碎软煤层顶板梳状长钻孔水力压裂区域瓦斯高效抽采模式

瓦斯区域超前治理是实现煤矿安全、高效及智能化开采的重要保障，针对碎软煤层区域瓦斯高效抽采难题，以陕西韩城矿区3号煤层为研究对象，提出井下煤层顶板梳状长钻孔水力压裂区域瓦斯抽采模式。采用理论分析、数值模拟和现场试验等多手段相结合的方法，验证模式适用性，阐明紧邻煤层顶板梳状钻孔压裂裂缝延展规律、抽采机理和压裂曲线特征，进而建立适用于500 m孔深的集地质条件动态分析、分段水力压裂、封隔器遇阻解卡和压裂范围连续探查于一体的顶板梳状长钻孔裸眼分段水力压裂关键技术体系，实现煤层顶板梳状钻孔主孔轨迹距离煤层5 m左右、多段均匀压裂、压裂范围全孔监测和孔内事故高效处理。以此为基础，在韩城桑树坪二号井开展2孔次的工程实践：压裂主孔深度588 m、距3号煤层2 m左右，单孔压裂6段，压裂范围探查深度381 m、压裂影响半径20 m以上；压裂后，钻孔抽采瓦斯平均体积分数40%以上、瓦斯抽采量1 m3/min以上，抽采效果是常规钻孔的4倍，120 d瓦斯抽采有效半径可达9 m，实现了碎软煤层瓦斯区域高效抽采。并提出了适用于碎软煤层大区域瓦斯抽采以及高瓦斯压力碎软强突煤层远程区域抽采卸压等规模化应用技术思路。

High-efficiency regional gas drainage model after hydraulic fracturing of comb-shaped long boreholes in the roof of broken soft and low permeability coal seam

Advanced management of gas enrichment area is an important guarantee to realize safe, efficient and intelligent mining in coal mine. Aiming at the problem of high-efficiency gas drainage in broken and soft coal seam region, taking No.3 coal seam in Hancheng mining area as the research object, a gas drainage mode of comb-shaped long borehole hydraulic fracturing in the roof of coal seam is proposed. The applicability of the model is verified by means of theoretical analysis, numerical simulation and field test, and the fracture propagation law, gas drainage mechanism, and fracturing curve features of comb-shaped borehole in adjacent roof are clarified. Then, a key technology system of open-hole staged hydraulic fracturing for long comb boreholes in the roof is established, which is suitable for 500 m borehole depth. The system integrates dynamic analysis of geological conditions, staged fracturing, packer blockage release and continuous exploration of fracturing range, realizing the main hole track of comb borehole in coal seam roof about 5 m away from the coal seam, multi-stage uniform fracturing, whole hole monitoring and efficient accident handling. On this basis, the engineering practice of two holes has been carried out in Sangshuping No.2 well. The length of the main fracturing hole is 588 m, about 2.0 m away from No.3 coal seam, and there are 6 fractured sections of single hole. The exploration depth of the fracturing range is 381 m, and the overall fracturing influence radius is more than 20 m. After fracturing, the average gas drainage concentration of borehole is more than 40%, and the gas drainage volume is more than 1 m3/min. The drainage effect is 4 times that of the conventional boreholes, and the effective radius of gas drainage reaches up to 9 m in 120 days, realizing efficient gas drainage in broken soft coal seam area. Furthermore, this study puts forward the technical ideas of large-scale application, which is suitable for large-scale gas drainage in broken soft coal seam and remote regional drainage and pressure relief in broken soft and strong outburst coal seam with high gas pressure.