碎软煤层顶板长钻孔定向压裂瓦斯超前治理工程实践  

Engineering practice of advance gas control for crushed soft coal seams through directional fracturing using a long borehole in the coal seam roof

作　　者：贾秉义 李树刚 陈冬冬 张群 JIA Bingyi;LI Shugang;CHEN Dongdong;ZHANG Qun(CCTEG Xi'an Research Institute(Group)Co.,Ltd.,Xi'an 710077,China;College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China)

机构地区：[1]中煤科工西安研究院(集团)有限公司,陕西西安710077 [2]西安科技大学安全科学与工程学院,陕西西安710054

出　　处：《煤田地质与勘探》2025年第3期34-43,共10页Coal Geology & Exploration

基　　金：国家自然科学基金面上项目(52174207);中煤科工集团西安研究院有限公司科技创新基金项目(2021XAYJSQ07)。

摘　　要：【目的和方法】针对碎软强突煤层瓦斯含量高、压力大,区域预抽钻孔施工过程中喷孔强度大易造成瓦斯超限,钻孔施工效率低等问题,在分析现有区域瓦斯超前抽采卸压技术现状及适应性、近煤层顶板钻孔间接压裂的裂缝扩展延伸特征研究基础上,提出了泥岩层顶板长钻孔套管内定向喷砂射孔分段水力加砂压裂区域瓦斯超前抽采卸压技术,并根据地层特征优化设计了钻孔孔身结构。在安徽淮北芦岭煤矿开展了现场工程试验,完成1个钻孔的钻探施工和套管固孔,孔深520 m,下入一级套管110 m,直径219 mm,二级套管520 m,直径114.3 mm,水泥浆带压固孔。分9段进行射孔压裂,累计射孔39次,形成78个孔眼;单段注液量210~420 m^(3),最大泵注压力17.8~28.3 MPa,加砂比例2.5%~3.3%。【结果与结论】压裂钻孔抽采第257天时,累计抽采瓦斯纯量超过8×10^(5)m^(3),区域预抽率达15.5%。压裂钻孔水平段左右两侧0~15 m和15~30 m范围内瓦斯体积分数降幅分别达27.05%和11.36%;距压裂钻孔平面距离0、15 m处瓦斯压力由2.78 MPa分别降低至1.14 MPa和1.75 MPa,压力降低幅度超过37%。区域瓦斯超前抽采卸压效果明显,技术可行性和有效性得到了验证。超前抽采卸压区域预抽钻孔百孔喷孔率和喷孔强度分别降低了57.89%和67.11%;预抽钻孔一次成孔率提高19%,补孔率降幅达74.87%,钻机施工平均台班效率同比提高了34%。预抽钻孔施工期间,未发生瓦斯异常事件,安全效益显著。该技术可为类似地质条件矿井瓦斯灾害超前治理提供借鉴,已进一步推广至淮南矿区。[Objective and Methods]The crushed soft coal seams susceptible to intense coal and gas outbursts exhibit high gas content and pressure.Consequently,during borehole drilling for regional gas pre-drainage in such coal seams,high blowout intensity is prone to cause gas overrun and low drilling efficiency.To accelerate its development,this study analyzed the status and adaptability of existing technologies for regional advance gas drainage and pressure relief,as well as the fracture propagation characteristics of coal seam roofs during indirect fracturing using boreholes near the roofs.Accordingly,this study proposed an advance gas drainage and pressure relief technology for crushed soft coal seams with mudstone roofs,which integrates directional sandblasting perforation and proppant injection-based segmented hydraulic fracturing within the borehole casing.Furthermore,this study optimized the borehole structure based on stratigraphic characteristics.To verify the proposed technology,this study conducted a field engineering experiment at the Luling coal mine,Huaibei mining area,Anhui Province,completing the drilling and casing cementing of a 520-mdeep borehole.The casing cementing was achieved using a 110-m-long surface casing(diameter:219 mm),a 520-mlong intermediate casing(diameter:114.3 mm),and cement slurry injection under pressure.The borehole was divided into nine segments for perforation and fracturing,with 78 holes formed through 39 perforations.The hydraulic fracturing was implemented with single-segment fluid injection volumes ranging from 210 m^(3)to 420 m^(3),maximum pumping pressures from 17.8 MPa to 28.3 MPa,and injected proppant ratios from 2.5%to 3.3%.[Results and Conclusions]After 257 days of gas drainage from the borehole subjected to fracturing,the cumulative pure gas production exceeded 8×10^(5)m^(3),with a regional pre-drainage rate reaching up to 15.5%.The gas volume fractions within ranges of 0‒15 m and 15‒30 m on both sides of the borehole’s horizontal section decreased by 27.05%and 11.3

关 键 词：碎软煤层 超前抽采卸压 定向压裂 顶板长钻孔 泥岩 瓦斯抽采 

分 类 号：TD713[矿业工程—矿井通风与安全]