压裂液作用下煤体软化性及水压裂缝扩展规律研究.pdf

论文题目压裂液作用下煤体软化性及水压裂缝扩展规律研究 工程领域矿业工程 硕 士 生刘 冬（签名） 指导教师邓广哲（签名） 摘要 煤层水力致裂软化技术工艺，是通过压裂和软化作用途径，达到预先弱化顶煤的目 的，是一项煤矿安全高效开采的保障技术。本文以小红沟煤矿急倾斜煤层顶煤注水软化 工程为背景，针对小红沟主采煤层B1、B2，采用理论分析、实验研究、数值模拟和现场 试验等研究方法，得到以下主要结论 对B1、B2两种煤样进行了水理性试验，依据煤样亲水试验和大煤样裂隙统计的结 果，判断出B1煤样较B2煤样破碎，且孔隙多属于开裂隙，表明B1煤样较B2煤样易于 软化；通过不同压裂液亲水性试验，结合软化性判据，得出不同压裂液的软化性能为第 二种第四种第一种第三种清水。 对压裂液浸泡后的饱和煤样进行单轴压缩试验和超声波试验，试验结果表明，与自 然状态相比较， 除个别煤样试件外， 压裂液作用下试件力学参数均受到不同程度的弱化， 即压裂液对煤样具有软化性作用，但软化效果不同，依据试验结果，给出了压裂液作用 下煤样损伤演化变量和本构模型。 建立了基质力学参数弱化模型和基质非均质模型，运用 F-RFPA 软件模拟压裂液作 用下圆孔水压裂缝扩展，模拟结果表明，与自然状态相比，受压裂液浸泡过的试件， 裂 缝更容易起裂和扩展，裂缝扩展面较为粗糙，分叉裂缝形成的时间较短，数量也较多， 且最终形成的主裂缝与垂直方向夹角较大，此外，通过声发射可以得出受压裂液浸泡过 的试件能量释放要缓慢的多，即损伤是一个渐变的过程。 对小红沟B12煤层顶煤的冒放性进行评价，得出顶煤冒放性差，从煤层强度、赋存 深度入手，揭示出压裂液提高顶煤冒放性的机理。将研究成果应用于急倾斜坚硬顶煤综 放开采中，实践结果表明提高了顶煤冒放性，增加了回采率。 关 键 词压裂液；软化性；裂缝扩展；煤层注水；冒放性 研究类型应用研究 SubjectSubjectSubjectSubjectResearchResearchResearchResearchononononcoalcoalcoalcoal softeningsofteningsofteningsoftening andandandand hydraulichydraulichydraulichydraulic fracturingsfracturingsfracturingsfracturings expandingexpandingexpandingexpanding underunderunderunder facturingfacturingfacturingfacturing fluidfluidfluidfluid projectprojectprojectproject fieldsfieldsfieldsfields MiningMiningMiningMining EngineeringEngineeringEngineeringEngineering NameNameNameName LiuLiuLiuLiu DongDongDongDongSignatureSignatureSignatureSignature InstructorInstructorInstructorInstructor DengDengDengDeng GuangzheGuangzheGuangzheGuangzheSignatureSignatureSignatureSignature ABSTRACT Coal seam hydraulic crack softening technologies，isthrough the fracturing and softening action ways，and to the purpose of the top-coalisweakening in advance,is a coal mine safety guaranteeofmining technology. Based on Xiao honggou water injection softening as project background, in view of Xiao honggouB12coal seam,using theoretical analysis and experimental research, numerical simulation and field test of research s, We obtained the following conclusions We conducted a hydrophilic test ofB1andB2, according to the results of the coal sample water test and the coal sample fracture statistics, we determineB1coal samples more broken compared to theB2samples,and the pores are mostly open cracks, indicating that theB1 coalkind of coal than theB2sampleiseasy to soften; According to different fracturing fluid hydrophilic test, combinedwithsoftening criterion, we determine the softening properties of the fracturing fluidthe second fourthfirst third. After immersionofthe fracturing fluid saturated coal samples for uniaxial compression testsand ultrasonic tests,testresults show that compared with the natural state, except the coal sample specimen, the specimen fracturing fluid under the action of mechanical parameters are subject to varying degreesweakening of the fracturing fluid,ithas a softening effect of the coal sample, but to soften the effect, Based on thetestresult, we give the damage evolution variables and two constitutive model under fracturing fluid Using F-RFPA software simulation of fracturing fluid under the action of water pressure onhole crack, that was based on matrix mechanics parameters attenuation model and matrix heterogeneity the model.Because of the pressureoffracturing fluid effect of coal and the natural state of coal physical parameters and homogeneous degree coefficient assignmentis different, compared with the natural state, under the action of external force, coal under fracturing fluid,iseasier to crack initiation and propagation of cracks, crack surfaceisrough, bifurcated crack ing timeisshort, amountismore also, and eventually ed the main crack and vertical included angleisbigger, moreover, energycanrelease much slower, i.e. injuryisa gradual process. B12coal seam top-coal cavingisuated, we know that top-coal cavingispoor; Proceed with coal seam strength,miningdepth, we reveal mechanism of the fracturing fluid to raise the top coal caving.Research results in steep hard top coal caving mining, the results show thatitcan increase top coal caving and the recovery rate. KeyKeyKeyKey wordswordswordswordsfacturing fluid;Softening;crack propagation; Seam water injection; caving ability ThesisThesisThesisThesis Application Research 目录 I 目录 1 1 1 1 绪论绪论......................................................................................................................................... 1 1.1 选题的背景和意义...........................................................................................................1 1.1.1 选题的背景.................................................................................................................1 1.1.2 选题的意义.................................................................................................................2 1.2 国内外研究现状...............................................................................................................2 1.2.1 压裂液技术.................................................................................................................2 