大直径地面钻井采空区采动区瓦斯抽采理论与技术

地面钻井抽采采空采动区瓦斯技术在世界范围内的应用越来越广泛,然而仍存在着瓦斯流量和浓度偏低以及钻井稳定性差的问题。基于淮南矿业集团和澳大利亚的应用实践,开展了大直径地面钻井提高瓦斯抽采效果的理论与技术研究。通过对围岩采动影响和瓦斯抽采效果的数值模拟,参考瓦斯高效抽采范围的高位环形体理念,进行了抽采管径分别为244.5 mm和177.8 mm的大直径地面钻井设计和抽采瓦斯试验。试验结果表明:大直径地面钻井在抽采效果、控制工作面瓦斯涌出以及钻井稳定性上均明显优于普通钻井,瓦斯抽采总量可达316.7万m3,瓦斯纯量达170万m3,服务时间达106 d,能够有效地控制工作面回风瓦斯浓度;地面钻井布置于回风巷一侧在抽采效果上优于进风巷一侧,前者瓦斯抽采量和浓度分别高于后者33.7%和75.3%。

Theory and technology of goaf gas drainage with large-diameter surface boreholes

Coal mine goaf drainage with surface boreholes is increasingly used in coal mines worldwide.However，poor performance of some of these surface gas boreholes is often experienced in terms of the gas concentration，flowrate and borehole stability.In order to improve performance，theoretical studies and field investigations were carried out to develop optimal surface borehole designs based on the experience from Huainan and Australia in recent years.Through the extensive numerical modelling of mining impact in the surrounding strata，and performance of various gas drainage configurations，and by applying the concept of the 3D annular-shaped overlying zone for optimal methane drainage，the trials using large diameter boreholes with diameters of 244.5 mm and 177.8 mm were designed and implemented.The trial results demonstrate that the large diameter boreholes perform significantly better than conventional boreholes in terms of total gas captured，longwall gas control effectiveness，and borehole stability.The total gas captured from a single large borehole can reach 3.167 million m3 with 1.7 million m3 of pure methane，and the borehole productive life is 106 days.The methane concentration in the longwall return gateroad is effectively controlled during the operation of the large boreholes.The trial results also show that the surface borehole located on the longwall return side performes better than that on the intake side.The total gas captured from the return side borehole is 33.7% more than that from the intake side and the methane concentration is 75.3% higher.