Gas-water relative permeability measurement of high temperature and high pressure tight gas reservoirs

Generally, gas-water relative permeability curves of tight gas reservoirs are obtained from unsteady experiment under room temperature and normal pressure, which greatly differs from the curves under high temperature and high pressure. In this research, the relative permeability curves of three cores were firstly measured using conventional standard method by displacing formation water with nitrogen under room temperature and normal pressure. Then the relative permeability curves of the same cores were measured by displacing formation water with natural gas on one self-developed full-diameter seepage flow equipment (200 °C, 200 MPa) under reservoir conditions (160 °C, 116 MPa) after several processing of the cores. Difference between the relative permeability curves obtained by the two methods shows that, under high temperature and high pressure, there exists a larger two-phase seepage zone and lower irreducible water saturation. At the same gas saturation, gas relative permeability under high temperature and high pressure is higher than that under room temperature and normal pressure, which means, under reservoir situation, the two-phase flow ability of gas and water is stronger and the irreducible water saturation is lower in tight gas reservoirs. The gas-water viscosity ratio, gas-water density ratio and interfacial tension are lower under this situation, which leads to higher sweep efficiency.