张俭，刘乐，赵继展，等. 煤层顶板定向长钻孔水力加砂分段压裂技术与装备[J]. 煤田地质与勘探，2022，50(8)：37−44. DOI: 10.12363/issn.1001-1986.22.03.0201
引用本文: 张俭，刘乐，赵继展，等. 煤层顶板定向长钻孔水力加砂分段压裂技术与装备[J]. 煤田地质与勘探，2022，50(8)：37−44. DOI: 10.12363/issn.1001-1986.22.03.0201
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ZHANG Jian，LIU Le，ZHAO Jizhan，et al. Research on hydraulic fracturing technology and equipment of directional long drilling with sand in coal seam roof[J]. Coal Geology & Exploration，2022，50(8)：37−44. DOI: 10.12363/issn.1001-1986.22.03.0201
Citation: ZHANG Jian，LIU Le，ZHAO Jizhan，et al. Research on hydraulic fracturing technology and equipment of directional long drilling with sand in coal seam roof[J]. Coal Geology & Exploration，2022，50(8)：37−44. DOI: 10.12363/issn.1001-1986.22.03.0201
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煤层顶板定向长钻孔水力加砂分段压裂技术与装备

Research on hydraulic fracturing technology and equipment of directional long drilling with sand in coal seam roof

    摘要
  • 摘要: 针对碎软煤层渗透率低、瓦斯抽采衰减快、压裂不均匀、裂缝易闭合、瓦斯抽采效果差、无法实现区域瓦斯超前预抽的问题，提出了煤层顶板定向长钻孔水力加砂分段压裂强化瓦斯抽采的技术思路，研发适合煤矿井下煤层顶板定向长钻孔水力加砂分段压裂煤层增透技术，研制了成套的煤矿井下水力加砂压裂泵组装备、定向喷砂射孔装置及工具组合、防砂封隔器及工具组合。水力压裂泵组装备最大排量90 m3/h，最大泵注压力70 MPa，最大携砂能力20%，支撑剂粒径小于等于1 mm；定向喷砂射孔装置通过水压驱动喷射器定向，最大旋转角度180°；防砂封隔器最大承压70 MPa，最大膨胀系数为2。研发的定向长钻孔连续定向喷砂射孔工艺技术和定向长钻孔拖动式水力加砂分段压裂工艺技术，在山西阳泉新景煤矿井下开展工程试验，完成2个压裂钻孔(孔深均为609 m)共计16段水力加砂分段压裂施工，累计实施80次定向喷砂射孔作业，石英砂的体积分数2%~3%，定向喷砂射孔压力22.6~28.6 MPa，共计使用石英砂19.8 t；水力加砂分段压裂单段注入压裂液153.8~235.1 m3、核桃壳砂的体积分数2.02%~2.56%，累计注入压裂液2 808.57 m3，注入核桃壳砂36.47 t；综合评价本次水力加砂分段压裂影响半径为20~38 m，统计分析压裂后2个钻场100 d瓦斯抽采数据，1号钻场、2号钻场日均瓦斯抽采纯量分别为1 025、2 811m3。试验结果表明：压裂装备加砂量大，施工排量大，能够实现连续作业，压裂后煤层透气性显著增加，极大地提高瓦斯抽采浓度和瓦斯抽采纯量。研究成果对碎软煤层区域瓦斯增透提供新思路，为我国类似矿区区域瓦斯超前治理提供技术借鉴。

     

    Abstract: Due to low permeability, fast gas-rate decline, uneven fracturing, easy fracture closure, it is difficult to perform advance gas extraction in broken-soft coal seams. Aimed at these issues, this study has been proposed a new idea to enhance the coalbed permeability and eventually the gas extraction, which is based on roof-supporting, long-reach directional drilling, and hydraulic fracturing. Corresponding equipment including fracturing pump unit, directional sandblasting perforation assembly, sand control packer and tools have been developed. Specifically, the pumping unit is capable of a pumping rate up to 90 m3/h, a pumping pressure up to 70 MPa, and a proppant concentration up to 20%, and a proppant particle size up to 1 mm; The directional sandblasting perforation assembly is driven by hydraulic pressure, with a maximum rotation angle of 180°; And the sand control packer can uphold up to 70 MPa with a maximum expansion factor of 2. In addition, we applied such technologies as long-reach directional drilling, continuous sandblasting perforation, and multistage hydraulic fracturing to a field pilot test in Xinjing coal mine, Yangquan, Shanxi Province. A total of 80 directional sandblasting shots at a pressure of 22.6-28.6 MPa, and 16 fracturing stages were carried out in two boreholes at an average depth of 609 m. And 19.8 t silica sand (a concentration of 2-3 vol.%), 2808.5 m3 fracturing fluid (153.8-235.1 m3 for a single fracturing stage), and 36.47 t walnut shell (a concentration of 2.02%-2.56%) were injected. The tests achieved a fracture half-length of 20-38 m in estimation, and average gas rates of 1025 and 2811 m3/d in 100 days after the treatment. Besides, it is found that the fracturing equipment has a large sand injection capacity, high pumping rate, and continuous operation. The coal seam permeability was significantly enhanced after fracturing, which led to great improvement in gas concentration and purity. This research provide new ideas for permeability enhancement in broken-soft coal seams and serves as a good reference for advance treatment in similar mining areas in China.

     

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