Determination of stress dependent relative permeability of low permeable rocks injected with supercritical CO2

摘要

In this paper, we propose a numerical approach to determine CO2-water relative permeability from the experimental test of the injection of supercritical CO2 into low permeable rock. The theoretical analysis was modified in order to incorporate two phase drainage displacement while poroelastic geomechanical analysis was employed to quantify the stress-strain as well as the porosity-permeability that altered during the injection. The applicability of the numerical analysis was examined in the injection of supercritical CO2 with 3 ??l/min flow rate into a cored Ainoura sandstone saturated by water within initial condition of 10 MPa pore pressure, 20 MPa confining pressure, and 35??C temperature. During injection, the hydraulic pressures in the upstream and downstream of the core including its longitudinal and lateral strains were measured. The experimental results showed that CO2 injection generates an increase in hydraulic pressure across the core up to 16.93 MPa, and the increase in volumetric strain by 0.7%. As a consequence, porosity and permeability changes by a factor of 1.22 and 2.03 of those initial values were observed, respectively. It was also found that CO2 and water relative permeability values yielded lower values by 25% and 65%, respectively, when geomechanical effects on the hydraulic behavior are considered . The results suggest that the determination of relative permeability by core scale measurement needs to accommodate both hydraulic and geomechanical effects, especially in case of low permeable rocks.