基于孔-裂隙的煤层瓦斯抽采热-流-固耦合模型研究

Thermal-hydrological-solid coupling model of coal seam gas extraction based on pore-fracture

为研究温度因素对负压钻孔抽采瓦斯的影响,建立了基于孔-裂隙双重多孔介质的热-流-固耦合模型,运用数值模拟手段,对比了不考虑温度因素下基于气-固耦合模型的瓦斯抽采特点和抽采效果。模拟结果表明:考虑温度因素影响所得渗透率结果更小,抽采卸压效果相对较弱;初始煤层瓦斯压力越高,煤层温度降低越明显;考虑温度变化影响,针对不同有效抽采半径R,进行了孔间距为2√3 R/3、2R、4R、6R的多钻孔布孔研究,得出有效抽采区域随抽采时间增加呈现由多个小圆柱状发展为一个大圆角三棱柱,最后趋向于一个规则的大圆柱状的变化规律。研究成果可为预抽煤层瓦斯前布孔设计工作及实际瓦斯灾害防控提供一定的参考。

In order to study the influence of temperature factors on gas extraction by negative pressure drilling,a thermal-fluid-solid coupling model based on pore-fracture dual porous media was established.By means of numerical simulation,the gas extraction characteristics and extraction effect based on gas-solid coupling model without considering temperature factors were compared.The simulation results show that the permeability results obtained by considering the influence of temperature factors are smaller,and the effect of pressure relief is relatively weak.The higher the initial coal seam gas pressure is,the more obvious the coal seam temperature decreases.Considering the influence of temperature change,for different effective extraction radius R,the multi-hole spacing of 2√3 R/3,2R,4R,6R is carried out,and the change rule of effective extraction area is obtained.It is concluded that the effective extraction area develops from multiple small cylinders to a large rounded triangular prism with the increase of extraction time,and finally tends to a regular large cylinder.It is expected to provide some reference value for the design of pre-drainage coal seam gas and the prevention and control of actual gas disasters.