GEOLOGIC FRAMEWORK OF THE EAST FLANK, COSO GEOTHERMAL FIELD: IMPLICATIONS FOR EGS DEVELOPMENT

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Conference Proceedings: GEOLOGIC FRAMEWORK OF THE EAST FLANK, COSO GEOTHERMAL FIELD: IMPLICATIONS FOR EGS DEVELOPMENT

Abstract
The Coso Geothermal Field is a large, high temperature system located in eastern California on the western edge of the Basin and Range province. The East Flank of this field is currently under study as a DOE-funded Enhanced Geothermal Systems (EGS) project. This paper summarizes petrologic and geologic investigations on two East Flank wells, 34A-9 and 34-9RD2 conducted as part of a continuing effort to better understand how the rocks will behave during hydraulic and thermal stimulation. Well 34A-9 is the hottest well at depth in the East Flank, reaching nearly 350oC. The reservoir on the East Flank is dominated by diorite and granodiorite. Specifically, the diorites are several different quartz diorites and diorite. Thick intervals of granite, a minor rock type throughout most of the field, were encountered in 34A-9 and 34- 9RD2. The granite tends to be much less altered, veined, and fractured than the other rock types, and thus probably a poor stimulation target. Late stage vein minerals include calcite, quartz, chlorite, and hematite at shallow depths and rare epidote, chlorite, quartz, adularia, and wairakite in the deepest portions of East Flank wells. The distribution of mineral assemblages suggest well 34A-9 was drilled through the caprock and into the uppermost part of the reservoir rocks of a relict geothermal system. The temperatures indicated by the clay minerals are much lower than would be predicted from the present day downhole temperatures, but are in good agreement with fluid inclusion temperatures. These relationships imply the system is currently being reheated...

Authors 
Kovac, K.M.; Moore, J.N.; Lutz and S.J.








Published 
PROCEEDINGS, Thirtieth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, January 31-February 2, 2005, 1/1/2005





DOI 
Not Provided
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Citation

Kovac, K.M.; Moore, J.N.; Lutz, S.J.. 1/1/2005. GEOLOGIC FRAMEWORK OF THE EAST FLANK, COSO GEOTHERMAL FIELD: IMPLICATIONS FOR EGS DEVELOPMENT. Proceedings of (!) ; (!) : PROCEEDINGS, Thirtieth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, January 31-February 2, 2005.


Related Geothermal Exploration Activities
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Areas (1)
  1. Coso Geothermal Area
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