Cuttings Analysis At Coso Geothermal Area (1985-1987)

GEOTHERMAL ENERGY

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Exploration Activity: Cuttings Analysis At Coso Geothermal Area (1985-1987)

Exploration Activity Details
Location	Coso Geothermal Area
Exploration Technique	Cuttings Analysis
Activity Date	1985 - 1987
Usefulness	useful
DOE-funding	Unknown

Exploration Basis

Analyze an indicator of high permeability zones within a geothermal field

Notes

Petrographic and geochemical analyses of cuttings from six wells in the Coso Hot Springs geothermal field show a systematic variation in the occurrence, texture, and composition of sericite that can be correlated with high permeability production zones and temperature. The wells studied intersect rhyolitic dikes and sills in the fractured granitic and dioritic basement rocks which serve as the reservoir for the geothermal system. Low-permeability non-productive zones in the wells contain coarse-grained compositionally homogeneous primary muscovite. High-permeability production zones are characterized by abundant fine-grained hydrothermal sericite that exhibits a systematic increase in K and Al and decrease in Si with increasing temperature. These calculations suggest that hydrothermal sericites are in local equilibrium with the geothermal fluid, but primary muscovites in low permeability zones are metastable.

References

• Bishop, B.P.; Bird, D.K.   (1 January 1985) Correlation of hydrothermal sericite composition with permeability and temperature, Coso Hot Springs geothermal field, Inyo County, California

• Bishop, B.P.; Bird, D.K.   (1 May 1987) Variation in sericite composition from fracture zones within the Coso Hot Sprints geothermal system