基于扩散-渗流机理瓦斯抽采三维模拟研究

Research on 3D Numerical Simulation of Gas Extraction Base on Diffusion-seepage Mechanism

根据煤体孔裂隙多重介质特性,分析煤体内瓦斯在基质孔隙和裂隙中不同的运移机理,建立瓦斯流动方程;考虑孔隙压力、吸附膨胀效应对渗透率的综合影响,建立渗透率动态方程;以弹性力学为基础,建立煤体变形控制方程;共同构建能够描述瓦斯扩散-渗流运移机理的耦合模型。以真实煤层赋存参数为例,根据理论模型对COMSOL Multiphysics进行二次开发,建立三维瓦斯抽采模型,模拟研究不同抽采时间下的瓦斯压力、抽采有效半径变化规律;利用压降法进行现场实测考察,现场实测结果与模拟结果基本吻合,验证了扩散-渗流耦合模型及三维数值模拟的可靠性,从而为该矿实际瓦斯抽采工作提供安全可靠的理论技术指导。

According to the characteristics of fore-fracture structure multiple medium of coal mass,and analysis on the gas different migration mechanism in the matrix pores and fractures to build the gas flow equation,and by considering the comprehensive influence of the pore pressure and adsorption-expansion on the permeability,the dynamic equations of permeability are got. On the basis of elastic mechanics,the control equation of coal deformation is establised. Three equations have been used to construct the coupling model,which can describe the gas diffusionseepage migration mechanism. Based on the actual coal seam occurrence parameters,the couple model is introduced to the COMSOL Multiphysics for secondary development to build 3 D model of gas extraction,which can be used to research the variation law of gas pressure and extraction effective radius with different extraction time. Eventually,experimental investigation with the method of pressure drop was conducted to verify the numerical simulation. The investigation results approximately agree with those by the numerical simulation,so it can verify the reliability of the diffusion-seepage coupling model and 3 D numerical simulation. The results can provide the safe and reliable technical guidance to actual work of gas extraction in this coal mine.