The Relationship between Pore Radii and Induced Polarization Studied with a Membrane Polarization Model

Abstract

Summary The induced polarization (IP) method has some potential to estimate hydraulic conductivity of the subsurface. One approach is based on theories predicting relationships between pore radii and IP relaxation time. Recently, laboratory data were discussed where several samples exhibit large relaxation times that do not correspond with large pore radii, and thus seem difficult to explain. Here, we study the relationship between pore geometry and relaxation times using a model of membrane polarization that is based on two cylinders with different pore radii and lengths. By choosing appropriate parameter combinations, we are able to match relaxation times of measured data for given dominant pore radii. The key to explaining large relaxation times without large pore radii lies in the choice of large pore aspect ratios. We also show that the set of parameters that is necessary to match the data lies in the so-called wide pore regime, where the relaxation time is controlled by the length of the wider of the two pores.