特厚煤层坚硬顶板水力压裂控制技术研究

Control technology of hard roof hydraulic fracturing in extra-thick coal seam

为了解决了矿井特厚煤层坚硬顶板岩层高应力集中及冲击地压的难题,采用特厚坚硬顶板水力压裂施工工艺,在彬长矿区孟村煤矿401101工作面采用水力压裂技术进行压裂现场试验,通过理论和现场监测等多种手段对压裂孔应力场进行了综合分析。结果表明:钻孔孔壁在压裂位置处都有不同程度的破坏,产生斜切、纵向和横向三种裂隙,压裂后孔间岩层裂隙在最小水平应力方向上能较好地贯穿,在垂向上老顶压裂效果可观;工作面进入水力预裂区域后高级别能量微震事件频次占比显著降低,微震事件逐渐由工作面后方转移向工作面前方;工作面推进至高压水预裂区范围后,端头范围内顶板垮落充分,支架工作阻力峰值和增载系数普遍较未压裂区增大,支架的空载和漏失率降低。表明顶板水力压裂技术工艺可以有效为特厚煤层坚硬顶板卸压控制提供有力技术支持。

Aiming at the high stress concentration and rock burst hazard in the hard roof rock of extra-thick coal seam, the hydraulic fracturing construction technology for hard roof of extra-thick coal seam is tested at the 401101 working face of Mengcun Coal Mine in Binchang mining area, and the fracture hole stress field is comprehensively analyzed through theoretical analysis and various on-site monitoring methods. The results show that the borehole wall is damaged to different degrees at the fracturing position, resulting in three types of cracks: oblique cut, longitudinal and transverse fractures. After fracturing, the rock formations between the holes can penetrate well in the direction of the minimum horizontal stress. The vertical fracturing effect of the old roof is considerable;after the working face enters the hydraulic pre-fracturing area, the frequency of high-level energy microseismic events is significantly reduced;after the working face advances to the high-pressure hydraulic pre-fracturing area, the roof collapses sufficiently in the end range, and the peak working resistance and load increase coefficient of the supports are generally larger than those in the non-fracturing zone, and the empty load and leakage rate of the supports are reduced. It shows that the roof hydraulic fracturing technology can provide strong technical support for the control of hard roof pressure relief in extra-thick coal seams.