Abstract The cleat or natural fracture system is a dominant factor controlling the permeability of coal seams. Gas permeability and porosity of coal samples with artificially generated fractures are measured under varying effective stress. Based on the experimental results and the Walsh model, fracture width and roughness are estimated. Considering the fracture aperture and roughness, we present a 3D geometry model to reconstruct coal fracture networks on the basis of the Voronoi tessellations. The lattice Boltzmann method (LBM) is applied to simulate fracture flows and to predict the associated permeability. For comparison purposes, simulations in a single fracture are carried out initially. For a single smooth fracture, the results of LBM simulations show a good agreement with the cubic law. For a single rough fracture, the cubic law overestimates the permeability, and it is two to four orders of magnitude higher than the laboratory measurement. The predicted permeability by LBM simulation is in acceptable agreement with laboratory measurement. Furthermore, the flows through the fracture networks with smooth fracture surfaces are simulated. By comparison to the matchstick model, simulation errors are mostly within 30%. Finally, the effects of structure, surface roughness and aperture on flows in fracture networks with rough fracture surfaces are investigated. The present study provides a promising approach to predict the associated permeability and transport characteristics in coal fracture networks.

中文翻译：

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煤裂缝网络中气体流动和渗透率预测的格子 Boltzmann 模拟

摘要 割理或天然裂缝系统是控制煤层渗透率的主导因素。在不同的有效应力下测量具有人工产生裂缝的煤样的气体渗透率和孔隙度。根据实验结果和沃尔什模型，估计裂缝宽度和粗糙度。考虑到裂缝孔径和粗糙度，我们提出了一个 3D 几何模型来重建基于 Voronoi 镶嵌的煤裂缝网络。格子 Boltzmann 方法 (LBM) 用于模拟裂缝流动并预测相关的渗透率。出于比较的目的，最初在单个裂缝中进行模拟。对于单个光滑裂缝，LBM 模拟的结果与三次定律非常吻合。对于单个粗糙断裂，三次定律高估了渗透率，比实验室测量高出两到四个数量级。LBM 模拟预测的渗透率与实验室测量结果一致。此外，模拟通过具有光滑断裂面的断裂网络的流动。与火柴棒模型相比，仿真误差大多在 30% 以内。最后，研究了结构、表面粗糙度和孔径对具有粗糙裂缝表面的裂缝网络中流动的影响。本研究为预测​​煤裂隙网络中相关的渗透率和输运特征提供了一种很有前景的方法。LBM 模拟预测的渗透率与实验室测量结果一致。此外，模拟通过具有光滑断裂面的断裂网络的流动。与火柴棍模型相比，仿真误差大多在 30% 以内。最后，研究了结构、表面粗糙度和孔径对具有粗糙裂缝表面的裂缝网络中流动的影响。本研究为预测​​煤裂隙网络中相关的渗透率和输运特征提供了一种很有前景的方法。LBM 模拟预测的渗透率与实验室测量结果一致。此外，模拟通过具有光滑断裂面的断裂网络的流动。与火柴棍模型相比，仿真误差大多在 30% 以内。最后，研究了结构、表面粗糙度和孔径对具有粗糙裂缝表面的裂缝网络中流动的影响。本研究为预测​​煤裂隙网络中相关的渗透率和输运特征提供了一种很有前景的方法。研究了具有粗糙断裂表面的断裂网络中流动的表面粗糙度和孔径。本研究为预测​​煤裂隙网络中相关的渗透率和输运特征提供了一种很有前景的方法。研究了具有粗糙断裂表面的断裂网络中流动的表面粗糙度和孔径。本研究为预测​​煤裂隙网络中相关的渗透率和输运特征提供了一种很有前景的方法。