Characterization of Geothermal Reservoir Conditions Using Electrical Surveys: Some Preliminary Results

Abstract

A goal of the present work is to use existing data sets for the operating Basin and Range geothermal reservoirs to test the utility of electrical surveys for characterizing the subsurface. Numerical simulations will be performed to approximately reproduce the observed electrical signals for one or more Basin and Range geothermal power generation projects for which both an adequate reservoir description and useful electrical surveys are available. The results of the case studies will be used to characterize the electrical signals that may be observed from “hidden” geothermal reservoirs. For purposes of the preliminary calculations presented hereunder, we utilize a simplified version of a two-dimensional model of the Dixie Valley geothermal field developed by McKenna and Blackwell. The STAR geothermal reservoir simulator was used to compute a quasi-steady natural state. The DC postprocessor was subsequently utilized to reproduce the distribution of resistivity in the subsurface inferred from various geophysical surveys. Finally, DC and MT postprocessors were used to compute results for a traverse of the geothermal area. Although the geophysical postprocessors approximately reproduce the subsurface resistivity distribution, for various reasons, it proved to be difficult to make a detailed comparison between the results of STAR calculations and the field surveys.