The drainage and utilization of coalbed methane (CBM) resources can not only ensure the safe production of coal mines but also can reduce greenhouse gas emissions and protect the environment. Coal permeability is the key factor that affects the CBM drainage efficiency. To understand the coal permeability evolution characteristics, coal specimens reconstituted by coal powder with different particle sizes were prepared and their permeability under loading conditions was investigated. The results indicate that the coal permeability evolution laws measured by different gases are completely different under constant hydrostatic pressure conditions due to the influence of effective stress and the coal matrix sorption‐induced deformation. Under constant effective stress conditions, the helium permeability of coals is almost unchanged if the effects of the Biot's coefficient of coals are ignored, but the methane permeability of coals decreases with increasing gas pressure. In the complete stress–strain process, the variation of coal permeability as the axial strain increases at different stages is almost completely different and the coal permeability in the residual plastic flow stage increases by 2.4–71 times, 1.5–39 times, and 2.8–116 times that of the initial state under the different boundary conditions. Furthermore, it is also found that the coal permeability evolution laws are determined by the effective stress, the sorption‐induced deformation of coal matrices, and the malconformation of gas adsorption in coals. This study can help us better understand the seepage characteristics of gas in coals and guide the CBM development. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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煤渗透性演化特征：不同加载条件下的分析

煤层气资源的排放和利用，不仅可以保证煤矿的安全生产，还可以减少温室气体的排放，保护环境。煤的渗透性是影响煤层气排采效率的关键因素。为了了解煤的渗透性演化特征，准备了用不同粒径的煤粉重构的煤样品，并研究了其在加载条件下的渗透性。结果表明，由于有效应力和煤基质吸附诱导变形的影响，在恒定静水压条件下，不同气体测得的煤渗透率演化规律完全不同。在恒定的有效应力条件下，如果忽略了煤的毕奥特系数的影响，则煤的氦渗透率几乎不变，但是煤的甲烷渗透率随气压的增加而降低。在完整的应力应变过程中，煤渗透率随轴向应变的增加而在不同阶段几乎完全不同，剩余塑性流动阶段的煤渗透率分别增加了2.4-71倍，1.5-39倍和2.8-。不同边界条件下初始状态的116倍。此外，还发现煤的渗透率演化规律是由有效应力，煤基质的吸附诱导变形以及煤中气体吸附的畸形决定的。这项研究可以帮助我们更好地了解煤中瓦斯的渗流特征，并指导煤层气的开发。©2020年化学工业协会和John Wiley＆Sons，Ltd.