| Title | Comments on Some of the Drilling and Completion Problems in Cerro Prieto Geothermal Wells |
|---|---|
| Authors | B. Dominguez A., G. Sanchez G. |
| Year | 1981 |
| Conference | DOE-CFE Symposium on Cerro Prieto |
| Keywords | |
| Abstract | From 1960 to the present, 85 wells with a total drilling length exceeding 160,000 m have been constructed at Cerro Prieto, a modest figure compared to an oil field. This activity took place in five stages, each characterized by changes and modifications required by various drilling and well-completion problems. Initially, the technical procedures followed were similar to those used in the oil industry. However, several problems emerged as a result of the relatively high temperatures found in the geothe'rmal reservoir. Stated briefly, the various problems that have been encountered can be considered to be related to drilling fluids, cements and cementing operations, lithology, geothermal fluid characteristics, and casings and their accessories. Similarly, the criteria used for well completion initially followed those commonly used in oil wells. However, as the importance of high temperatures and the characteristics of the geothermal reservoir fluids were better understood, the criteria were modified to optimize well-completion operations, and very satisfactory results have been achieved to date. We consider that reasonably satisfactory solutions have been found to most of the problems. Nonetheless, some of the solutions need to be further optimized, and other problems need better answers, as in the case of corrosion damage to the casings. With regard to well completions, the criteria need to be improved, especially to identify formations saturated with hot waters. We think that a systematic lithologic and mineralogic analysis, as well as petrographic analysis of hydrothermal and metamorphic minerals combined perhaps with rock geochemistry and x-ray analysiS, would ultimately yield better methods of maximizing the extraction of the energy stored in the reservoir. De 1960 a la fecha, se han perforado en Cerro Prieto 85 pozos, con un total que excede a 160,000 m., cifra modesta si se compara con las perforaciones realizadas en pozos petroleros. Esta actividad se ha desarrollado en cinco etapas, distinguiendose cada una por cambios y modificaciones para resolver problemas diversos, tanto en la perforacion como en la terminacion de los pozos perforados. Inicialmente, los procedimientos tecnicos se ajustaron a los utilizados en la perforacion de pozos petroleros, sin embargo, surgieron varios problemas que en esencia tenlan como origen las temperaturas relativamente elevadas que en este campo se han detectado en el reservorio geotermico. En forma resumida, los distintos problemas detectados se pueden referir a: fluidos de perforacion, cemen tos y cemen taciones, caracterlsticas litologicas y contenido de fluidos geotermicos, tuberlas de ademe y sus accesorios. En forma similar, los criterios para la terminacion de los pozos inicialmente siguieron los habituales en pozos petroleros, pero a medida que se entendio mejor la importancia de la temperatura y las caracteristicas de los fluidos geotermicos contenidos en el reservorio, se modifico dicho criterio para optimizar las terminaciones, lograndose a la fecha resultados muy satisfactorios. Las soluciones logradas para la mayor parte de los problemas, consideramos que son razonablemente satisfactorias, no obstante que deberan optimizarse algunas y encontrar respuesta mas conveniente para otras, como es el caso de los danos por corrosion en las tuberias de ademe. En cuanto a las terminaciones, debera optlmlzarse el criterio, sobre todo para la discriminacion de formaciones impregnadas de agua caliente, por medio de analisis litologicos y mineralogicos, asi como petrograficos, relativo a minerales hidrotermales y metamorficos, auxiliandose tal vez con geoquimica de rocas y aun analisis de rayos X, pensamos que este sistema dara a la postre las soluciones mas satisfactorias para obtener la mayor cantidad de energla almacenada en el reservorio. |