Geological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California

Technical Report · Mon May 01 04:00:00 EDT 1978

DOI:https://doi.org/10.2172/5754045· OSTI ID:5754045

Galbraith, R M

The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California, from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and extensive geophysical logging surveys were conducted to document the geologic character of the geothermal system as penetrated by CGEH-1. The major rock units encountered include a mafic metamorphic sequence and a leucogranite which intruded the metamorphic rocks. Only weak hydrothermal alteration was noted in these rocks. Drillhole surveys and drilling rate data indicate that the geothermal system is structurally controlled and that the drillhole itself was strongly influenced by structural zones. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system. Several geophysical logs were employed to characcterize the drillhole geology. The natural gamma and neutron porosity logs indicate gross rock type and the accoustic logs indicate fractured rock and potentially permeable zones. A series of temperature logs run as a function of time during and after the completion of drilling were most useful in delineating the zones of maximum heat flux. Convective heat flow and temperatures greater than 350/sup 0/F appear to occur only along an open fracture system encountered between depths of 1850 and 2775 feet. Temperature logs indicate a negative thermal gradient below 3000 feet.

• Research Organization: Utah Univ., Salt Lake City (USA). Research Inst.
• OSTI ID: 5754045
• Report Number(s): IDO-78-1701.b.4.2
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150303* -- Geothermal Exploration & Exploration Technology-- Exploratory Drilling & Well Logging
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CALIFORNIA
CAVITIES
COSO HOT SPRINGS
DRILLING
EXPLORATORY WELLS
GAMMA LOGGING
GEOLOGIC STRUCTURES
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GEOTHERMAL GRADIENTS
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SONIC LOGGING
TEMPERATURE GRADIENTS
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WELL DRILLING
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WESTERN REGION