Effect of moisture content on CBM seepage

The moisture content determines CBM occurrence state and its transport capacity in coal seam. Based on the substrate adsorption deformation theory, the authors analyzed the effects of water content on the mechanical properties of matrix, and moisture content control on fracture deformation and coal-bed gas migration in coal seam, and completed a group of CBM seepage experiments using coal samples with different moisture contents, 0.112%, 0.498% and 0.785% respectively. The study demonstrates that the seepage velocity nonlinearly decreases with the increase of effective stress in the stress loading process; the flow velocity and effective stress relationship is a quadratic function of distribution; and the moisture content determines the stress sensitive area and the minimum flow velocity. Therefore, the maximum flow rate can be calculated. With the increase of water content, the stress sensitive point of CBM seepage velocity decreases gradually, i.e., 5.48, 5.17 and 4.78 MPa.