Non-Darcy properties of gas flow in different metamorphic grade coals
Junwei Yuan 1,2, Gaowei Yue 3
COMPUTER MODELLING & NEW TECHNOLOGIES 2014 18(12A) 578-583
1 College of Safety Science and Engineering, Henan Polytechnic University, No.2001 Road, Jiaozuo, Henan, China
2 State Key Laboratory Cultivation Base for Gas Geology &Gas Control, No.2001 Road, Jiaozuo, Henan, China
3 School of Civil Engineering, Henan Polytechnic University, No.2001 Road, Jiaozuo, Henan, China
Under different confining pressure, gas seepage tests are carried out in different metamorphic grade coals, which tests is used to discuss gas penetration mechanism in coal. The tested and theoretical results show that under different confining pressure, gas seepage laws are consistent in different metamorphic grade coals, but under the same confining pressure and the same gas pressure at the entrance, the metamorphism grade of coal is higher, the gas seepage flow is bigger. In the higher gas pressure section, the percolation curve of Q and Δ2p/L meets the linear relationship, but the gas pressure is lower, the percolation curve of Q and Δ2p/L deviates linear relationship of Darcy's law. The critical point lies from nonlinear to linear segment of gas flow in coal, and it is a gradual process from Non-Darcy flow to Darcy flow. At high Reynolds number, gas percolation obeys Darcy's law, but at low Reynolds number, the gas seepage in different metamorphic grade coals is non-Darcy flow. The collision of gas molecules and coal wall is the physical mechanism of gas non-Darcy flow phenomenon, which is determined by the mean free path of gas molecules and pore structure of coal, and the theoretical calculation well reveals the mechanism of gas non-Darcy seepage in coal.