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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 7. (July)

First Page: 977

Last Page: 977

Title: Geology and Geothermal Energy Development at Coso KGRA: ABSTRACT

Author(s): James L. Moore, Carl F. Austin, Harold J. Prostka

Article Type: Meeting abstract

Abstract:

The Coso geothermal area, located east of the Sierra Nevada about 150 mi (240 km) north of Los Angeles, is in an oval structural basin 25 to 28 mi (40 to 45 km) across that is defined by arcuate faults. The basin is underlain by fractured Mesozoic granitic rocks that have been intruded and partly covered by late Cenozoic basalt, dacite, and rhyolite. A partly molten silicic magma body < 1 m.y. old is interpreted to underlie the central part of the basin. Fumaroles are associated with the youngest volcanics (^sim 0.3 m.y. old) which occur along the upfaulted north-trending Coso Range in the center of the basin. Snow melt patterns along the Coso fault zone, east of the range, indicate high heat flow. Measured heat flow values in exploratory wells indicate > 10 HFU in 11.6 km2 (30 km2) area within the basin. Several young faults cut Pleistocene lavas and offset Holocene alluvium by as much as 10 ft (3 m). The principal structural controls of subsurface fluid flow are fractures, dominantly of north-south, but also of northwest and northeast trend. Maximum measured temperature of surface water is 96.7°C. Compositions of test well fluids indicate reservoir temperatures as high as 250°C and suggest the presence of an extensive chloride-rich hot water system. Development of the geothermal power-generating potential of 3,000 acres (1,215 ha.) within the 72,640 acre (29,400 ha.) Coso KGRA by California Energy Co., under contract with the Department of the Navy, was begun with the siting of four wells in early 1981. The initia exploratory drilling phase will be completed by the 2d quarter of 1982. Commercial power production is anticipated by 1985.

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