The aspect of the change in the liquid permeability of rock using distilled water and brine has been reported to be different from that of using gas according to confining pressure Pc and pore pressure Pp. In this study, as part of the research on CO2 geological storage, the permeability of sandstone was measured using supercritical CO2 which has gas and liquid properties simultaneously, and the effect of Pc and Pp on this permeability was analyzed. For supercritical CO2 to be utilized, the series of non- Darcy flow tests with high flow rate were conducted, and the permeability was estimated through the Forchheimer equation considering an inertial flow. An effective pressure coefficient for permeability was derived experimentally to be applied to the effective pressure law. First, we investigated pressure conditions with identical permeability for plotting the iso-permeability line. From the effective pressure law, the effective pressure coefficient of permeability corresponds to the slope of the iso-permeability line. As a results, upon the confining or pore pressure conditions, varied permeability and effective pressure coefficient indicated. To clarify the variation of the coefficient depending on the pressure conditions, we attempted to drive a second-order effective pressure coefficient for which the interaction between Pc and Pp was considered. The coefficient increased non-linearly as the difference of Pc and Pp decreased, with a maximum of 1.36 being observed. The validity and correlation between the effective pressure with the coefficient and the permeability were examined by applying empirical models of permeability dependent on effective pressure.

1. Introduction

Previous studies have demonstrated that the liquid permeability of rock with distilled water and brine is different by variation in the confining pressure Pc and pore pressure Pp (Wei et al., 1986). It is important to acknowledge that the supercritical CO2 (here after scCO2) permeability of rock should be examined by taking account of the properties of the supercritical phase midway between the gas and liquid states.

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