Coal seam contains a large number of fractures, whose shape and structure of fissures are complicated, and they are the main channels for gas migration. Therefore, the quantitative analysis of the internal relationship between the microstructure and the macroscopic permeability is the key issue to increase the drainage volume. Some investigators discussed the permeability of coal seams based on the fractal theory, but the mechanisms of gas migration under the influence of fissure microstructures and coal deformation are still unclear. Moreover, most of the multi-process coupling analysis in the stage of Coal Bed Methane (CBM) mining was not taken into account. In this paper, the effects of fissure structures on the coal gas drainage rate in multi-field coupling are studied. Aiming at the mechanisms of gas drainage under the joint action of fracture structure, in-situ stress and adsorption deformation, we propose a two-scale multi-field coupling model, which takes into account the influences of micro fracture and pore structure. On this basis, we obtained the pressure evolution rule of coal seam pore system and fissure system and the distribution rule of coal seam displacement with drilling positions. Meanwhile, the effects of coal seam maximum fracture length, maximum pore diameter, the fractal dimension for fractures and fractal dimension for pores on coal seam extraction are discussed.

中文翻译：

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考虑裂缝-孔隙微观结构与煤体变形耦合过程的瓦斯抽采研究

煤层含有大量裂缝，裂缝形态结构复杂，是瓦斯运移的主要通道。因此，定量分析微观结构与宏观渗透率的内在关系是提高泄油量的关键。一些研究者基于分形理论讨论了煤层的渗透率，但在裂隙微观结构和煤变形影响下的瓦斯运移机制尚不清楚。此外，大部分煤层气（CBM）开采阶段的多过程耦合分析没有考虑在内。本文研究了裂隙结构对多场耦合下瓦斯抽采率的影响。针对裂缝结构、地应力和吸附变形共同作用下的瓦斯抽放机理，提出了考虑微裂缝和孔隙结构影响的两尺度多场耦合模型。在此基础上，得到了煤层孔隙系统和裂隙系统的压力演化规律以及煤层位移随钻位分布规律。同时，讨论了煤层最大裂缝长度、最大孔径、裂缝分形维数和孔隙分形维数对煤层开采的影响。得到了煤层孔隙系统和裂隙系统的压力演化规律以及煤层位移随钻井位置的分布规律。同时，讨论了煤层最大裂缝长度、最大孔径、裂缝分形维数和孔隙分形维数对煤层开采的影响。得到了煤层孔隙系统和裂隙系统的压力演化规律以及煤层位移随钻井位置的分布规律。同时，讨论了煤层最大裂缝长度、最大孔径、裂缝分形维数和孔隙分形维数对煤层开采的影响。