Coal seams are usually fractured reservoirs where the factures/cleats are fluids flow channels, and the matrix blocks serve as the storage space. The gas transport within the matrix has crucial impacts on the variation of cleat aperture and thus affects the reliable determination of coal permeability. Most literature on laboratory measurements and the development of relevant analytical models focus on response gas pressure dependent coal permeability change, under the assumption that gas transport in coal is in equilibrium. This means that these models are not suitable for the assessment of transient permeability when gas transport in coal is unsteady flow. In this paper, we real-time measured the entire process of the coal deformation induced by gas injection, and further obtained the diffusion-dependent curve of coal permeability against time by modifying the typical pressure-pulse-decay approach. An improved permeability model was then proposed by incorporating an Internal Deformation Coefficient into the pore compressibility of coal seams. The results show that the gas inflow can decline the pressure differential between the downstream pressure and the upstream pressure, during which the deformation of coal experiences a transition from early rapid expansion to latter slow expansion. As the gas was diffusing into coal matrices, the coal permeability was observed to first decrease and then became stable. It is also found that Internal Deformation Coefficient increases with the injection gas pressure. This indicates that the matrix blocks preferentially swell toward cleats. The modified permeability model achieves a much better fit of the coal permeability-pore pressure relationship when compared with two widely used permeability models. This approach can be extended to evaluate the deformation compatibility between coal cleats and matrices.

煤层通常是裂缝性储层，其中的裂缝/夹缝是流体的流动通道，而基质块则作为储藏空间。基质内的气体传输对防滑钉孔径的变化具有至关重要的影响，因此影响了煤渗透率的可靠确定。假设煤中的气体运输处于平衡状态，大多数关于实验室测量和相关分析模型发展的文献都集中在响应气体压力相关的煤渗透率变化上。这意味着当煤中的气体输送为非稳定流动时，这些模型不适合评估瞬态渗透率。在本文中，我们实时测量了注气引起的煤变形的全过程，并通过修改典型的压力-脉冲-衰减方法获得了煤渗透率随时间的扩散相关曲线。然后通过合并一个内部变形系数转化为煤层的孔隙可压缩性。结果表明，瓦斯涌入可以减小下游压力与上游压力之间的压力差，在此期间，煤的变形经历了从早期快速膨胀到后期缓慢膨胀的转变。随着气体扩散到煤基质中，观察到煤的渗透率先降低然后稳定。还发现内部变形系数随着注入气体压力的增加而增加。这表明矩阵块优先向防滑钉膨胀。与两个广泛使用的渗透率模型相比，改进的渗透率模型可以更好地拟合煤的渗透率-孔隙压力关系。这种方法可以扩展到评估煤夹板与基体之间的变形相容性。