled resulting in 20 production wells and 4 injection wells. During Stage 2, three wells were completed: one producer (for the anticipated second power unit) and two injectors. Generally the wells for exploitation are constructed using the following casing schedule: 20" conductor casing from 0-20 m; 13-3/8" anchor casing from 20-250 m; 9-5/Ettproduction casing from 150-350 m; and 71' slotted liner from 350-600 rn. Table 11 contains some data on the production wells. Reservoir temperature is in the 23OoC range. TABLE 11

Well MT-2 MT-3 MT-4 MT-9(1) MT-10 MT-12 fl) MT-17 MT-19 MT-29 (1) MT-21 MT-22 MT-23f1) MT-25 MT-26 MT-27(1) MT- 3 1

PRODUCTION WELL DATA AT MOMOTOMBO, NICARAGUA

wellhead elevation m, a s 1

-

Total depth

616

-69

402

85

310

68

821

-

442

Enthalpy kJ/kg

m

80

87

Flow rates steam water

12 18 8 13 7 20 8 4 32 6 11 16 10 17 26 12

48 77 8 57 7 20 32 16 32 28 49 69 45 73 114 98

1100 1100 2700 1100 2700 2700 1100 1100 2700 1100 1100 1100 1100 1100 1100 950

(1)= supplying Unit 1.

There are two production horizons in the field, one shallow and one deeper. Most of the wells intercept the shallow zone which is much better understood than the deeper zone. It will be necessary to exploit the deeper reservoir in a carefully integrated manner with the shallow zone in order to expand the power production of the field beyond the current rating of 35 MW. The deep zone may have temperatures considerably in excess of 230°C. The production wells are outfitted with individual bottom-outlet-cyclone separators. Steam is gathered from the wells and delivered to the plant via two main steam

lines. The separated hot water is collected and distributed to the four injection wells that are located to the south and east of the main production area. See Fig. 6. Some data on the injection wells is given in Table 12. TABLE 12

Well MT-6 MT-15 MT-18 RMT-2

INJECTION WELL DATA AT MOMOTOMBO, NICARAGUA Wellhead elevation m, as1 109

66 74 63

Total depth

m 580 649 1124 1170

The power plant consumes a total of 77.81 kg/s of steam (main steam plus ejector steam) at 165"C, saturation conditions. The gross specific steam consumption is about 8 kg/kW.h; the net consumption is 8.5 kg/kW.h. Assuming an average wellhead dryness fraction of 26.8% and a reservoir condition of saturated liquid at 23OoC, the plant would have a Second Law utilization efficiency of 55.7% (gross), or 52.2% (net). The auxiliaries require 2.2 Mw of power. Efficiencies this high are more often associated with plants of the dry-steam type such as those at The Geysers in California. Several of the wells, in fact, have been observed as tending toward dry steam. The wellhead enthalpy of 1100 kJ/kg seems to indicate a deeper parent reservoir in the temperature range 250-255°C. The shallow wells apparently intercept a two-phase aquifer from which the steam phase is produced preferentially, thus leading to higher than expected wellhead qualities: i.e., if the main reservoir consisted of saturated liquid at 23OoC, one would expect wellhead enthalpies in the 990 kJ/kg range and dryness fractions of about 14%. Table 13 lists the design specifications for the first power unit at Momotombo. Financing for a duplicate second unit has been arranged, and construction should begin soon. Jndonesia The ultimate geothermal power potential of Indonesia is estimated to be 10,000 MW, an impressive figure by any standards. Exploration and/or development are taking place at 18 areas in Sumatera, 29 areas in Java, 16 areas in Sulawesi, and 14 areas in Bali, Lesser Sunda Islands and Moluccas. An ambitious program is underway to get power plants on line in eight different areas by the year 1994. See Table 14. At present, there are two wellhead units (2.25 MW, total) and one central station (30 MW) in operation. The next plants to be built

PRODUCllON WELLS MT-II e

e

REINJECTION WELLS

MT- 7

-COOLING

e

TOWER

MT-I

M1-IZ

.

