Geophysics | Modeling the temperature-dependent electrical conductivity of Berea sandstones

Electrical surveys are widely used for the exploration of geothermal energy, a clean and renewable resource that can help to support the sustainable development of our society. Efforts have been made to increase the understanding of the temperature effects on the electrical properties of reservoir rocks, which will help in the interpretation of electrical survey data. However, there has been no valid rock-physics model for the electrical conductivity of sandstones with varying temperature that can practically aid the quantitative interpretation of electrical survey data for geothermal energy. We have developed an approach for modeling the temperature-dependent electrical conductivity of clean Berea sandstones. Using theoretically inverted values for the aspect ratio of the insulating grains and for the aspect ratio of the temperature-induced variation in the porosity of the microcracks, in combination with the calculated temperature-dependent brine conductivity, the modeled electrical conductivity across varying temperatures compares satisfactorily with a published data set on five Berea sandstones, with relative errors of better than ±5% in all cases. The results indicate the applicability of the developed approach for modeling the temperature-dependent electrical conductivity of sandstones with a minor amount of clay minerals, thereby paving the way for improved quantitative interpretation of electrical survey data in the exploration of geothermal energy.