Lawrence Berkeley National Laboratory
Compartmentalization of the Coso East Flank geothermal field imaged by 3-D full-tensor MT inversion
- Author(s): Lindsey, NJ
- Kaven, JO
- Davatzes, N
- Newman, GA
- et al.
Published Web Locationhttps://doi.org/10.1093/gji/ggw408
© The Authors 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society. Previous magnetotelluric (MT) studies of the high-temperature Coso geothermal system in California identified a subvertical feature of lowresistivity (2-5Ohmm) 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 Zxxand Zyydata 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.