地面直井水压致裂防控巨厚硬岩运动型矿震试验研究

Experimental study on the prevention and control of mine earthquake by high pressure water fracturing of huge thick strata in vertical shaft

巨厚坚硬岩层运动产生的矿震和冲击地压灾害防控难度大,已经成为我国多个巨厚坚硬岩层矿区矿井安全生产的主要障碍。以东滩煤矿六采区巨厚硬岩工作面开采为工程背景,根据工作面开采期间矿震发生规律、地层结构特征及煤层开采条件,提出了地面直井分段水压致裂防控深井巨厚硬岩运动型矿震的方法,通过地面直井压裂降低巨厚硬岩的完整性、减小巨厚硬岩运动释放的弹性能,压裂期间采用自主研发的高精度连续采集微震监测系统对压裂过程中形成的裂缝形态进行监测,通过对压裂过程中的管路压力曲线、微震事件以及压裂后63_(上)06工作面回采过程中发生的微震事件规律进行分析,得到以下结论:(1)通过对压裂曲线以及压裂过程中接收到的有效微震事件在时间上分布规律的分析,将地面直井巨厚岩层水压致裂裂缝形成发育的整个过程分为起裂、岩石裂隙扩展、主裂缝形成、主裂缝延伸与次生裂缝形成和裂缝闭合返排5个阶段;(2)根据微震监测结果,地面直井高压水致裂形成的主裂缝方向143°~150°,长度为220~300 m,竖直高度300~344 m,基本实现了对目标巨厚硬岩的全厚压裂;(3)根据63_(上)06工作面在地面直井压裂区域开采期间的微震监测结果,对比相邻3个工作面在0~500 m开采期间1.5级以上矿震事件平均减少约54%,基本实现了预期的地面压裂减震目标,为东滩煤矿六采区巨厚硬岩工作面安全开采提供了保障。

It is difficult to prevent and control mine earthquakes and rock burst disasters caused by the movement of huge and hard rock formations,which has become a major obstacle to safe production in mines with many huge and hard rock formations in China.Taking the work face with huge thick hard rock strata in the sixth mining area of Dongtan Coal Mine as an engineering background,according to the law of occurrence of earthquakes during mining,the characteristics of the strata structure and the mining conditions of the coal seam,the ground vertical shaft segmented hydraulic fracturing has been proposed to prevent thick and hard rock motion-type mine seismic.Through the ground vertical well fracturing,the integrity of the thick hard rock is reduced,and the elastic energy released by the movement of the thick hard rock is reduced.The self-developed high-precision continuous acquisition micro-seismic monitoring system during the fracturing period is used to monitor the fracture morphology formed during the fracturing process.The pipeline pressure curve during the fracturing process,the micro-seismic events,and the law of micro-seismic events occurred during the recovery process at the 63 up 06 face after fracturing are analyzed.The following conclusions are obtained:(1)Based on the analysis of the fracturing curve and the temporal distribution of the effective micro-seismic events received during the fracturing process,the entire process of the formation and development of hydraulic fracturing fractures in the huge thick rock formations in vertical ground wells is divided into five stages including initiation,rock fracture expansion,main crack formation,main crack extension and crack closure backflow.(2)According to the micro-seismic monitoring results,the direction of the main fractures formed by high-pressure water fracturing in vertical ground wells is between 143°and 150°,the length is between 220 m and 300 m,and the vertical height is between 300 m and 344 m.Full thickness fracturing of thick hard rock is achieved.(3)According to the micro-seismic monitoring results of the 63 up 06 working face during the mining operation in the ground vertical well fracturing area,compared with the three adjacent working faces during the 0-500 m mining period,the average reduction of 1.5 magnitude or more mine earthquake events is about 54%,and the expected ground surface is basically realized.The fracturing damping target provides a guarantee for the safe mining of the huge thick hard rock face in the sixth mining area of Dongtan Coal Mine.