Coalbed methane is a hot spot for gas exploration at present, and fractures are widely developed in the coals. However, despite being essential for a number of geophysical applications such as reservoir prediction and hydraulic fracturing, the influence of fractures on the elastic properties and anisotropy of coals is still poorly understood. Therefore, three groups of cylindrical coals were drilled along the face and butt cleat directions to study the effects of pressure and fracture on the elastic properties and anisotropy of tectonic coals. The velocity along the face cleat direction is less sensitive to the pressure than that along the butt cleat direction due to the difference in compliant pore and fracture content. Coals display a strong directional dependence in petrophysical and elastic properties. The permeabilities and velocities of samples along the butt cleat direction are much lower than those along the face cleat direction. The fracture densities are quantitatively characterized by the theoretical model. The values along the face cleat direction are much smaller than those along the butt cleat direction. The influence of fractures on the elastic properties and anisotropy is comprehensively studied by theoretical and laboratory methods. The mineralogy and fracture effects are important factors to the elastic anisotropy of coals, the latter can be a dominant factor to the coal elastic anisotropy. The results can contribute to the understanding of the cleat system of coalbed methane reservoir and can provide a critical rock physics basis for micro‐seismic fracture monitoring and reservoir prediction.

中文翻译：

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构造煤沿面割理方向和底割理方向弹性特性比较

煤层气是当前天然气勘探的热点，煤层裂缝广泛发育。然而，尽管裂缝对于储层预测和水力压裂等许多地球物理应用至关重要，但人们对裂缝对煤的弹性特性和各向异性的影响仍然知之甚少。因此，沿面割理方向钻进三组圆柱形煤，研究压力和破裂对构造煤弹性性质和各向异性的影响。由于顺应性孔隙和裂缝含量的差异，沿面割理方向的速度对压力的敏感度低于沿端割理方向的速度。煤在岩石物理和弹性特性方面表现出强烈的方向依赖性。沿底割理方向的样品渗透率和速度远低于沿面割理方向的渗透率和速度。裂缝密度由理论模型定量表征。沿面割理方向的值远小于沿底割理方向的值。通过理论和实验室方法综合研究了断裂对弹性性能和各向异性的影响。矿物学和断裂效应是影响煤弹性各向异性的重要因素，后者可能是煤弹性各向异性的主导因素。研究结果有助于理解煤层气储层割理系统，为微地震裂缝监测和储层预测提供关键的岩石物理基础。