Abstract
For CO(2) enhanced CH(4) recovery in the coal seam, whose effective permeability would change with the different phase CO(2). To evaluate this, a steady-state seepage test method was used to conduct the permeability tests under varying multiphase and multi-component CO(2)/CH(4) mixture fluid. The mixture permeability of gaseous or supercritical CO(2) + CH(4) under different fractions decreases with respect to the CO(2) concentration increasing. Meanwhile, the mixture permeability first decreases and then increases with the increasing injection pressure, and there is an obvious slippage effect when the injection pressure is lower than 3 MPa. The established permeability model values are in good agreement with the experimental data. The coal deformation accords with the Langmuir equation in the seepage process of CO(2) + CH(4) mixture under in situ conditions, and the two equation parameters (ε(L), P (L)) have a good linear relationship with CO(2) concentration. The CH(4) concentration in the outlet increases about 24.5% in the supercritical CO(2) + CH(4) mixture but less dramatic only about 8.5% in the gaseous CO(2) + CH(4) mixture. At the same time, the gaseous CO(2) (or CH(4)) effective permeability increases (decreases) with increasing gaseous CO(2) concentration, while the supercritical CO(2) or CH(4) effective permeability basically remains unchanged with increasing supercritical CO(2) concentration. This study is meaningful for the prediction of mixed fluid permeability in the process of the CO(2) displacement exploitation of CH(4).