A novel method for simultaneous determination of relative permeability and capillary pressure from corefloods (gas/CO2–water systems)

Abstract

Enhanced oil recovery (EOR) using CO2 injection is being investigated as a feasible technique for oil reservoirs. The ability of a reservoir to store CO2 for a long time presents an opportunity to create sustainable solutions to the problems posed by the continued use of fossil fuels and climate change, and to support the commitment to regional, national, and global agreements to reduce CO2 emissions. Injection strategies such as water-alternate-gas (WAG) or carbonised water injection (CWI) have been proposed to overcome the issue of low sweep efficiency of CO2 flood in the reservoir. An understanding of the relative permeability and capillary pressure behaviour is necessary to simulate these processes in porous media. The steady-state coreflood test is a widely accepted industrial method to determine relative permeability (Kr), but the capillary pressure (Pc) must be found from other sources (porous plate, mercury injection, and centrifuge tests). A significant difference between the capillary pressure determined from corefloods and by other methods is widely presented in the literature. This work presents a novel coreflood method for the simultaneous determination of relative permeability (Kr) and capillary pressure (Pc). The main idea is to use the stabilised data of the steady-state method along with the transient data of the pressure drop. Therefore, in the proposed steady-state-transient test (SSTT), the transient pressure drop data across the core, between the sequential steady-states, are used instead of the traditionally utilised Pc-curve.