Surface Conductivity, Pore Radius Distribution and Their Effect to Electrical Dispersion: Study in Shaly Sandstones

Abstract

Abstract- Surface conductivity plays as a dominant factor particularly in shaly media. The surface conductivity is indicated by electrical resistivity dispersion in low water saturation. In this case, pore geometry should be considered because large structure is easier to saturate rather than small structure. The objectives of this study are to evaluate pore radius distribution and surface conductivity of the shaly sandstone and their effect to electrical dispersion. Petrographic image analysis was firstly analyzed to asses pore geometry of the media. Pore radius distribution was calculated to evaluate their effect to electrical dispersion. Several results of study are: pore radius distribution and saturation give contribution on electrical dispersion. The large structure reflects more electrical dispersion compare than small pore structure. In high water salinity, surface conductivity occurs at low water saturation degree and vanishes with more water saturation addition. This indicates volumetric effect is now replacing the surface conductivity. Evaluation on electrical resistivity of shaly sandstone should be taken into the account their surface conductivity. Not only the conductor but also the capacitive behavior of the medium should be considered to evaluate the conductivity.

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