本文選題：煤巖體　切入點：水力壓裂　出處：《重慶大學》2014年博士論文　論文類型：學位論文

【摘要】：隨著煤礦開采深度的增加，煤與瓦斯突出危險性不斷增加。對于低滲透性且具有突出危險的煤體，如何有效降低煤與瓦斯突出危險性是亟待解決的重大安全科技問題。煤巖體水力壓裂是低滲透煤體瓦斯抽采、突出煤體消突的有效技術(shù)途徑，尤其是對于單一低滲突出煤體。煤巖體水壓裂縫的擴展及瓦斯運移是決定煤巖體水力壓裂效果的主要因素。為此，本文以煤巖體水壓裂縫擴展及瓦斯運移為主要研究對象，采用理論分析、數(shù)值計算和現(xiàn)場試驗相結(jié)合的方法，系統(tǒng)、深入地研究了煤巖體水力壓裂裂縫擴展及對瓦斯運移影響。本文的主要研究成果與結(jié)論有： ①建立了煤巖體水力壓裂滲流—損傷耦合數(shù)學模型，該模型采用統(tǒng)計方法來表征煤巖體參數(shù)的非均勻性，涉及了滲流場和應力場的耦合作用，內(nèi)含彈—脆性、彈性軟化和彈性弱化3種損傷本構(gòu)，考慮了損傷的演化過程及其對滲透率等物理參數(shù)的影響；提出了該數(shù)學模型的耦合迭代求解算法，并利用Matlab軟件進行有限元編程實現(xiàn)了數(shù)值求解，通過與商業(yè)軟件計算結(jié)果及理論解析解的比較，驗證了該數(shù)學模型及其數(shù)值解法的正確性；系統(tǒng)研究了煤巖體的非均勻性、初始地應力場和鉆孔孔徑對水壓裂縫起裂、擴展的影響，研究了預先水力割縫導向壓裂法和多孔控制壓裂法的水壓裂縫控制機制及影響因素，研究結(jié)果為現(xiàn)場水力壓裂參數(shù)設(shè)計及控制壓裂提供了理論依據(jù)。 ②從水力壓裂驅(qū)趕瓦斯效應、改變瓦斯流態(tài)和影響瓦斯吸附解吸特性三方面研究了煤巖體水力壓裂對瓦斯運移的影響。提出了煤巖體水力壓裂與瓦斯抽采統(tǒng)一數(shù)學模型，，并應用于壓裂后的瓦斯抽采數(shù)值模擬，研究壓裂后的瓦斯運移規(guī)律；數(shù)值計算結(jié)果表明，損傷單元的煤體瓦斯壓力降低明顯，說明水壓裂縫處的煤體透氣性得到改善，形成了新的“更寬闊、通暢”的瓦斯運移通道，顯著提高了瓦斯抽采效果。研究結(jié)果對現(xiàn)場壓裂鉆孔和瓦斯抽采鉆孔布置優(yōu)化具有指導意義。 ③基于煤巖體變形模型、水壓裂縫面內(nèi)流體壓降模型和水壓裂縫擴展模型，建立了低滲透煤巖體水力壓裂單一裂縫擴展數(shù)學模型，提出了該數(shù)學模型的數(shù)值求解算法，并利用APDL二次開發(fā)語言實現(xiàn)了數(shù)值求解。確定了注入壓力、煤巖體彈性模量、初始地應力場以及壓裂液黏度對水力壓裂單一裂縫擴展的影響規(guī)律。研究結(jié)果為現(xiàn)場水力壓裂施工作業(yè)參數(shù)選擇提供理論指導。 ④基于煤體注水難易程度的6個判別指標，構(gòu)建了煤巖體水力壓裂后注水難易程度的Fisher判別模型和可拓判別模型。工程實例判別結(jié)果表明，2種方法的判別結(jié)果與工程勘察分類、模糊聚類法和神經(jīng)網(wǎng)絡(luò)法的結(jié)果一致或更好，實現(xiàn)了壓裂后煤體注水難易程度的科學評價和分類，為水力壓裂后進一步采取靜壓注水措施的可行性判斷提供了參考依據(jù)。 ⑤基于水力壓裂裂縫擴展規(guī)律及其對瓦斯的運移影響理論研究，并兼顧考慮煤礦井下施工條件和瓦斯抽采等制約因素，提出了煤巖體水力壓裂技術(shù)，該技術(shù)集煤巖體增透、瓦斯驅(qū)趕、抽采與注水濕潤于一體。煤巖體水力壓裂現(xiàn)場試驗結(jié)果表明，水壓裂縫的擴展經(jīng)歷了“閉合—張開—產(chǎn)生新裂縫”的過程，隨著壓裂孔與水壓裂縫前沿距離的增大，水壓力沿程衰減，水壓裂縫擴展所需的水壓不斷增大；壓裂后的考察鉆孔和壓裂鉆孔中的瓦斯?jié)舛仍黾�，驗證了水力壓裂的驅(qū)趕瓦斯效應。現(xiàn)場瓦斯抽采和突出預測指標結(jié)果表明，壓裂鉆孔的瓦斯抽采濃度和抽采純量呈現(xiàn)“高—低—高”的特點；壓裂影響范圍內(nèi)的突出危險性預測指標值均未超標，驗證了煤巖體水力壓裂對瓦斯運移的影響理論，即水力壓裂技術(shù)可有效增大煤巖體的透氣性，提高瓦斯抽采率和消除煤與瓦斯突出危險性，并具有顯著的技術(shù)經(jīng)濟效益。
[Abstract]:With the increase of mining depth, increasing the risk of coal and gas outburst. With coal outburst danger for low permeability and how to reduce the risk of coal and gas outburst is a major security technology problem to be solved. The hydraulic fracturing of coal rock is the extraction of coal gas in low permeability, effective method of outburst coal the body of outburst, especially for single low permeability outburst coal. Expansion and gas migration in coal and rock mass hydraulic fracture is a major factor in determining the effect of hydraulic fracturing of coal and rock. Therefore, the extension of hydraulic fracture of coal and rock and gas migration as the main research object, using theoretical analysis, system method, numerical calculation and field test the combination of the in-depth study of the coal rock mass hydraulic fracturing crack propagation and the influence on gas migration. The main research results and conclusions:
Firstly, the coupled mathematical model of hydraulic fracturing of coal rock mass seepage damage, non uniformity of the model adopts the statistical method to characterize the coal rock mass parameters, involving the coupling effect of seepage field and stress field, including elastic brittle, elastic softening and weakening of 3 kinds of elastic damage constitutive, considering the damage evolution process and the effect on the permeability of the physical parameters; the coupling iterative algorithm of the mathematical model, and finite element programming numerical solution by using Matlab software. By comparing the results and analytical solution with commercial software, verifies the correctness of the mathematical model and numerical solution; non uniformity of coal rock mass, initial stress and hole of hydraulic fracturing, the influence of expansion, pre fracturing and hydraulic slotting guide porous control fracturing fracture water control The mechanism and influencing factors are used to provide theoretical basis for the design of field hydraulic fracturing parameters and the control of fracturing.
