石门揭煤区液态CO_2致裂增透加速消突技术
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摘要
针对低透气强突出煤层在石门揭煤过程中消突工程量大、作业环节复杂及揭煤周期长等特点,在揭煤前布置的瓦斯抽采孔内实施液态CO_2相变致裂增透卸压技术,经理论计算和现场考察确定4号煤层的增透半径为6 m。该技术在-650运输巷揭穿4号煤层的工作面进行了试验,结果表明:致裂前后,钻孔平均抽采瓦斯浓度从20.2%提升至42.6%,单孔平均日抽采量从1.56 m3/d提升至3.76 m3/d,且近20 d内保持高效抽采,在1个月内完成抽采达标和消突任务,抽采率为48.16%,缩短抽采时间43%;在揭煤区取样测试煤体的残余瓦斯含量平均值为5.41m3/t,反演残余瓦斯压力平均值0.27 MPa,采用钻屑解吸指标法测试钻屑量S最大值4.7 kg/m,钻屑解吸指标△h2最大为140 Pa,所有测值均小于突出临界值;煤层揭穿期间回风流瓦斯浓度仅有4%,实现安全高效快速揭煤。
Aiming at the characteristics of the larger outburst elimination amount, complex working link and the long cycle of uncovering coal in the process of crosscut coal uncovering in low permeability outburst seam, the technology of liquid CO_2 phase transition fracturing was used in gas drainage hole. The permeability increase radius of No.4 coal seam is 6 m by theoretical calculation and field investigation. The technology was tested in the face of-650 transport lane which would uncover the No.4 coal seam. The results showed that the average drainage concentration from a single gas borehole increased from 20.2% to 42.6%.The average single hole drainage quantity increased from 1.56 m3/d to 3.76 m3/d before and after fracturing. Gas drainage maintained efficient in the past 20 days. Drainage standards were completed in a month. The extraction rate was 48.16% and the extraction time was shortened by 43%. The average residual gas content was 5.41 m3/t, and the average residual gas pressure was0.27 MPa. The maximum drilling cuttings volume S was 4.7 kg/m and desorption index of drill cuttings △h2 was 140 Pa. All test values were less than the critical value. The return air gas concentration is only 4% after the uncovering coal seam, which achieved safe, efficient and rapid cross-cut coal uncovering.
Aiming at the characteristics of the larger outburst elimination amount, complex working link and the long cycle of uncovering coal in the process of crosscut coal uncovering in low permeability outburst seam, the technology of liquid CO_2 phase transition fracturing was used in gas drainage hole. The permeability increase radius of No.4 coal seam is 6 m by theoretical calculation and field investigation. The technology was tested in the face of-650 transport lane which would uncover the No.4 coal seam. The results showed that the average drainage concentration from a single gas borehole increased from 20.2% to 42.6%.The average single hole drainage quantity increased from 1.56 m3/d to 3.76 m3/d before and after fracturing. Gas drainage maintained efficient in the past 20 days. Drainage standards were completed in a month. The extraction rate was 48.16% and the extraction time was shortened by 43%. The average residual gas content was 5.41 m3/t, and the average residual gas pressure was0.27 MPa. The maximum drilling cuttings volume S was 4.7 kg/m and desorption index of drill cuttings △h2 was 140 Pa. All test values were less than the critical value. The return air gas concentration is only 4% after the uncovering coal seam, which achieved safe, efficient and rapid cross-cut coal uncovering.
引文
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[4]孙大发,陈久福,龙建明,等.高压水力压裂技术在石门揭煤中的试验研究[J].煤炭科学技术,2013,41(S):163-165.
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[7]陈鹏,郭金栋,李忠辉,等.高瓦斯低透气性煤层石门揭煤卸压爆破试验[J].煤炭科学技术,2009,37(6):49-52.
[8]刘健,刘泽功,蔡峰.石门揭煤深孔预裂爆破增透效果试验研究[J].煤炭科学技术,2011,39(6):30-32.
[9]孙文忠.低渗煤层CO2预裂增透高效瓦斯抽采原理及应用[J].煤炭科学技术,2017,45(1):100-105.
[10]李守巨,费鸿禄,何庆志,等.讨论爆照气体的爆炸作用[J].阜新矿业学院学报(自然科学版),1992(3):46-49.