An improved experimental procedure and mathematical model for determining gas-water relative permeability in tight sandstone gas reservoirs

The gas-water relative permeabilities (GWRPs) of five rock samples were determined under different pore pressures to analyze and model the effects of pore pressure and rock-sample permeability in tight sandstone gas reservoirs. The gas-water permeability curves measured at 10-30 MPa are higher than those at normal pressure, and the co-permeability interval is narrower. At the same water saturation, the relative permeabilities of gas and water decrease with increasing pore pressure, especially that of gas. Under the same pore pressure conditions, with decreasing absolute permeability, gas-water relative permeability decreases, with the difference becoming smaller with increasing pore pressure. Finally, the experimental data for four rock samples was subjected to multiple linear fitting using Origin software, and a mathematical model of gas-water relative permeability was established. The accuracy and applicability of the mathematical model were verified by comparing the gas-water permeability curve calculated by the mathematical model with the experimental results for the fifth rock sample. Our findings provide invaluable information regarding gas-water two-phase seepage during the development of tight sandstone gas reservoirs and make predicting their productivities and production performances more accurate.