The methane driven hydraulic fracturing effect, change the gas flow and effect of gas adsorption and desorption characteristics of the three aspects of the influence of coal rock mass hydraulic fracturing of gas migration is proposed. The coal rock mass hydraulic fracturing and gas drainage unified mathematical model, numerical simulation of gas production after fracturing and applied to the study of gas migration law after fracturing; the numerical results show that the coal gas pressure damage unit was significantly reduced, indicating the coal pressure crack permeability is improved, the formation of a new "broad channel of gas migration smoothly, significantly improves the gas drainage effect. The results of drainage borehole layout optimization has guiding significance on the field of fracturing drilling and gas.
Based on the coal rock deformation model, hydraulic fracture plane pressure drop model and hydraulic crack propagation model was established for low permeability coal rock hydraulic fracturing single crack propagation mathematical model, put forward the numerical algorithm of the mathematical model, and use APDL two development language is employed. To determine the injection pressure, coal and rock influence of elastic modulus, initial stress field and the viscosity of fracturing fluid for hydraulic fracturing of single crack propagation. The results for the hydraulic fracturing operation parameters provide theoretical guidance.
The coal injection to 6 degree discriminant index based on construction of the coal rock mass hydraulic fracturing after injection of the degree of difficulty of Fisher discriminant model and extension discriminant model. Results the engineering example shows that the results of 2 methods and engineering classification, fuzzy clustering method and neural network method is consistent with the result or better and realized after fracturing coal injection to the scientific evaluation of degree and classification, provides a reference to determine the feasibility of hydraulic fracturing after taking further measures the static pressure water injection.
The propagation of hydraulic fractures based on the theory and Research on the effects of the gas migration, taking into account the factors considered in coal mine construction conditions and gas drainage, put forward the coal rock mass hydraulic fracturing technology, the technology of coal rock mass permeability, gas drive, drainage and water injection in one wet coal rock mass hydraulic fracturing site. Tests show that the expansion of hydraulic fracture through the process of closed - Open - new cracks ", with the increase of hydraulic fracturing hole and crack front distance, water pressure attenuation, hydraulic crack propagation required water pressure increases; increasing gas concentration after fracturing and fracturing borehole drilling investigation and verification the effect of methane driven fracturing. Mining and outburst prediction index results show that pumping site gas drainage and mining, concentration of pure quantity showed a" high low high "special gas fracturing drilling Point; outburst prediction of fracturing effect within the scope of the index did not exceed the standard, the influence of gas migration in coal rock hydraulic fracturing theory test, permeability that hydraulic fracturing technology can effectively increase the coal mass and improve the gas drainage rate and eliminate the danger of coal and gas outburst, and has remarkable technical and economic benefits.

【學位授予單位】：重慶大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TD712

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