低渗煤层水力割缝钻孔抽采影响半径

Influence radius of hydraulic slotted hole drainage in low permeability coal seam

为了研究低透气性煤层超高压水力割缝钻孔瓦斯抽采半径的影响因素,以彬长矿区孟村矿401102工作面4#低渗煤层为研究对象,通过理论分析建立超高压水力割缝钻孔的裂隙扩展-渗流模型,分析水力割缝钻孔塑性区宽度及高压水的渗流范围。采用COMSOL Multiphysics多场耦合软件进行数值模拟,选取割缝半径、抽采时间、瓦斯压力、渗透率作为主要影响因素,分析不同影响因素条件下瓦斯抽采半径的变化规律,并进行现场测试试验,检验数值模拟的合理性。结果表明:水力割缝钻孔的瓦斯抽采影响范围主要为四周煤体破裂产生的次生裂隙及高压水经过次生裂隙渗流的影响范围;割缝半径、渗透率、抽采时间、瓦斯压力的变化对瓦斯抽采半径有显著影响,且随着影响因素逐渐增大,瓦斯抽采半径均呈现逐渐增大的趋势;割缝钻孔瓦斯抽采半径与各影响因素之间均呈现一种对数函数的关系;通过现场测试超高压水力割缝瓦斯抽采影响半径约为4~5 m,与数值模拟的结论基本保持一致。

In order to study the influence factors of gas drainage influence radius under high pressure hydraulic slotting in low permeability coal seam,the 4#low permeability coal seam of 401102 working face in Mengcun mine of Binchang mining area is taken as a research object.A fracture expansion-seepage model of ultra-high pressure hydraulic slotting boreholes was established,with the width of plastic zone and seepage range of high pressure water examined.Meanwhile,COMSOL Multiphysics multi-field coupling software was adopted for numerical simulation.The main influencing factors selected are slotting radius,extraction time,gas pressure and permeability.Then the variation of gas drainage radius under different influencing factors was analyzed.At the same time,the rationality of numerical simulation was verified by field test.The results indicate that the gas drainage in hydraulic slotting boreholes mainly influences the secondary cracks of surrounding coal seams and high-pressure water seepage range through secondary cracks.The radius of gas drainage enlarges gradually with the influencing factors becoming stronger.There is also a logarithmic function relationship between the drainage radius and the influencing factors mentioned above.The field test suggests that the influence radius of ultra-high pressure hydraulic slotting seam gas drainage is about 4~5 m,which is basically consistent with the conclusion of numerical simulation.