1.2.2 岩石破裂过程的化学-应力耦合...............................................................................3 1.2.3 水压裂缝扩展.............................................................................................................5 1.3 本文的主要工作...............................................................................................................6 1.3.1 研究目标.....................................................................................................................6 1.3.2 研究的主要内容.........................................................................................................6 1.3.3 技术路线.....................................................................................................................8 2 2 2 2 水煤物理化学作用机理分析水煤物理化学作用机理分析................................................................................................. 9 2.1 增强煤体内破坏的物理化学特征...................................................................................9 2.2 水煤体物理力学损伤机理.............................................................................................10 2.2.1 水对煤体强度的影响机理.......................................................................................10 2.2.2 水对煤体微观强度弱化的机理...............................................................................11 2.3 水煤化学作用的理论分析.............................................................................................11 2.3.1 煤体水化学损伤的化学成分分析理论...................................................................12 2.3.2 煤体水化学损伤的能量分析理论...........................................................................13 2.4 压裂液推动水压裂缝扩展理论....................................................................................13 2.4.1 内压作用裂隙扩展机理...........................................................................................13 2.4.2 水化学损伤对煤体裂隙作用规律...........................................................................14 2.5 小结.................................................................................................................................15 3 3 3 3 压裂液作用下煤体水理性试验压裂液作用下煤体水理性试验........................................................................................... 71 3.1 室内试验设计.................................................................................................................17 3.1.1 压裂液配制...............................................................................................................17 3.1.2 煤样制备...................................................................................................................17 3.1.3 浸泡试验...................................................................................................................18 目录 II 3.2 煤样结构........................................................................................................................18 3.2.1 大煤样裂隙测定.......................................................................................................18 3.2.2 煤样孔隙率及含水率测定.......................................................................................19 3.3 不同压裂液亲水性试验.................................................................................................21 3.3.1 吸水率测定...............................................................................................................21 3.3.2 水煤接触角...............................................................................................................23 3.4 煤层注水软化难易性分析.............................................................................................26 3.4.1 煤层注水软化性判据...............................................................................................26 3.4.2 煤层软化性测定结果...............................................................................................27 3.5 不同压裂液软化性能分析.............................................................................................28 3.6 小结.................................................................................................................................31 4 4 4 4 压裂液作用下煤体宏观力学试验与本构模型压裂液作用下煤体宏观力学试验与本构模型...................................................................32 4.1 试验准备.........................................................................................................................32 4.2 压裂液饱和煤样单轴压缩破裂过程试验及规律分析.................................................32 4.2.1 试验过程...................................................................................................................32 4.2.2 煤样试件破裂全过程试验结果...............................................................................33 4.2.3 压裂液作用下煤样峰值力学特性及机理分析.......................................................33 4.3 压裂液对煤体力学参数影响及机理分析.....................................................................34 4.3.1 实验设备及原理.......................................................................................................34 4.3.2 数据采集...................................................................................................................36 4.3.3 