基于煤体各向异性的煤层瓦斯有效抽采区域研究

Study on effective gas drainage area based on anisotropic coal seam

为了探究影响射流割缝钻孔周围有效抽采区域变化的因素,基于煤体的各向异性考虑了瓦斯抽采过程煤体应变场和瓦斯渗流场的耦合作用,探讨了不同垂直地应力、初始瓦斯压力以及初始渗透率等参数对射流割缝钻孔有效抽采区域的影响规律。结果表明:垂直地应力越大,煤体的渗透率越低,有效抽采区域逐渐减小;初始瓦斯压力越大,抽采相同时间后瓦斯压力越难降至0.74MPa以下,有效抽采区域逐渐减小;初始渗透率越大,煤体裂隙瓦斯流动速度越快,导致在相同抽采负压下有效抽采区域逐渐增大。各向异性煤体的模拟结果与现场测试结果基本相符,证明了各向异性煤层垂直层理方向有效抽采半径是现场布孔的合理指标。

The paper is devoted to explore parameters that affect the effective drainage area around the hydraulic slotting.The coupling effect of the coal strain field and the gas seepage field in gas drainage is studied based on the anisotropy of coal.The influences of different vertical geostress,initial gas pressure,and initial permeability on the effective drainage area of hydraulic slotting are also analyzed.The results show that higher vertical ground stress is associated with lower coal permeability,which leads to the gradual reduction of effective drainage area.The larger the initial gas pressure is,the more difficulty it is to reduce the gas pressure around the borehole to 0.74 MPa or less,with the effective drainage area being gradually reduced.The larger the initial permeability,the higher the gas flow velocity of the coal body fissure,and the effective drainage area gradually increases under the same drainage negative pressure.The simulation results of anisotropic coal body are basically consistent with the field test results,which proves that the effective drainage radius of the anisotropic coal seam vertical bedding direction is a reasonable index of the field hole.