厚煤层采空区定向孔分域抽采研究及应用

Research and application of directional drilling sub area extraction in thick coal seam goaf

为提高厚煤层采空区定向钻孔的瓦斯抽采效率,针对山西某高瓦斯矿井采煤工作面,采用理论分析和FLUENT数值模拟相结合的方法研究采动裂隙分域演化特性,提出覆岩裂隙场分域准则,确定定向钻孔布置区域与核心抽采布置范围,并在采空区现场开展定向钻孔分域抽采瓦斯试验。结果表明:破断裂隙密集区内,岩层断裂穿层裂隙发育较明显、瓦斯聚集显著,且钻孔稳定性高,是布置定向钻孔的最佳区域;并将与回风巷中心线水平距离3~13 m,与煤层顶板垂直距离10~18 m的区域设定为核心抽采区域。定向钻孔分域抽采试验中,单孔抽采瓦斯体积分数平均提升22.355%,单孔瓦斯抽采纯量平均提升1.295 m 3/min,该结论验证了厚煤层采空区定向钻孔分域抽采方法的实用性与合理性。

In order to improve the gas drainage efficiency of directional drilling in thick coal seam goaf,the experiment was carried out in a coal face of a high gas mine in Shanxi province.The method of combining theoretical analysis with FLUENT numerical simulation was used to study the regional evolution characteristics of mining induced fractures.According to the experimental results,the zoning criteria of overburden fracture field were proposed to determine the layout area of directional boreholes and the layout range of key gas drainage boreholes.The gas extraction test of goaf by directional long boreholes was carried out on the site of goaf.The test results show that in the fracture concentrated area,the longitudinal development of fractures is obvious,the gas accumulation is significant,and the stability of gas drainage boreholes is high.Therefore,this area is the best area for directional drilling.The key area for the arrangement of gas drainage boreholes is the area with a horizontal distance of 3-13 m from the center line of the air return roadway and a vertical distance of 10-18 m from the roof of the coal seam.In the experiment of gas extraction in layers by directional boreholes,the average volume fraction of single hole gas extraction increases by 22.355%,and the average pure gas extraction volume of single hole increases by 1.295 m 3/min.This conclusion verifies the practicability and rationality of the gas drainage method of directional drilling in goaf of thick coal seam.