Correlating azimuthal anisotropy to geothermal resource potential using a 3D-3C seismic survey of Soda Lake geothermal field, Nevada
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This 3D-3C seismic survey greatly improves the structural model of the Soda Lake, Nevada geothermal system. The goal of determining a “geothermal indicator” in the seismic signal is approached here by looking at seismic anisotropy in a smoothed version of the 3D converted-wave data. Processing of the 3D converted-wave data was limited due to both a high near-surface VP/VS ratio which under-sampled shear-wave energy and the maximum geophone offset which limited the incidence angles. The 3D converted-wave data that we can image shows encouraging similarity to the deep structural features in the P-wave sections, but has little resolution of shallow structures. Smoothing the absolute value of seismic amplitudes along these deep reflections allows for time shift analysis of the diffuse reflections. The reflections that demonstrate higher than 1% anisotropy appear to be controlled by shallow structural features and occur in areas with longer more continuous faults that strike N-S. A correlation is observed between varied fault strike and geothermal production. This study demonstrates the potential for future studies to map out brecciated zones with multiple fault strikes for geothermal resource development.