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

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.