Compartmentalization of the Coso East Flank geothermal field imaged by 3-D full-tensor MT inversion

Geophysical Journal International
By: , and 

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Abstract

Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of low resistivity (2–5 Ohm m) and appreciable lateral extent (>1 km) in the producing zone of the East Flank field. However, these models could not reproduce gross 3-D effects in the recorded data. We perform 3-D full-tensor inversion and retrieve a resistivity model that out-performs previous 2-D and 3-D off-diagonal models in terms of its fit to the complete 3-D MT data set as well as the degree of modelling bias. Inclusion of secondary Zxx and Zyy data components leads to a robust east-dip (60†) to the previously identified conductive East Flank reservoir feature, which correlates strongly with recently mapped surface faults, downhole well temperatures, 3-D seismic reflection data, and local microseismicity. We perform synthetic forward modelling to test the best-fit dip of this conductor using the response at a nearby MT station. We interpret the dipping conductor as a fractured and fluidized compartment, which is structurally controlled by an unmapped blind East Flank fault zone.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Compartmentalization of the Coso East Flank geothermal field imaged by 3-D full-tensor MT inversion
Series title Geophysical Journal International
DOI 10.1093/gji/ggw408
Volume 208
Issue 2
Year Published 2017
Language English
Publisher Oxford Academic
Contributing office(s) Earthquake Science Center
Description 11 p.
First page 652
Last page 662
Country United States
Other Geospatial Coso Range