顶板定向长钻孔“以孔代巷”抽采瓦斯技术研究

Gas Drainage Technology by Directional Long Borehole in Roof to Replace Gateway

为探究行之有效的“以孔代巷”瓦斯抽采技术,解决端氏煤矿高抽巷工程量大、经济成本高等问题,提出顶板定向长钻孔替代高抽巷治理采空区瓦斯模式。采用FLAC 3D数值模拟确定3号煤层顶板以上15~45 m为最佳抽采层位,并基于定向钻进轨迹控制技术,在端氏煤矿3019工作面进行成孔试验。结果表明:钻进轨迹能够按照预设参数实施,成孔直径达153 mm,一次成孔深度420 m以上,钻孔进入稳定抽采阶段的平均抽采瓦斯浓度达18%、平均抽采瓦斯纯流量达8.7 m^3/min,钻孔抽采条件下工作面瓦斯抽采率达36.7%,工作面上隅角瓦斯浓度控制在0.50%以下,解决了瓦斯超限问题。与高抽巷抽采技术相比,顶板定向长钻孔成本降低62.5%、施工工期缩短50%,验证了“以孔代巷”的合理性和可行性。

In order to explore the effective method of gas drainage by borehole to replace gateway,to solve the problem of large work quantity and high economic cost in high drainage roadway in Duanshi Coal Mine,it is pointed out that the roof directional long borehole can replace the high drainage roadway to control gas in goaf.FLAC 3D numerical simulation was used to determine that from 15 m to 45 m above the roof of No.3 coal seam was the best extraction stratum.Based on the directional drilling trajectory control technology,the hole formation test was carried out in 3019 working face of Duanshi Coal Mine.The results show that the drilling trajectory can be implemented according to the preset parameters,with the hole forming diameter up to 153 mm and the hole forming depth over 420 m.When the hole get into stable extraction stage,the average volume fraction of gas extraction is 18%,the average gas extraction purity is 8.7 m^3/min,the gas drainage rate in working face reaches 36.7%under the condition of borehole extraction,and the gas volume fraction of upper corner in working face is under 0.50%,the problem of gas over limit is solved.Compared with the technology of high drainage roadway,the cost of directional long borehole in roof is reduced by 62.5%and the construction period is shortened by 50%,which verifies the rationality and feasibility of gas drainage by borehole to replace gateway.