煤岩层水力致裂的应力扰动效应研究.pdf

国家优秀青年科学基金项目（51522406）资助 硕士学位论文 煤岩层水力致裂的应力扰动效应研究 Stress Disturbance Effect Induced by Hydraulic Fracturing in Coal and Rock Seams 作 者杨 帆 导 师黄炳香 教授 中国矿业大学 二○一七年五月 中图分类号 TD8 学校代码 10290 UDC 622 密 级 公开 国家优秀青年科学基金项目（51522406）资助 中国矿业大学 硕士学位论文 煤岩层水力致裂的应力扰动效应研究 Stress Disturbance Effect Induced by Hydraulic Fracturing in Coal and Rock Seams 作 者 杨 帆 导 师 黄炳香 申请学位 工学硕士 培养单位 矿业工程学院 学科专业 采矿工程 研究方向 岩体力学与岩层控制 答辩委员会主席 谢耀社 评 阅 人 牟宗龙 王卫军 二○一七年五月 学位论文使用授权声明学位论文使用授权声明 本人完全了解中国矿业大学有关保留、使用学位论文的规定，同意本人所撰 写的学位论文的使用授权按照学校的管理规定处理 作为申请学位的条件之一， 学位论文著作权拥有者须授权所在学校拥有学位 论文的部分使用权，即①学校档案馆和图书馆有权保留学位论文的纸质版和电 子版，可以使用影印、缩印或扫描等复制手段保存和汇编学位论文；②为教学和 科研目的，学校档案馆和图书馆可以将公开的学位论文作为资料在档案馆、图书 馆等场所或在校园网上供校内师生阅读、浏览。另外，根据有关法规，同意中国 国家图书馆保存研究生学位论文。 （保密的学位论文在解密后适用本授权书） 。 作者签名 导师签名 年 月 日 年 月 日 致致 谢谢 日月如梭，光阴似箭，三年的研究生求学生涯即将结束，在论文即将完成之 际，首先衷心的感谢导师黄炳香教授三年来对我的培养和帮助。本论文从选题到 最终定稿，每一步都是在导师的悉心指导下完成的，倾注了导师大量的心血。黄 炳香教授渊博的专业知识，严谨的治学态度，精益求精的工作作风，诲人不倦的 高尚师德，严以律己、宽以待人的崇高风范给学生树立起潜移默化的典范作用， 这也是导师传授给学生最宝贵的财富。在此，谨向我的导师致以深深的敬意和衷 心的感谢 在论文完成过程中，得到了刘江伟博士、卢卫永博士、赵兴龙博士在论文总 体思路上的指导和帮助，在此向他们表示衷心的感谢 在论文完成过程中，还得到了张佳兴硕士、田泽础硕士、张权硕士、徐杰硕 士、张新硕士、王常委硕士在物理模拟实验和数据处理方面给予我的帮助，在此 向他们表示诚挚的谢意 特别感谢家人在研究生期间给予我的关怀 感谢所有曾给予我帮助的老师、同学和朋友 感谢所有参考文献的作者 感谢百忙之中评审论文的各位专家、学者 杨 帆 2017 年 5 月 5 日 I 摘 要 摘 要 煤岩体水力致裂技术已广泛应用于煤炭行业， 利用水力致裂技术防治煤与瓦 斯突出以及冲击矿压等方面已取得初步成效。目前，水力致裂期间引起煤岩体应 力的变化规律还不清楚， 对于利用水力致裂技术进行煤矿动力灾害防治而引起的 应力扰动是否会诱导突出和冲击仍具有争议。因此，研究煤岩体水力致裂期间及 致裂之后的应力扰动规律是一项非常迫切且必要的基础性研究。 本文采用物理模 拟实验、数值模拟、理论分析和现场分析等方法对煤岩体水力致裂期间及之后的 应力扰动规律进行研究。 通过在试块内部埋设骨架应力传感器和孔隙水压力传感器， 运用大尺寸真三 轴水力致裂实验系统进行了物理模拟实验， 实时监控了水力致裂过程中水压力的 动态变化，监测了试块内骨架应力的动态变化，研究了水力致裂过程中裂缝周边 的应力及其梯度变化规律，实验结果表明在三个主应力方向上，排量越大，应 力扰动现象越明显；距离致裂钻孔越近，其应力扰动现象越明显；在垂直于主破 裂面方向的应力扰动最为明显，其他方向的应力扰动相对较小。 运用 RFPA2D-FLOW 数值模拟软件对水力致裂的应力扰动规律进行研究， 模 拟结果表明钻孔开裂前，在钻孔周围形成压应力集中，并且随着钻孔水压力的 增大，垂直于最小主应力方向上的应力集中系数逐渐增大，最大主应力方向上的 应力集中系数逐渐减小，并且应力扰动的影响范围逐渐增大；钻孔开裂后，随着 水压裂缝的张开及扩展， 垂直于最小主应力方向的应力集中系数及应力升高区的 范围逐渐增大，并且在水压裂缝尖端形成明显的拉应力集中，使裂尖发生张拉破 坏；距离钻孔越远，水压力对主应力的影响越小，同时应力梯度的变化也越小。 运用弹性力学、水力学、渗流力学及断裂力学进行理论分析，分别从钻孔未 注水时、 钻孔注水未开裂时及钻孔注水开裂后三个阶段计算了钻孔周边和裂缝周 边应力场。 结合燕子山煤矿 8403 工作面水力致裂现场实测数据，选取了 2 个致裂孔数 据进行分析，结果表明在致裂的过程中，在工作面听见多次顶板破裂声，说明 由于水压裂缝的产生及扩展使得工作面内的应力扰动较为明显， 在某个局部形成 较大的应力集中，使煤岩体处于塑性变形范围内，当应力集中超过煤岩体的塑性 极限时，应变能释放，进而煤岩体内的应力向深部转移。 该论文有图 55 幅，表 6 个，参考文献 78 篇。 关键词关键词水力致裂；骨架应力；应力梯度；应力场；应力扰动 II Abstract Hydraulic fracturing technology has been widely used in coal industry. Achievements have been made in preventing and controlling the coal and gas outburst and rock burst by hydraulic fracturing. At present, the variation law of stress disturbance during hydraulic fracturing has not been studied sufficiently. When hydraulic fracturing is pered to eliminate dynamic disasters in coal mine, whether the stress disturbance will lead to coal and gas outburst and rock burst is not clear. Therefore, it is necessary and urgent to investigate the stress disturbance law during and after hydraulic fracturing. In this thesis, laboratory experiments, numerical simulation, theoretical analysis and field analysis are carried out to study the stress disturbance law during and after hydraulic fracturing in coal and rock mass. To study the stress disturbance law during hydraulic fracturing, physical experiments are pered using large size true triaxial hydraulic fracturing experimental system. Frame stress sensors and pore pressure sensors are embedded in the test block in advance. During the experiments, the dynamic variation of water pressure and frame stress are monitored and recorded in real-time. The change law of stress gradient around hydraulic fractures is investigated. Experiment results show that along the three principal stresses, the larger the water injection volume, the greater the stress disturbance, the shorter the distance away from the borehole, the greater the stress disturbance. The stress disturbance in the direction perpendicular to the main hydraulic fracture is the most obvious. In other directions, the stress disturbance is relatively small. Investigation of stress disturbance law during hydraulic fracturing is carried out using RFPA2D-FLOW numerical simulation software. The simulation results indicate that before the initiation of hydraulic fracture, stress concentration occurs around the borehole. With the increase of the borehole water pressure, the stress concentration in the direction perpendicular to the minimum principal stress increases gradually. At the same time, stress concentration in the direction parallel to the minimum principal stress decreases. The range of stress disturbance correspondingly increases. After the initiation of hydraulic fracture, with the opening and propagation of hydraulic fracture, the stress concentration factor and the range of stress-increased area increases gradually in the direction perpendicular to the minimum principal stress. As a result, obvious III stress concentration occurs at the hydraulic fracture