低透气性煤层的渗透率试验与瓦斯抽采技术

Permeability test and gas drainage technology of low permeability coal seam

为揭示渗透率及孔隙率结构对低透气性煤层瓦斯抽采的影响,采用理论分析和试验研究方法,针对集贤煤矿9#煤层西二采区四片工作面瓦斯异常涌出与浓度超限的问题,在对工作面瓦斯的来源和向斜构造对瓦斯赋存的影响分析的基础上,实验室采用自压式三轴渗流测试装置测定了不同方向煤样试件的渗透率,应用低场核磁共振测试系统对孔隙结构分布规律进行研究,采用径向流量法对透气性系数进行测定。研究结果表明:煤层渗透率随瓦斯压力增大而降低,且表现出各向异性特征;煤层孔隙发育程度低,则渗透率降低,瓦斯渗透能力较差,吸附瓦斯含量较大,揭示了渗透率对低透气性煤层瓦斯抽采和抽采率影响较大。研究结论对低透气性煤层卸压增透措施和瓦斯抽采钻孔参数的选择具有理论指导意义。

In order to reveal the influence of permeability and porosity structure on gas extraction in low permeability coal seam,theoretical analysis and experimental research methods were adopted to address the abnormal gas emission and excessive concentration of gas from the no.4 working faces in west no.2 mining area of no.9 coal seam in Jixian coal mine.On the basis of the analysis of gas source and the influence of syncline structure on gas occurrence in the working face,the permeability of coal samples in different directions was measured by a self-pressurized triaxial seepage testing device,the low field nuclear magnetic resonance test system was used to test the distribution law of the pore structure of the coal seam,and the permeability of the coal seam was measured by the radial flow method.The results show that the permeability of coal seam has significant influence on gas extraction and extraction rate,and the permeability decreases with the increase of gas pressure and shows anisotropy.The worse the porosity development of coal seam,the lower the permeability of coal seam,and the worse the gas permeability,the higher the adsorption gas content.It is revealed that permeability has a great influence on gas extraction and extraction rate in low permeability coal seam.The research conclusion has theoretical guiding significance to the selection of pressure relief and permeability improvement measures of low permeability coal seam and the parameters of gas extraction borehole.