考虑启动压力梯度的低渗透煤层瓦斯渗流耦合模型及应用

低透气性煤层瓦斯低速渗流时具有非Darcy渗流的特征,为揭示非Darcy渗流现象的渗流机理,开展了包含非Darcy渗流现象的瓦斯渗流与煤岩变形耦合作用规律研究。根据低透气性煤层瓦斯渗流特征,考虑启动压力梯度作用下的非Darcy渗流规律,研究游离瓦斯渗流、吸附瓦斯扩散流动机理和煤岩变形等过程,建立含启动压力梯度的渗流耦合模型,并利用该模型开展本煤层预抽钻孔数值模拟研究,结果表明,考虑启动压力梯度的模拟结果更符合低渗透煤层瓦斯运移规律,依据模拟结果布置井下钻孔,工作面预抽钻孔抽采瓦斯量为1.09 m3/t,抽采效果理想。

Coupling model of gas seepage in low permeability coal seam considering start-up pressure gradient and its application

The low-velocity gas seepage in low permeability coal seam has the characteristic of non-darcy seepage.In order to reveal the seepage mechanism of non-darcy seepage phenomenon,the coupling law of gas seepage and coal and rock deformation with non-darcy seepage was studied.According to the characteristics of gas seepage in low-permeability coal seam and considering the non-darcy seepage law under the action of starting pressure gradient,the mechanism of free gas seepage,adsorption gas diffusion flow and coal and rock deformation were studied,and the seepage coupling model with starting pressure gradient was established,the model was used to carry out numerical simulation research on the pre-extraction borehole of this coal seam.The results show that the simulation results with considering starting pressure gradient are more consistent with the gas migration law in low-permeability coal seam.According to the simulation results,the borehole was arranged in the underground,and the gas extraction capacity of the pre-extraction borehole in the working face was 1.09 m3/t,the extraction effect was ideal.