煤层钻孔有效抽采半径数值模拟研究

Study on numerical simulation of effective drainage radius of drilling hole in coal seam

在煤层瓦斯流动理论和弹性力学基础上,考虑煤体渗透率变化对瓦斯流动的影响,建立了含瓦斯煤岩渗流-应力耦合数学模型,根据该模型对COMSOL Multiphysics数值模拟软件进行二次开发,以某突出矿井为例建立了煤层钻孔瓦斯抽采模型,并进行求解计算,结果表明煤层瓦斯压力、煤体渗透率均随抽采时间的增加而逐渐降低,钻孔有效抽采半径随抽采时间的增加而逐渐扩大,但均具有一定的时效性;采用压力法进行现场测试,实测结果与模拟结果基本一致,证明了含瓦斯煤岩渗流-应力耦合数学模型的正确性及采用数值模拟方法计算煤层钻孔有效抽采半径的可行性。

A seepage-stress coupling model of coal containing gas was established considering effect of coal permeability changing on gas flow based on coal seam gas flow theory and elastic mechanic.Thesecond development of COMSOL Multiphysics numerical simulation software was taken according to the model.A model of gas drainage model of drilling hole in coal seam was established taking agas outburst mine as an example and resolved with numerical solution.The results show that coal seam gas pressure and coal permeability decrease gradurally with time extending,meanwhile effective radius of drilling hole increases gradually,and both have certain timeliness.The field test is taken by use of a pressure testing method with a result in accordance with the simulated one basically,which verifies correctness of the seepage-stress coupling model of coal containing gas and feasibility of calculating effective drainage radius of drilling hole by numerical simulation method.