POWER HOUSE

e

MT- i7

MT-13

ge9 Irl

j%24 MT-20

MT-3

e T- I

MT-18

500 m LAKE

Scale

MANAGUA

FIG.6

F I E L D LAYOUT F O R MOMOTOMBO U N I T 1

TABLE 13

DESIGN SPECIFICATIONS FOR UNIT 1 MOMOTOMBO POWER PLANT

Date of start-up Plant type Plant owner No. production wells No. injection wells Turbine data: Manufacturer Rated capacity Maximum capacity Main steam pressure Main steam temperature Main steam flow rate Exhaust pressure Condenser data: Type Pressure Gas extractor data: Type Steam consumption Cooling tower data: Type No. cells

September 1983 Single-flash INE 5 4 Franco Tosi (Italy) 35 Mw

40.37 MW 700 kPa 165OC 73.37 kg/s 12.5 kPa

Low-level, direct-contact 12.5 kPa Steam jet ejectors 4.44 kg/s Counterflow, mechanically induced draft 4

TABLE 1 4 PLANT Kamojany: wellhead Unit Unit 1 Unit 2 Unit 3 U n i t 4-5 Oieny: wellhead Unit Unit 1 Unit 2 Dar a j a t: Unit 1 Unit 2 Salak: Unit 1 unit 2 unit 3 Unit 4 Lahendony: U n i t 1-2 Cisolok: Unit 1 Unit 2 Banten: unit 1 Unit 2 Beduya 1: Unit 1

GEOTHERMAL PWER PLAEFPS I N INDONESIA YEAR 1978 1982 1987 1988 n.a.

TYPE -

m -

o r y Steam o r y Steam Dry S t e a m o r y steam Dry S t e a m

0.25 30.0 55 55 2x55

STATUS

Operational Operational Under c o n s t r u c t i o n Under c o n s t r u c t i o n Preliminary planning

1-Flash Flash Flash

2.0 55 55

Operational Advanced p l a n n i n g Advanced p l a n n i n g

1991 1992

Flash Flash

55 55

Planned Planned

1988-89 1989-90 1992 1993

Flash Flash Flash Flash

55 55 55 55

Advanced P l a n n i n g Advanced p l a n n i n g Planned Planned

1992-93

Flash

2x15

Planned

1993 1994

Flash Flash

55 55

Planned Planned

1993 1994

Flash Flash

55 55

Planned Planned

1990-91

Flash

55

Planned

1980 1988-89 1989-90

Totals:

32.25 142.25 997.25

will be Units 2 and 3 at Kamojang (2 x 55 MW) and are scheduled to begin operation in the middle of 1987 and early 1988, respectively. Power plants are scheduled for the following areas by 1994: Dieng (112 MW by 1990), Darajat (110 MW by 1992), Salak (220 MW by 1993), Lahendong (30 MW by 1993), Cisolok (110 MW by 1994), Banten (110 MW by 1994), The reservoir and Bedugal 55 MW by 1994). at Kamojang produces dry steam; the others are liquid-dominated.

Operational o p e r a t i o n a l or U.C. o p e r a t i o n a l , U.C. or p l a n n e d

Kazunari Kuriyama, Mitsubishi Heavy Industries, Ltd. Jim Moore, California Energy Company Steve Munson, Munson Geothermal, Inc. Hezy Ram, Ormat Systems Margaret Rands, Imperial County public Works Dept. Tom Seesee, Ralph M. Parsons Russ Tenney, Magma Power Company Bill Teplow, Trans-Pacific Geothermal, Inc. Jack Wood, Wood & Associates References

Acknowleduements The author is happy to acknowledge the help of a large number of people in compiling this report: Ken Boren, GeoProducts, Inc. Gustavo Calderon, Interamerican Development Bank George Crane, Southern California Edison Bill Dolan, Steam Reserve Corp. Martha Eickhof, Pacific Gas & Electric Co. Clem Giles, The Ben Holt Company Sue Hodgson, California Div. of Oil and Gas Zvi Krieger, Ormat Systems

[I] DiPippo, R., !*Worldwide Geothermal Power Development-1984 Overview and Updatebb,Geoth, Resources Council BULLETIN, Vol. 13, No. 9, Oct. 1984, pp. 3-12. [2] DiPippo, R. , bbGeothermalElectric Power-The State of the W0rld--1985*~, Geoth, Resources Council TRANSACTIONS, Vol. 9, 1985. To be published. [3] Dohnan Geothermal Energy Co., Ltd., "Geothermal Development in the Nigorikawa Area, Hokkaido, Japanll, 1984.