基于嵌入式网格的裂缝性致密油储层压裂生产一体化的数值模拟
Integrated Numerical Simulation Method for Fracturing and Production of Fractured Tight Oil Reservoirs Based on Embedded Mesh
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摘要: 有效的一体化模拟裂缝性致密油储层压裂生产过程是评价压裂设计的关键之一。基于嵌入式网格的基质裂缝全域空间流固耦合数值模拟方法, 考虑天然裂缝影响下裂缝动态扩展、低速非线性渗流、基质与裂缝应力敏感, 实现裂缝性致密油储层压裂生产一体化多机理模拟。分析天然裂缝、非线性渗流对裂缝扩展及生产动态的一体化影响规律。模型可以在生产过程中任意时刻模拟压裂, 为重复压裂、加密井的设计分析提供有效的工具。当基质岩石的抗拉强度由10.2 MPa降到2.3 MPa时, 破碎带逐渐增大, 滤失作用增加, 导致主裂缝长度降低8%~9%, 但可以增加累产油量17.5%至61.1%, 影响作用显著且主要影响早期的日产油量。与启动压力梯度模型相比, 低速非线性渗流可以更好地预测致密油生产动态。该方法可为裂缝性致密油储层压裂生产一体化的动态预测、规律分析、工艺优化提供高效的工具。Abstract: Efficiently integrated simulation of the fracturing production process of fractured tight oil reservoirs is one of keys to evaluate fracturing design. In this paper, a full-space hydro-geomechanics coupling numerical simulation method of matrix fractures based on embedded grids is adopted. We further consider the dynamic fracture propagation under the influence of natural fractures, low-velocity nonlinear flow, and the stress sensitivity effect of matrix and fractures. The integrated multi-mechanism simulation of fracturing production in fractured tight oil reservoirs is achieved. Then the integrated influence of natural fractures and nonlinear flow on fracture propagation and production performance is analyzed. The research results show that our model can simulate fracturing at any time during production, providing an effective tool for the design and analysis of refracturing and infill wells. When the tensile strength of the matrix rock decreases from 10.2 MPa to 2.3 MPa, the damage zone gradually increases and the fluid leak-off increases, resulting in a decrease of the main fracture length by 8%~9%. However, it can increase the cumulative oil production by 17.5% to 61.1%. The impact is significant and mainly affects the early daily oil production. Low-velocity nonlinear flow can better predict tight oil production performance than the threshold pressure gradient model. Our proposed method provides an efficient tool for integrated dynamic prediction, effect analysis, and optimization of fracturing production in fractured tight oil reservoir.