基于井下煤层水力压裂的微震时空发育规律研究

Study on Time-Space Development Law of Microseism Based on Hydraulic Fracturing of Underground Coal Seam

为了研究井下煤层水力压裂过程中的微震活动规律,以龙凤煤矿首采区1905工作面开展的UDFD瓦斯治理项目为工程背景,采用KJ1073微震监测系统对压裂过程进行实时、动态的监测。监测研究表明:(1)微震事件的发育具有时间效应,发育范围随压裂时间的增加逐渐扩大,微震事件能量具有周期性,分析与煤岩体裂隙扩展相关:煤岩体弹性压缩→加速扩展→减速扩展→煤岩体弹性压缩的一个循环过程;(2)微震事件发育方向与压裂液体流动的方向、煤体的倾角方向基本一致,发育范围最长为184 m,最短为100 m,垂向集中在9#煤层顶、底板10 m以内;(3)对微震数据进行分类,并采用置信椭圆分析,表明LF7-1、LF7-2压裂孔之间裂隙发育,发生联通,得到了有效的压裂,在后期的瓦斯抽采中得到验证。上述研究探明了压裂裂缝延伸扩展方向和影响范围,对进一步指导现场施工,优化压裂钻孔布置提供依据。

In order to study the law of microseismic activity in the hydraulic fracturing process of underground coal seam,the KJ1073 microseismic monitoring system is used to monitor the fracturing process in real time and dynamically based on the UDFD gas treatment project carried out in the 1905 working face of the first mining area of Longfeng coal mine.Microseismic monitoring research shows that:(1)The development of microseismic events has a time effect,and the development range gradually expands with the increase of fracturing time.The energy of microseismic events is periodic,and the analysis is related to the expansion of coal and rock cracks:a cyclic process of elastic compression→accelerated expansion→decelerated expansion→elastic compression of coal and rock.(2)The development direction of microseismic events is basically consistent with the direction of fracturing liquid flow and the inclination direction of coal mass,with the longest development range being 184 m and the shortest being 100 m,and the vertical direction is concentrated within 10 m of the top and bottom of No.9 coal seam.(3)The microseismic data were classified,and confidence ellipse analysis was used to show that the fractures between LF7-1 and LF7-2 pressure fractures developed and connected,and effective fracturing was obtained,and the gas extraction effect in the later stage was verified.The above research proved the direction of fracture extension and influence range,and provided a basis for further guidance of site construction,optimization of fracturing borehole layout,gas control and mine safety mining.