祁东煤矿近距离煤层群瓦斯治理顶板拦截定向钻孔试验

Test of roof interception directional drilling for close distance coal seam group gas control in Qidong Coal Mine

  • 摘要: 针对现有近距离煤层群瓦斯治理方法存在工程量大、成本高、周期长的问题,以祁东煤矿94采区为研究对象,提出了采用顶板拦截定向钻孔进行瓦斯治理的方法:首先在开采煤层顶板施工带有多个上向分支孔的顶板拦截定向钻孔,然后利用上向分支孔提前对上邻近煤层瓦斯进行预抽,最后利用主孔在煤层回采过程中对上邻近煤层卸压瓦斯和开采煤层回采工作面及采空区瓦斯进行抽采,从采前预抽和采动卸压抽采2个方面提高了近距离煤层群瓦斯抽采效果,解决了瓦斯赋存参数测量、复杂破碎地层定向成孔与护孔等难题。针对顶板拦截定向钻孔设计与施工难题,采用定向钻孔煤层探查与保压密闭取芯技术、复合定向钻进与复合排渣技术、钢筛管完孔技术,实现了近距离煤层群中顶板拦截定向钻孔高效成孔和长距离精准瓦斯测定。在祁东煤矿94采区进行了现场试验,完成顶板拦截定向钻孔1个,主孔深度608 m,施工分支孔6个,密闭取芯测试瓦斯含量2次,下入护孔筛管485 m,进行瓦斯抽采试验207 d,初始瓦斯抽采纯量为0.35 m3/min,抽采30 d后逐渐下降至0.1 m3/min以下,抽采65 d后整体稳定在0.05 m3/min左右。试验结果表明,顶板拦截定向钻孔可有效预抽邻近煤层瓦斯,提前降低煤层瓦斯含量,从源头上减少后期工作面回采时的采动卸压瓦斯涌出量。

     

    Abstract: In the existing methods of close distance coal seam group gas control, there are problems such as large engineering quantities, high cost and long cycle.In order to solve the above problems, taking the 94 mining area of Qidong Coal Mine as the research object, a gas control method by using roof interception directional drilling is proposed.Firstly, the roof interception directional drilling with multiple upward branch holes is constructed in the roof of the mining coal seam.Secondly, the upward branch holes are used to extract the gas from the upper adjacent coal seam in advance.Finally, the main hole is used to extract the pressure relief gas from the upper adjacent seam and the gas from the working face of the mining coal seam and the goaf during the coal seam mining.This method improves the gas extraction effect of the close coal seam group from two aspects of pre-extraction and mining pressure relief extraction, and solves the problems of gas occurrence parameter measurement and directional drilling and hole protection in complex fractured formation.In order to solve the problems of the design and construction of roof interception directional drilling, the method adopts directional drilling for coal seam exploration and pressure maintaining sealed coring technology, composite directional drilling and composite slag removal technology, and steel screen pipe completion technology to realize efficient hole formation of roof interception directional drilling for close coal seam group and long-distance accurate gas measurement.Field tests are carried out in the 94 mining area of Qidong Coal Mine.One roof interception directional drilling is completed, the main hole depth is 608 m, the construction branch holes are 6, the gas content is tested by sealed coring technology twice, and the lower protective screen pipe is 485 m.The gas extraction test is carried out for 207 days.The initial gas extraction net amount is 0.35 m3/min.After 30 days of extraction, gas extraction net amount gradually drops to below 0.1 m3/min.After 65 days of extraction, the overall gas extraction net amount remains stable.The test results show that the roof interception directional drilling can pre-extract the adjacent coal seam gas effectively, reduce the coal seam gas content in advance, and reduce the pressure relief gas emission from the source during the later mining of the working face.

     

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