ANALYSIS OF PRESSURE-DEPENDENT RELATIVE PERMEABILITY IN PERMEABILITY JAIL OF TIGHT GAS RESERVOIRS AND ITS INFLUENCE ON TIGHT GAS PRODUCTION

摘要

This paper develops a model for pressure-dependent relative permeability in the presence of permeability jail and analyzes its influence on tight gas production. The model for pressure-dependent relative permeability is derived by introducing a pressure calibration coefficient into the modified Corey equation to describe the influence of pressure on gas flow capability in tight gas reservoirs. The model is validated using experimental data of tight sandstones and is compared with the conventional model. Pressure sensitivity of gas relative permeability is analyzed. Tight gas production affected by pressure-dependent relative permeability is also studied. Results demonstrate that the decrease of pressure can induce the increase of gas relative permeability. The effect of pressure is significant when pressure is low. However, under reservoir condition, when reservoir pressure falls, gas production decreases although gas relative permeability rises because the reduction of reservoir pressure leads to a decreasing pressure drop between reservoir pressure and bottomhole pressure, which has a more significant influence on tight gas production than the effect caused by the rise of gas relative permeability.