Electrical Conductivity Imaging Using Controlled Source Electromagnetics For Subsurface Fluid Flow Characterization

In this paper we present a case history for mapping electrical conductivity using Controlled Source Audio Magnetotellurics (CSAMT). We have completed a first pass 1D inversion of a 3D CSAMT data set collected over a geothermal reservoir located in western Idaho. We compare the inversion results of data combinations including apparent resistivity, phase, and direct inversion of the electric field component. The 1D profiles from the first pass inversion are combined to generate 2D subsurface conductivity images. We include our interpretation of the subsurface conductivity structure to determine the pathways of the fluid conduits in the geothermal reservoir. Our eventual goal is to obtain a 3D conductivity model by inverting these data using 3D CSAMT inversion.