Experimental Study on Influence of Slippage Effect and Matrix Deformation on Gas Seepage Characteristics of Low Permeability Coal

In order to study the influence of slippage effect and matrix deformation on gas seepage of low permeability coal, based on 8^# coal seam of coal core samples of Yuyang Coal Mine, the gas permeability of coal samples is studied by using four kinds of gas. The results show that: when axle loading, confining pressure and gas pressure is constant, the permeability induced by slippage effect shows △K_He，b＞△K_CH4，b＞△K_N2，b＞△K_CO2，b, and the permeability induced by matrix deformation shows that the stronger adsorbability will cause bigger matrix deformation under the same gas pressure level, namely, △K_He，s＜△K_N2，s＜△K_CH4，s＜△K_CO2，s; the permeability induced by slippage effect (△K_i,b), the permeability induced by matrix deformation (△K_i,s) and the effective permeability (△K_i,g) all represent the nonlinear change with the increase of gas pressure under fixed axial and confining pressure. The relationship between the permeability induced by slippage effect (△K_i,b) and gas pressure can be expressed as △K_i，b=ap^b，and the relationship between the permeability induced by matrix deformation (△K_i,s) and gas pressure can be expressed as △K_i，s=ap²+bp +c，and the relationship between the effective permeability (△K_i,g) and gas pressure can be expressed as △K_i，g=ap^b+bp +c.