考虑滤失效应的煤层水力压裂与裂隙扩展关系研究  

Relationship between hydraulic fracturing and fracture propagation in coal seams considering filtration effect

作　　者：王刚[1,2] 王恩茂 隆清明 徐浩[1,2] 陈雪畅 刘昆轮 WANG Gang;WANG En-mao;LONG Qing-ming;XU Hao;CHEN Xue-chang;LIU Kun-lun(College of Safety and Environmental Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China;State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology,Shandong University of Science and Technology,Qingdao,Shandong 266590,China;CCTEG Chongqing Research Institute,Chongqing 400000,China;National Energy Group Xinjiang Energy Co.,Ltd.,Urumqi,Xinjiang 830000,China)

机构地区：[1]山东科技大学安全与环境工程学院,山东青岛266590 [2]山东科技大学矿山灾害预防控制省部共建国家重点实验室培育基地,山东青岛266590 [3]中煤科工集团重庆研究院有限公司,重庆400000 [4]国家能源集团新疆能源有限责任公司,新疆乌鲁木齐830000

出　　处：《岩土力学》2025年第4期1071-1083,共13页Rock and Soil Mechanics

基　　金：国家自然科学基金面上项目(No.52174194);国家自然科学基金青年项目(No.52404227)。

摘　　要：煤体是多孔介质结构,水力压裂过程中液体会沿原生孔裂隙流失,即滤失效应,降低水力压裂施工效果。同时,煤层水力压裂压力变化与裂隙扩展之间的对应关系没有形成体系,无法准确判断水力压裂对煤体的损伤情况。为此,以乌东煤矿为研究背景,采用理论分析、实验室试验以及现场试验的技术手段,首先,以岩石力学圆孔问题围岩应力分析理论和煤体渗流理论为基础,结合孔壁应力集中诱发拉伸破裂准则理论,分析考虑滤失条件下的水力压裂起裂机制;其次,开展急倾斜顶煤水力压裂试验,依据试验煤样裂隙扩展情况,判断急倾斜顶煤压力曲线与煤岩体的破断关系;再次,开展现场水力压裂试验,进一步判断现场压力曲线与顶煤破断之间的关系;最后,总结分析出4种压力曲线演化规律,作为判断煤岩体水力压裂效果的依据。研究结果表明:当钻孔内部注水压力达到煤岩抗拉强度相等的拉应力时,孔壁出现首次开裂。水力压裂过程中,注水流量必须大于滤失量,且注水速率越大,憋压过程所用时间越短。压力曲线可划分为4种类型:(1)一次起裂型,(2)裂隙导通型,(3)流体滤失型,(4)二次起裂型。在压裂过程中流体滤失型占比越小压裂效果越优。该研究结果能够为现场水力压裂对煤体损伤效果提供判断依据。Coal is a porous medium structure.During the hydraulic fracturing process,fluids may escape along pre-existing pores and fractures,known as filtration effect,which reduces the effectiveness of hydraulic fracturing operations.Additionally,there is no established system for the relationship between pressure changes during coal seam hydraulic fracturing and fracture propagation,making it impossible to accurately assess the damage caused by hydraulic fracturing to coal.To address this issue,the Wudong Coal Mine is chosen as the research background,and theoretical analysis,laboratory experiments,and on-site tests are conducted.Firstly,the initiation mechanism of hydraulic fracturing under loss conditions is analyzed based on the stress analysis theory of surrounding rock in rock mechanics circular hole problems,coal seepage theory,and the theory of tensile fracture criterion induced by stress concentration on hole walls.Secondly,an experiment of hydraulic fracturing for steeply inclined top coal is conducted to determine the relationship between the pressure curve of steeply inclined top coal and the fracture of coal rock mass according to the crack propagation situation of the experimental coal sample.Thirdly,an on-site hydraulic fracturing test is carried out to further determine the relationship between the on-site pressure curve and the fracture of top coal.Finally,four types of pressure curve evolution patterns are summarized as a basis for judging the effectiveness of hydraulic fracturing in coal rock mass.The research results show that when the internal water injection pressure in the borehole reaches the tensile strength equal to that of the coal rock,the first crack appears at the borehole wall.During the hydraulic fracturing process,the water injection flow rate must be greater than the leakage rate,and the higher the water injection rate,the shorter the pressurization process duration.The pressure curves can be categorized into four types:(1)single initiation type,(2)fracture connection type,(3)fluid loss t

关 键 词：水力压裂 急倾斜煤层 注水压力 原生孔裂隙 滤失效应 

分 类 号：TU452[建筑科学—岩土工程]