低渗透砂砾岩油藏水力压裂裂缝扩展机理及其数值模拟研究，对该类储层压裂改造成功实施具有重要意义。将砂砾岩储层中砾石表征为基质-交界面-砾石的三模态结构，假定砾石分布与几何尺寸及储层物性满足随机分布，结合Moter-Carolo方法，完成砂砾岩储层数学表征；考虑储层渗流场、应力场、水化膨胀湿度场的三相耦合特征，结合损伤力学、断裂力学等原理，利用细观损伤有限元的方法，建立了砂砾岩储层水力压裂裂缝扩展数学模型，并进行数值模拟研究。模拟分析了不同主应力差、基质-砾石交界面强度、砾石强度情况下，水力裂缝遇砾石扩展情况，并最终实现砂砾岩储层水力裂缝动态扩展数值模拟。研究表明，水力裂缝遇砾发生绕砾、穿砾、止裂现象，并以绕砾扩展为主，且裂缝发生明显转向，存在羽状次生裂缝；裂缝转向程度和裂缝延伸长度与主应力差、砾石强度以及交界面强度有关，主要表现有：水平主应力差越小，水力裂缝遇砾转向越明显；基质-砾石交界面强度增加，水力裂缝明显变短，并难以转向；随着砾石强度的增大，裂缝的转向程度增大。%The numerical simulation on hydraulic fracture propagation in low permeability glutenite oil reservoir is of great sig-niifcance to the successful fracturing stimulation of this reservoir. By characterizing the gravel in the glutenite reservoir as a matrix-interface-gravel three modal textures, and assuming that the gravel distribution, geometry and reservoir property meet the random distribution, the mathematical characterization of glutenite reservoir was completed with the Moter-Carolo method. Taking into account the tri-phase coupling of reservoir seepage ifeld, stress ifeld and hydration propagation moisture ifeld, and according to the principles of damage mechanics and fracture mechanics, the microscopic damage ifnite element method was used to establish a mathematical model of hydraulic fracture propagation in glutenite reservoir. This mathematical model was used to simulate and analyze the hydraulic fracture propagation when the fractures encounter gravels under different principal stress differences, matrix-gravel interface strengths and gravel strengths. Finally, numerical simulation of dynamic propagation of hydraulic fractures in glutenite reservoir was completed. The study results show that some phenomena such as bypassing, passing through and arresting occur when hydraulic fracture encounters gravels. Especially, propagation through bypassing gravel predominates. The fracture apparently diverts, and pinnate secondary fractures occur. The fracture diverting level and penetration are related to the principal stress difference, gravel strength and interface strength. Essen-tially, the smaller the horizontal principal stress, the more apparent the diversion of hydraulic fracture when it encounters gravels. As the matrix-gravel interface strength increases, the hydraulic fracture apparently shortens and is dififcult to divert. As the gravel strength increases, the diverting level of fractures increases.
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