tip, leading to the tensile failure of the fracture tip. The further the distance to the borehole, the less the impact of water pressure on the principal stresses decreases is, and correspondingly the smaller the stress gradient variation is. Theoretical analysis is pered on the basis of elastic mechanics, hydraulics, seepage mechanics and fracture mechanics. Stress field around the borehole in different stages of before water injection, before the initiation of the hydraulic fracture and after the initiation of hydraulic fracture are calculated separately. Based on the hydraulic fracturing data measured in 8403 working face in Yanzishan coal mine, hydraulic fracturing data of two fracture boreholes are analyzed. The results show that the sounds of roof fracture were heard many times during hydraulic fracturing, indicating that the stress disturbance caused by the initiation and propagation of hydraulic fractures is obvious and great stress concentration occur at local area. When the stress concentration exceeds the plasticity limitation of the coal and rock mass, the strain energy is released and stress is transferred into the deep area of the coal and rock mass. There are 55 figures, 6 tables and 78 references in this paper. Keywords hydraulic fracturing; frame stress; stress gradient; stress field; stress disturbance IV 目 录 目 录 摘摘 要要............................................................................................................................ I 目目 录录......................................................................................................................... IV 图清单图清单........................................................................................................................ VII 表清单表清单......................................................................................................................... XI 1 绪论绪论............................................................................................................................ 1 1.1 问题的提出 ............................................................................................................. 1 1.2 研究现状及发展趋势 ............................................................................................. 2 1.3 本文研究内容和研究方法 ..................................................................................... 5 2 水力致裂应力扰动的物理模拟实验研究水力致裂应力扰动的物理模拟实验研究 ............................................................... 7 2.1 实验方案 ................................................................................................................. 7 2.2 传感器的参数 ......................................................................................................... 9 2.3 试块的制作 ........................................................................................................... 11 2.4 水压裂缝的扩展特征 ........................................................................................... 15 2.5 最小主应力方向的骨架应力及其梯度变化规律 ............................................... 19 2.6 中间主应力方向的骨架应力及其梯度变化规律 ............................................... 23 2.7 最大主应力方向的骨架应力变化规律 ............................................................... 29 2.8 应力扰动程度分析 ............................................................................................... 30 2.9 本章小结 ............................................................................................................... 31 3 水力致裂应力扰动的数值模拟研究水力致裂应力扰动的数值模拟研究 ..................................................................... 32 3.1 模拟软件简介 ....................................................................................................... 32 3.2 数值模拟方案 ....................................................................................................... 33 3.3 模拟结果分析 ....................................................................................................... 33 3.4 本章小结 ............................................................................................................... 43 4 水力致裂应力扰动的理论分析水力致裂应力扰动的理论分析 ............................................................................. 44 4.1 钻孔未注水时的应力场 ....................................................................................... 44 4.2 钻孔注水未开裂时应力场 ................................................................................... 46 4.3 钻孔注水开裂后的应力场 ................................................................................... 51 4.4 本章小结 ............................................................................................................... 57 5 水力致裂应力扰动的现场分析水力致裂应力扰动的现场分析 ............................................................................. 60 V 5.1 工作面概况 ........................................................................................................... 60 5.2 工作面施工方案 ................................................................................................... 