本文選題：井下水力壓裂 + 應力場��； 參考：《中國礦業(yè)大學》2013年博士論文

【摘要】：論文針對井下煤層水力壓裂過程中濾失率引起的煤體水分增加對瓦斯運移的負效應以及“瓦斯場、滲流場、應力場”重新分布規(guī)律問題，采用理論分析、數值模擬、實驗室實驗和現場工業(yè)性試驗相結合的方法，分析了不同煤體結構適應性的井下水力壓裂技術，研究了煤-水-氣三相介質條件下瓦斯解吸規(guī)律，揭示了水力壓裂影響區(qū)域地應力分布特征，探討了水力壓裂煤層瓦斯運移產出的雙重效應，指出了利用瞬變電磁法和示蹤劑法對井下煤層水力壓裂流場分布特征研究和評價的可行性。 （1）煤-水-氣三相介質條件下瓦斯解吸規(guī)律的實驗/試驗研究表明，煤樣含水率越高，累計解吸量越少、瓦斯解吸速率越低；ΔP、q、K13個指標值隨煤體含水率的增大而減小。說明水分對瓦斯解吸運移不但有抑制作用，同時還揭示出含水狀態(tài)下所測試的校檢指標，掩蓋了煤與瓦斯突出危險性。 （2）井下單孔水力壓裂數值模擬表明，壓裂孔兩側本來的應力升高區(qū)域地應力大大降低，很大范圍內地應力都降低到低狀體，鉆孔兩側及Z方向煤體發(fā)生位移；現場水力壓裂影響區(qū)鉆屑量的變化特征，反映了壓裂后集中應力帶向煤體深部轉移，采掘工作面卸壓帶長度增大，鉆屑量變化響應的工作面應力分布狀態(tài)，與壓裂影響區(qū)應力場特征數值模擬結果一致；通過數值模擬同時也發(fā)現了水力壓裂的不足之處，，在裂縫尖端也產生了新的應力集中。 （3）針對煤層賦存地質條件的復雜性和非均質性，以及水力壓裂研究過程中出現的壓裂液流場短路、裂隙擴展分布不均、單孔尖端應力集中等現象，提出了“雙孔（多孔）均勻壓裂、定向鉆進控制壓裂、水力噴射輔助壓裂、預先水力割縫導向壓裂、開楔形環(huán)槽定向壓裂”5種用于實現煤層整體、均勻壓裂的優(yōu)化工藝。 （4）利用流態(tài)判識標準雷諾數Re和啟動壓力梯度λ，對水力壓裂增透加速瓦斯產出的正效應，以及煤體水分增大抑制瓦斯運移負效應的研究表明，含水率并不是影響啟動壓力梯度的主要因素，當煤層滲透率增大到一定程度，啟動壓力梯度就將消失，揭示了對于透氣性較好的高滲煤層，水分的增加對瓦斯抽采的影響是有限的，水力壓裂增透加速瓦斯抽采的本質是改變了瓦斯在煤層內流態(tài)，與壓裂過程中壓裂液濾失引起的負效應相比，壓裂增透產生的正效應對瓦斯運移產出起控制作用。 （5）針對在評價壓裂流場分布特征（滲流能力、影響范圍、均勻程度）方面存在的難題，構建了含瓦斯煤體水力壓裂流場評價數學模型，開展了基于瞬變電磁法和示蹤劑跟蹤法的水力壓裂流場分布特征理論和實驗研究，豐富了井下水力壓裂評價的方法和手段，對提高現場施工質量、減小施工風險有很大應用價值。
[Abstract]:Aiming at the negative effect of the increase of coal body moisture on gas migration and the redistribution of gas field, seepage field and stress field in the process of hydraulic fracturing in underground coal seam, theoretical analysis and numerical simulation are used in this paper. Combining the laboratory experiment with the field industrial test, the underground hydraulic fracturing technology with different coal structure adaptability is analyzed, and the gas desorption law under the condition of coal-water-gas three-phase medium is studied. The distribution characteristics of in-situ stress in the area affected by hydraulic fracturing are revealed, and the dual effect of gas migration and production in hydraulic fracturing coal seam is discussed. The feasibility of using transient electromagnetic method and tracer method to study and evaluate the distribution characteristics of hydraulic fracturing flow field in underground coal seam is pointed out. (1) the experimental and experimental study on the law of gas desorption under the condition of coal-water-gas three-phase medium shows that; The higher the moisture content of coal sample is, the less the cumulative desorption amount is, and the lower the gas desorption rate is; The results show that water can not only restrain the gas desorption migration, but also reveal the check index of the gas desorption and migration under the condition of water content, and cover up the danger of coal and gas outburst. (2) the numerical simulation of hydraulic fracturing in single hole shows that The in-situ stress on both sides of the fracturing hole has been greatly reduced, the in-situ stress has been reduced to a low body in a wide range, the displacement occurred on both sides of the borehole and the Z direction coal body, and the variation characteristics of the cuttings amount in the affected area of hydraulic fracturing, The results show that the stress distribution state of the coal face after fracturing is the same as the numerical simulation results of stress field characteristics in the area affected by fracturing, where the length of pressure relief zone increases and the response of cuttings quantity changes after fracturing. At the same time, the shortage of hydraulic fracturing is found by numerical simulation, and a new stress concentration is also produced at the fracture tip. (3) aiming at the complexity and heterogeneity of the geological conditions of coal seam occurrence, As well as the phenomena such as short circuit of fracturing fluid flow field, uneven distribution of fracture propagation, stress concentration at the tip of single hole and so on in the process of hydraulic fracturing, it is proposed that "double hole (porous) uniform fracturing, directional drilling control fracturing, hydraulic jet assisted fracturing, etc." In advance hydraulic fracturing and directional fracturing with wedge ring groove "5 kinds of fracturing are used to realize the whole of coal seam." Optimization technology of uniform fracturing. (4) by using Reynolds number and starting pressure gradient 位, the positive effect of hydraulic fracturing on accelerating gas production and the negative effect of increasing coal moisture on gas migration are studied. Water cut is not the main factor affecting the starting pressure gradient. When the permeability of coal bed increases to a certain extent, the starting pressure gradient will disappear. The effect of water increase on gas drainage is limited. The essence of hydraulic fracturing and accelerating gas drainage is to change the gas flow state in coal seam, compared with the negative effect caused by fracturing fluid filtration during fracturing. The positive effect of anti-permeability fracturing plays a controlling role in gas migration and production. (5) in order to evaluate the distribution characteristics of fracturing flow field (seepage ability, influence range, uniformity), The mathematical model of flow field evaluation for gas-bearing coal body hydraulic fracturing is established, and the theory and experimental research on the distribution characteristics of hydraulic fracturing flow field based on transient electromagnetic method and tracer tracking method are carried out, which enriches the methods and means of underground hydraulic fracturing evaluation. It has great application value to improve the construction quality and reduce the construction risk.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TD825;TD712

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