Geophysical Characterization of the heat source in the Northwest Geysers, California

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Abstract

The Geysers, in northern California, is the largest energy producing geothermal field in the world. Looking to expand capacity, the operator Calpine Corporation developed an anomalously hot (~400 °C at 2.5 km depth) part of the field in the northwest Geysers, including testing of an enhanced geothermal systems (EGS). Though the area is anomalously hot, geophysical methods have failed to adequately image any inferred magmatic heat source. Gravity measurements were collected and jointly modeled with existing magnetic data along a two-dimensional profile aligned with an existing geologic cross-section. The key feature of the potential field model is a low-density, low-susceptibility body below the EGS at 5 km depth. Magnetotelluric (MT) measurements were collected around the northwest Geysers and modeled in three-dimensions to characterize subsurface resistivity structure. The resistivity model images an extension of a Quaternary granitic pluton locally known as “the felsite” under the EGS project and a possible zone of partial melt (<10%) below 7 km in the northwestern part of the field.

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Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Geophysical Characterization of the heat source in the Northwest Geysers, California
Year Published 2019
Language English
Publisher Stanford University
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 7 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings, 44th Workshop on Geothermal Reservoir Engineering
Conference Title 44th Workshop on Geothermal Reservoir Engineering
Conference Location Stanford, CA
Conference Date February 11-13, 2019
Country United States
State California
Other Geospatial Northwest Geysers