60 5.3 水力致裂过程中的应力扰动分析 ....................................................................... 61 5.4 本章小结 ............................................................................................................... 63 6 结论与展望结论与展望 ............................................................................................................. 64 6.1 主要结论 ............................................................................................................... 64 6.2 展望 ....................................................................................................................... 65 参考文献参考文献 ..................................................................................................................... 66 作者简历作者简历 ..................................................................................................................... 70 学位论文原创性声明学位论文原创性声明 ................................................................................................. 71 学位论文数据集学位论文数据集 ......................................................................................................... 72 VI Contents Abstract ........................................................................................................................ II Contents ..................................................................................................................... VI List of Figures ......................................................................................................... VIII List of Tables ............................................................................................................. XII 1 Introduction ............................................................................................................... 1 1.1 Problem Description ................................................................................................ 1 1.2 Research Status and Development Trend ................................................................ 2 1.3 Research Contents and s .............................................................................. 5 2 Physical Experiments of Stress Disturbance Induced by Hydraulic Fracturing 7 2.1 Experimental Scheme .............................................................................................. 7 2.2 The Parameters of Sensors ....................................................................................... 9 2.3 The Preparation of Test Block ................................................................................ 11 2.4 Crack Propagation Character of Hydraulic Fracture ............................................. 15 2.5 Variation Law of Frame Stress and its Gradient along the Minimum Principal Stress ...................................................................................................................................... 19 2.6 Variation Law of Frame Stress and its Gradient along the Intermediate Principal Stress ............................................................................................................................ 23 2.7 Variation Law of Frame Stress along the Maximum Principal Stress ................... 29 2.8 Analysis of Stress Disturbance Degree .................................................................. 30 2.9 Brief Summary ....................................................................................................... 31 3 Numerical Simulation of Stress Disturbance Induced by Hydraulic Fracturing ...................................................................................................................................... 32 3.1 Introduction to Simulation Software ...................................................................... 32 3.2 Numerical Simulation Scheme .............................................................................. 33 3.3 Analysis of Numerical Simulation Results ............................................................ 33 3.4 Brief Summary ....................................................................................................... 43 4 Theoretical Analysis for Stress Disturbance Induced by Hydraulic Fracturing ...................................................................................................................................... 44 4.1 Stress Field around Borehole before Water Injection ............................................ 44 4.2 Stress Field around Borehole after Water Injection and before Borehole Rupture 46 VII 4.3 Stress Field around Borehole after the Borehole Rupture ..................................... 51 4.4 Brief Summary ....................................................................................................... 57 5 Field Analysis of Stress Disturbance Induced by Hydraulic Fracturing ........... 60 5.1 General Si