Pore throat structure and flow characteristics of sandstone reservoirs

Mercury injection testing, gas-water relative permeability testing and physical simulation experiments of gas reservoir depletion were carried out with cores from the Xujiahe Formation in the Sichuan Basin (permeability: 0.002-70.28 mD). The differences between tight sand gas reservoirs and high permeability gas reservoirs of the pore structure characteristics, force characteristics and gas-water relative permeability characteristics were analyzed. The approach was as follows: (1) The pore structure characteristics of sandstones with different permeability were described by three parameters: pore throat ratio, average throat radius and median throat radius, and the pore structure characteristic differences between tight sand gas reservoirs and high permeability gas reservoirs were comparatively analyzed. (2) The force situations of gas and water flowing in the sandstones with different permeability were quantitatively evaluated by threshold pressure and frictional drag, and the impacts of pore structure on the capacities of tight sand gas reservoirs and high permeability gas reservoirs were analyzed. (3) The relation diagram of gas relative permeability and water saturation were derived, and the impact of water saturation on the gas relative permeability of cores with different permeability was analyzed. The research results will provide a reference for gas reservoir microcosmic modeling and the study of gas and water percolation mechanism.