Rock conductivity and fractal nature of porosity |
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| Authors: | Clotilde Ruffet Yves Gueguen Michel Darot |
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| Institution: | Institut de Physique du Globe, 5 rue RenéDescartes, 67084 Strasbourg cédex, France. |
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| Abstract: | While the d.c. electrical properties of a rock, through the volume conductivity, provide information on pore space structure (Formation factor) and pore fluid, the frequency dependence of the electrical parameters allows the characterization of the pore-matrix interfaces. To illustrate these properties, we present here some results of measurements performed on sedimentary rocks (Vosges and Fontainebleau sandstones). These samples have a classical electrical response, i.e. a ‘Cole and Cole’ frequency behaviour near a certain relaxation frequency and a low-frequency dispersion. We discuss some of the models that have been proposed in the past to explain this behaviour. It appears that most of them are valid near and above the relaxation frequency, but only Dissado and Hill's model seems to be satisfactory over the whole frequency range. The fractal nature of the interfaces, assumed in two of these models but appropriate only for one of them, could also be a convenient explanation for the frequency dependence. |
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