Effect of Confining Pressure on CO₂-Brine Relative Permeability Characteristics of Sandstone in Ordos Basin

CO₂-brine relative permeability significantly impacts CO₂ injection and is a key parameter for carbon dioxide storage simulation in saline aquifers. In the study of relative permeability, factors such as temperature, pressure, and reservoir rock physical properties play a crucial role. To better understand the impact of confining pressure on the CO₂-brine relative permeability characteristics of sandstone in the Ordos Basin, five sets of CO₂-brine relative permeability data were obtained through unsteady-state displacement tests conducted at various confining pressures ranging from 12 to 20 MPa. The research findings indicate that with an increase in confining pressure there is a slight decrease in irreducible brine saturation. Furthermore, the CO₂ relative permeability in the irreducible brine state decreased by 57% as the pressure increased from 12 MPa to 20 MPa. The study demonstrates notable differences in the CO₂-brine relative permeability curves under varying confining pressure conditions. As the confining pressure increases, the CO₂ relative permeability curve decreases, while the brine relative permeability increases. The change in brine relative permeability is not as pronounced as that of CO₂. These experimental results offer essential support for subsequent numerical calculations and practical applications in engineering. Experimental research holds significant importance in the assessment of storage potential and the prediction of the evolutionary patterns of CO₂ migration.