基于非理想气体流动模拟的无烟煤纳米孔隙中CH₄流动规律

Based on the nanoscale pore-network flow model (PNFM) of anthracite coal collected from the southern Qinshui Basin, a non-ideal gas-flow simulation of CH₄ was carried out considering slip flow, diffusion, gas desorption/adsorption and Darcy flow. The apparent permeability of nanopores in anthracite coal and the microscopic flow behavior of CH₄ were discussed. The results show that the non-ideal gas-flow model quantifies the effects of slip flow, diffusion and gas properties on apparent permeability. The apparent permeability of nanopores in anthracite coal is greater than the Darcy permeability affected by slip flow and diffusion of CH₄. The apparent permeability exhibits negative exponential relationships with the tangential momentum accommodation coefficient (β), gas pressure, and pore width. Knudsen number has a nonlinear increasing trend with the decrease in gas pressure and pore width, causing a nonlinear relationship between apparent permeability and gas pressure. Moreover, the slip coefficient increases with the decrease in the β and gas pressure. When β<0.1 and gas pressure ≤8 MPa, the effects of slip flow and diffusion on CH₄ migration in mesopores and macropores with a width of 50-100 nm increases rapidly, which is crucial for the efficiency of CH₄ production and CBM exploitation.