考虑各向异性影响的煤层吸附及渗透机制研究

为探究煤层各向异性渗流机制,分析其吸附特性,建立吸附模型并计算吸附变形量,进而量化吸附作用对渗透率的贡献情况。在此基础上分析煤层各向异性渗流特性,进一步构建应力和滑脱效应耦合作用的各向异性渗透率模型,并通过试验数据验证其适用性。结果表明:煤层瓦斯吸附过程受吸附变形和外应力的影响,且不同方向的瓦斯吸附量存在差异;在孔隙压力增大过程中,各方向瓦斯吸附量曲线先增大后趋于平缓;在有效应力、孔隙压力和滑脱效应的综合作用下,煤层各方向的渗透率均先减小后趋于平缓。考虑应力和滑脱效应耦合作用下煤层各向异性渗透率模型计算曲线与试验值吻合度较高,验证了模型的适用性。

Research on adsorption and permeability mechanism of coal seams considering influence of anisotropy

In order to explore the anisotropic seepage mechanism of coal seams,an adsorption model was established by analyzing its adsorption characteristics and the amount of adsorption deformation was calculated.Furthermore,the contribution of adsorption to permeability was quantified.On this basis,the anisotropic seepage characteristics of coal seams were analyzed.An anisotropic permeability model with coupling effect of stress and slippage effect was further constructed,and its applicability was verified by experimental data.The results show that the coal seam gas adsorption process is affected by sorption・induced deformation and external stress and there are differences in gas absorption amount in different directions,that during the increase of pore pressure,the gas adsorption curve in each direction shows a trend of increasing first and then flattening out,that under the combined effect of effective stress,pore pressure and slippage effect,the permeability of coal seams in all directions shows a decreasing trend and then a gentle change,and that considering the coupling effect of stress and slippage,the calculated curve of the anisotropic permeability model of the coal seam is in good agreement with the experimental value,which verifies the applicability of the model.