A simulation study of electrical conductivity of porous rocks: effect of clay, porosity, temperature and Peclet number.

Abstract

This study investigates the impact of clay content and temperature variation on the electrical conductivity of three-dimensional fluid-filled porous rocks. The role of varying pore throat radii has been included in the course of clay fraction variation in the conducting channels of the rock samples. The research identifies a critical ratio of clay conductance to fluid conductance that dictates the regime of electrical conductance behaviour. A nonlinear increase in electrical conductance is observed when the clay-to-fluid conductance ratio exceeds the critical ratio, whereas a linear relationship is maintained below this critical ratio. A modified form of Archie's law relating effective conductivity and porosity has been proposed for the clay coated channels. The intricate relationship between Peclet number, pore throat size, and temperature on the electrical conductivity of fluid-filled straight channels in three dimensions has also been investigated. Results revealed a quadratic increase in conductance with porosity under steady-state conditions across all Peclet number ranges examined. While the conductivity remained constant with porosity for each Peclet number, the rate of increase in conductivity diminished with it. Nonlinear increase in conductivity was observed with temperature in the transient flow regime with a threshold temperature marking the onset of conductivity. Conductivity was augmented with increase in observation time in the transient state for the entire temperature range considered. Close to the attainment of saturation in electrical conductivity, the conductivity changed linearly with temperature until a steady value was reached.