A comparison of laboratory measured electrical conductivity in rocks with theoretical conductivity based on derived pore aspect ratio spectra

Abstract

Compressional and shear wave velocities and electrical conductivity have been measured simultaneously on three saturated samples of granite up to 0.4 GPa effective pressure and one of chalk up to 0.04 GPa effective pressure. The velocity–pressure data have been inverted using the non-interactive theory of Kuster & Toksöz to produce pore aspect ratio spectra. Archie's Law, and a model devised by Hoening have been used to calculate a theoretical electrical conductivity from the derived pore spectra. In general there is good agreement between the observed conductivity and the conductivity calculated using Hoening's equation applied to ‘cigar-shaped’ cracks. Predicted conductivities obtained via Archie's Law are in approximate agreement using a power of two and are much less than the observed values using a power of one. The results suggest that simultaneous electrical conductivity measurements might provide an important constraint in interpreting velocity—pressure data in terms of pore spectra.