【摘要】 为揭示渗透率各向异性对钻孔瓦斯抽采的影响,假设煤层是一种孔隙-裂隙结构的弹性连续介质,构建各向异性渗透率方程;基于多物理场耦合理论,建立考虑气-水两相流的煤层流固耦合模型,结合试验测得的煤层不同方向上的渗透率,模拟确定煤层瓦斯抽采的合理钻孔间距和钻孔布置方向。结果表明:由于渗透率各向异性,在钻孔附近形成椭圆形的压降区域,该区域向煤层边界扩展,逐渐变为鼓形;在模拟工况下,抽采120天内达标的合理钻孔间距应为2.346~2.598 m;钻孔与最大渗透率方向的夹角越大,瓦斯抽采量越大,钻孔布置方向与煤层最大渗透率方向应保持较大夹角。更多还原

【Abstract】 In order to reveal the influence of permeability anisotropy on coal seam gas extraction,an anisotropic permeability equation was derived after assuming that the coal seam is an elastic continuous medium with pore-fracture structure and a hydraulic-mechanical coupling model considering two-phase flow was built for gas extraction,on the basis of the multiple-field coupling theory.Based on the permeability in different directions of coal seam measured by experiment,both the reasonable drilling spacing and the arrangement direction of coal seam gas extraction were determined by numerical simulations.The results show that a pressure reduction zone with elliptical shape is formed near the borehole due to the permeability anisotropy,and then the pressure reduction zone becomes drum shape with the limitation of coal seam thickness,that when taking 120 days as the deadline for gas extraction,the rational space is2.346-2.598 m under the condition of simulated working face,that the gas extraction volume increases with the rising of the angle between borehole direction and maximum permeability direction,and that for the sake of increasing the gas extraction,the direction of drilling arrangement should keep a larger angle with the maximum permeability direction of coal seam.更多还原