Sun Hao, Fan Chaojun, Yang Lei, Luo Mingkun, Xiao Bin, Wang Lei, Zhou Lijun
College of Mining, Liaoning Technical University, Fuxin, 123000, China.
Ventilation Department of Energy Business Department, Shanxi Lu'an Chemical Group Co., Ltd, Changzhi, 046200, China.
Sci Rep. 2024 Oct 15;14(1):24155. doi: 10.1038/s41598-024-74259-x.
The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick's law, Darcy's law, the ideal gas law and the Langmuir equation, a damage-seepage-deformation coupling mathematical model of CSW fracturing in coal seam combined with the maximum tensile stress and the Mohr-Coulomb criterion is established. This model is implemented into COMSOL Multiphysics to simulate the coal seam CSW fracturing and subsequent gas extraction. When the shock wave and isotropic in-situ stress are applied on the borehole wall, the coal damage zone is an annular shape, and the permeability in the damage zone increases sharply. The CSW can effectively increase the efficiency of gas extraction and reduce the gas pressure and gas content in coal seam. With the increase of CSW action times, the damage in coal mass reaches a threshold and tends to be stable after several shocks. The damage area and the gas extraction efficiency are positively correlated with the shock intensity. Under the anisotropic ground stress, the larger diversity of the stress in different directions is, the more obvious damage extension in the fractured coal along the maximum stress direction is. Ground stress can inhibit the extension of cracks in the CSW fractured coal seam. This inhibition effect becomes more obvious with the increase of in-situ stress. Parameters are substantiated of controlled shock wave impact on the coal seam, which ensures increased methane extraction from low-permeability reservoirs, are substantiated.
可控冲击波（CSW）压裂是提高煤层渗透率以促进瓦斯抽采的有效方法。基于菲克定律、达西定律、理想气体定律和朗缪尔方程，结合最大拉应力和莫尔-库仑准则，建立了煤层CSW压裂损伤-渗流-变形耦合数学模型。将该模型应用于COMSOL Multiphysics软件中，模拟煤层CSW压裂及后续瓦斯抽采过程。当冲击波和各向同性地应力作用于钻孔壁时，煤体损伤区呈环形，损伤区内渗透率急剧增加。CSW能有效提高瓦斯抽采效率，降低煤层瓦斯压力和瓦斯含量。随着CSW作用次数的增加，煤体损伤达到阈值，经过几次冲击后趋于稳定。损伤面积和瓦斯抽采效率与冲击强度呈正相关。在各向异性地应力作用下，不同方向应力差异越大，裂隙煤体沿最大应力方向的损伤扩展越明显。地应力会抑制CSW压裂煤层中裂纹的扩展，且随着地应力的增加，这种抑制作用更加明显。证实了可控冲击波对煤层的影响参数，这些参数确保了从低渗透储层中提高甲烷抽采量。
