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Title: A Reservoir Assessment of the Geysers Geothermal Field

Big Sulphur Creek fault zone, in The Geysers Geothermal field, may be part of a deep-seated, wrench-style fault system. Hydrothermal fluid reservoir may rise through conduits beneath the five main anomalies associated with the Big Sulphur Creek wrench trend. Upon moderately dipping, fracture network. Condensed steam at the steep reservoir flank drains back to the hot water table. These flanks are defined roughly by marginally-producing geothermal wells. Field extensions are expected to be on the southeast and northwest. Some geophysical anomalies (electrical resistivity and audio-magnetotelluric) evidently are caused by the hot water geothermal field or zones of altered rocks; others (gravity, P-wave delays, and possibly electrical resistivity) probably represent the underlying heat source, a possible magma chamber; and others (microearthquake activity) may be related to the steam reservoir. A large negative gravity anomaly and a few low-resitivity anomalies suggest areas generally favorable for the presence of steam zones, but these anomalies apparently do not directly indicate the known steam reservoir. Monitoring gravity and geodetic changes with time and mapping microearthquake activity are methods that show promise for determining reservoir size, possible recharge, production lifetime, and other characteristics of the known stream field. Seismic reflection data may contribute to the efficientmore » exploitation of the field by identifying fracture zones that serve as conduits for the steam. (DJE-2005)« less
Authors:
; ; ;
Publication Date:
OSTI Identifier:
860865
Report Number(s):
CDC-81-111
Resource Type:
Technical Report
Research Org:
Californina Department of Conservation, Division of Oil and Gas
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
Geothermal Legacy