顶底板岩层透气性对煤层瓦斯抽采的影响研究

Study on the influence of roof and floor rock permeability on gas extraction in coal seam

为了考察煤层顶底板岩性对瓦斯抽采的影响,基于含瓦斯煤流固耦合方程,利用COMSOL Multiphysics软件对透气和不透气2种顶底板岩层进行了钻孔瓦斯抽采数值模拟,其中透气性顶底板岩层孔隙率设置为20%,不透气性顶底板岩层孔隙率设置为0。研究结果表明,不同顶底板岩性条件下在抽采过程中瓦斯总是沿钻孔径向流动,但煤层顶底板岩性对煤层瓦斯流场有明显影响;不同顶底板岩性条件下钻孔瓦斯抽采时间越长,钻孔影响的范围越大,同时距离钻孔中心越远煤层残存瓦斯含量越大,但透气岩层模型的瓦斯压力衰减更快,残存瓦斯压力更低;顶底板岩性对煤层瓦斯抽采有效范围有显著影响,与不透气岩层相比,透气岩层的钻孔有效抽采范围更大。研究结果对穿层钻孔瓦斯抽采具有一定的指导意义。

In order to investigate the influence of roof and floor rock properties on gas drainage,based on the fluid-solid coupling equation of coal containing gas,by using COMSOL multiphysics software,the numerical simulation of gas drainage from drilling for both breathable and impermeable roof and floor strata was carried out,the porosity of the permeable roof and floor rock was set as 20%,and that of the impermeable roof and floor rock was set as 0.The results show that the gas always flows along the drilling in the process of drainage under different roof and floor rock properties,but the roof and floor rock properties have obvious influence on the gas flow field;the longer the gas extraction time under different roof and floor properties,the greater the influence range of drilling,at the same time,the farther away from the center of the drilling,the greater the residual gas content in the coal seam,but the gas pressure of the breathable rock model decreases faster and the residual gas pressure is lower;the roof and floor rock properties have a significant impact on the effective range of coal seam gas drainage,compared with the impermeable rock,the effective range of drilling in the breathable rock is larger.The research results have a certain significance for guiding the gas drainage of drilling passed through coal seam.