A quick method for estimating pore throat radii of shale using a combination of pressure transmission and capillary breakthrough measurements

Abstract

A rapid and easy to conduct methodology has been proposed for preliminary estimation of pore throat radii and permeability of tight rocks such as shale. Pressure transmission and capillary breakthrough pressure tests were performed on three different shales (A, B and C) to develop a modified Poiseuille equation to estimate shale permeability. This was made possible by correlating the pore throat radius obtained from the pressure transmission test with the pore throat radius obtained from the capillary breakthrough pressure test. Results show that the modified Poiseuille equation has successfully predicted shale permeabilities that were reasonable and fell within the acceptable range of known shale permeabilities reported in the literature. In order to verify the validity of the modified Poiseuille equation, three different shales D, E and F with unknown permeabilities were investigated. The estimated permeabilities for shales D, E and F using the modified Poiseuille equation matched, with the exception of few variations, those obtained by conventional pressure transmission testing. The few variations could be related to the fact that the contact angle was assumed to be zero in the modified Poiseuille equation.