压裂液作用下纵波波速的变化...............................................................................38 4.3.4 压裂液对煤样弹性模量的影响...............................................................................39 4.3.5 压裂液对煤样剪切模量的影响...............................................................................39 4.4 压裂液对煤样宏观力学性能的影响机制.....................................................................40 4.5 压裂液作用下煤样单轴压缩损伤演化变量及本构模型.............................................41 4.5.1 自然状态下煤样损伤演化变量及本构模型...........................................................41 4.5.2 压裂液作用下煤样损伤演化变量及本构模型.......................................................42 4.6 小结.................................................................................................................................44 5 5 5 5 压裂液作用下圆孔水压裂缝扩展规律研究压裂液作用下圆孔水压裂缝扩展规律研究.......................................................................45 5.1 考虑水煤物理化学作用的数值模拟方法.....................................................................45 5.1.1 基质力学参数弱化模型...........................................................................................45 5.1.2 基质非均质模型.......................................................................................................45 目录 III 5.2 考虑水煤物理化学作用数值模拟方案.........................................................................46 5.3 压裂液作用下水压裂缝扩展的数值模拟.....................................................................47 5.3.1 裂缝扩展的宏观过程...............................................................................................48 5.3.2 裂缝扩展的损伤演化过程.......................................................................................50 5.3.3 裂缝扩展形态...........................................................................................................52 5.4 小结.................................................................................................................................53 6 6 6 6 工程实践工程实践............................................................................................................................... 55 6.1 试验条件.........................................................................................................................55 6.2 顶煤冒放性影响因素.....................................................................................................55 6.3 顶煤冒放性评价.............................................................................................................56 6.3.1 煤层强度对顶煤冒放性的影响...............................................................................56 6.3.2 节理裂隙对顶煤冒放性的影响...............................................................................56 6.3.3 煤层赋存深度对顶煤冒放性的影响.......................................................................57 6.4 压裂液提高顶煤冒放性分析.........................................................................................58 6.4.1 煤层强度...................................................................................................................58 6.4.2 赋存深度...................................................................................................................59 6.5 现场试验.........................................................................................................................60 6.5.1 煤层软化的可行性分析...........................................................................................60 6.5.2 煤层注水参数...........................................................................................................61 6.5.3 试验...........................................................................................................................62 6.6 小结.................................................................................................................................62 7 7 7 7 结论与展望结论与展望........................................................................................................................... 64 7.1 主要结论.........................................................................................................................64 7.2 展望.................................................................................................................................65 致谢致谢.......................................................................................................................................... 66 参考文献参考文献.................................................................................................................................. 67 附录附录.......................................................................................................................................... 71 1 绪论 1 1 绪论 1.1 选题的背景和意义 1.1.1 选题的背景 根据 2008 中国可持续发展战略报告 ， 到 2010 年煤炭在一次性能源生产和消费中 将占 70％左右；到 2050 年，煤炭所占比例不会低于 50％。这说明煤炭在相当长一段时 间内还将作为主要能源形式存在。可以预见，煤炭工业在国民经济中的基础地位，将是 长期的和稳固的，具有不可替代性[1]。 急倾斜煤层总的储量和历年产量在我国占 5左右，矿井数量众多。我国大部分矿 区急倾斜煤层煤质优良， 具有很高的开采价值， 对区域经济的发展起到重要的支撑作用。 急倾斜特厚煤层通常采用巷柱式采煤方法，开采效率非常低。急斜煤层水平分段放顶煤 开采技术与顶煤弱化是相伴而生共同发展的，早在上世纪八十年代中期就在窑街二矿、 乌鲁木齐六道湾煤矿和辽源梅河三井开始了急倾斜特厚煤层放顶煤采煤方法的研究， 并 获得了现场工业性试验成功。该采煤方法具有安全、高效、环保等特点，同时对于煤层 厚度变化及地质构造的适