Quantitative characterization of shale gas flow in fractured shale is a key problem in shale gas extraction. In this study, 3D multi-scale structures in fractured shale were reconstructed, firstly, by X-ray micro-computerized tomography (CT), high-resolution scanning electron microscope (SEM), and fractal function. Then, a REV (representative elementary volume)-scale lattice Boltzmann (LB) model, considering Klinkenberg’s effect and gas absorption, was built, and the effects of fracture complexity and gas pressure on shale gas flow and shale permeability were analyzed and studied quantitatively. The simulation results indicate that the gas flow behaviors in the fractured shale are related strongly to fracture morphology and gas pressure. The decreased fracture fractal dimension or increased complexity of the fracture network leads to increase in permeability of the fractured shale. The gas velocity in the shale matrix decreases with increasing fracture roughness. Increased fracture network connectivity contributes to the formation of local high-intensity velocity fields and the improvement of gas flow in the shale matrix. The gas rarefaction effect has a significant influence on gas flow in the fractured shale, and permeability of the fractured shale must be regarded as a dynamic shale reservoir parameter. The gas flow behavior in the fractured shale is more sensitive at low-pressure condition whereas the gas rarefaction effect is more sensitive to the fractured shale with highly rough fracture or low fracture connectivity.

压裂页岩中页岩气流动的定量表征是页岩气提取中的关键问题。在这项研究中，首先通过X射线计算机断层扫描（CT），高分辨率扫描电子显微镜（SEM）和分形函数重建了裂缝性页岩中的3D多尺度结构。然后，建立了考虑克林根贝格效应和气体吸收的REV（代表基本体积）尺度晶格玻尔兹曼（LB）模型，并定量分析和研究了裂缝复杂度和气压对页岩气流量和页岩渗透率的影响。模拟结果表明，裂缝页岩中的气体流动行为与裂缝形态和气压密切相关。减小的裂缝分形维数或增加裂缝网络的复杂性会导致裂缝性页岩的渗透率增加。页岩基质中的气体速度随着裂缝粗糙度的增加而降低。裂缝网络连通性的提高有助于形成局部高强度速度场，并改善了页岩基质中的气流。气体稀疏效应对裂缝性页岩中的气体流动有显着影响，必须将裂缝性页岩的渗透率视为动态的页岩储层参数。在低压条件下，裂隙页岩中的气体流动行为更为敏感，而裂隙页岩的瓦斯稀疏效应对裂隙程度较高或裂缝连通性较低的裂隙页岩更敏感。页岩基质中的气体速度随着裂缝粗糙度的增加而降低。裂缝网络连通性的提高有助于形成局部高强度速度场，并改善了页岩基质中的气流。气体稀疏效应对裂缝性页岩中的气体流动有显着影响，必须将裂缝性页岩的渗透率视为动态的页岩储层参数。在低压条件下，裂隙页岩中的气体流动行为更为敏感，而裂隙页岩的瓦斯稀疏效应对裂隙程度较高或裂缝连通性较低的裂隙页岩更敏感。页岩基质中的气体速度随着裂缝粗糙度的增加而降低。裂缝网络连通性的提高有助于形成局部高强度速度场，并改善了页岩基质中的气流。气体稀疏效应对裂缝性页岩中的气体流动有显着影响，必须将裂缝性页岩的渗透率视为动态的页岩储层参数。在低压条件下，裂隙页岩中的气体流动行为更为敏感，而裂隙页岩的瓦斯稀疏效应对裂隙程度较高或裂缝连通性较低的裂隙页岩更敏感。裂缝网络连通性的提高有助于形成局部高强度速度场，并改善了页岩基质中的气流。气体稀疏效应对裂缝性页岩中的气体流动有显着影响，必须将裂缝性页岩的渗透率视为动态的页岩储层参数。在低压条件下，裂隙页岩中的气体流动行为更为敏感，而裂隙页岩的瓦斯稀疏效应对裂隙程度较高或裂缝连通性较低的裂隙页岩更敏感。裂缝网络连通性的提高有助于形成局部高强度速度场，并改善了页岩基质中的气流。气体稀疏效应对裂缝性页岩中的气体流动有显着影响，必须将裂缝性页岩的渗透率视为动态的页岩储层参数。在低压条件下，裂隙页岩中的气体流动行为更为敏感，而裂隙页岩的瓦斯稀疏效应对裂隙程度较高或裂缝连通性较低的裂隙页岩更敏感。