Effect of Sub-core Scale Heterogeneity on Relative Permeability Curves of Porous Sandstone in a Water-supercritical CO2 System

Abstract

Relative permeability curves of water and supercritical (sc) CO2 were obtained for Berea sandstone and Tako sandstone under steady-state flow conditions. The present measurements provide accurate relative permeability values of water and scCO2, which is important to better understand the behavior of CO2 injected into the deep saline aquifer for carrying out carbon dioxide capture and storage (CCS). The mixed fluid of CO2-saturated water and scCO2 was injected into the rock sample that was previously saturated by CO2-saturated water. The flow volumes of the water and scCO2 were measured for different saturation conditions by changing the mixing ratio of the fluids at the sample inlet. The relative permeability curve is then obtained by plotting the relative permeability values with respect to the degree of water saturation estimated by mass balance methods. However, a typical fitting equation (Books and Corey, 1966) cannot adequately approximate relative permeability curves of water-scCO2 systems. Particularly in Tako sandstone, the deviation of measured relative permeability from the calculated relative permeability curve is most likely to be due to sub-core scale heterogeneity due to inhomogeneous pore size distribution.