In experiments on the electrical properties of rocks at high frequencies, the measured current has both conduction and displacement currents, and these are related to the bulk conductivity and dielectric permittivity, respectively. In the present model, the bulk electrical conductivity of a specimen is taken to be a constant given by Archie's rule, whereas its frequency-dependent permittivity is taken to be a generalization of Sillars' model of a composite dielectric, which treats the pores as being an assemblage of spheroidally shaped inclusions with different orientations and aspect ratios. The conductivity of these spheroids, that is, the conductivity of the pore fluid, influences the frequency dependence of the permittivity in accord with available data. When applied to the dielectric data obtained in experiments on saturated rocks, the model yields distributions of pore shapes. These distributions are used to estimate the electrical response of oil- and water-wet rocks that are unsaturated.--Modified journal abstract.

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