Fluid flow in subsurface tight reservoirs containing pores, microcracks and macrocracks is notably influenced by the characteristics of macro/micro-cracks. A novel hybrid multiscale model is proposed to address the response of macrocracks and pores/microcracks in different spatial scales. Specifically, an equivalent macroscopic model (EMM) deduced from locally periodic representative element volume (REV) is developed using the asymptotic homogenization method to represent the poroelastic behavior of porous medium with microcracks. Simultaneously, the macrocracks are modeled explicitly using the discrete fracture model (DFM), where the hydraulic properties of cracks influenced by fluid pressure gradient is represented by the nonlinear opening/closure behavior. The obtained hybrid model takes into account the heterogeneous nature of fractured rock masses containing pores, micro/macro-cracks, which is fundamental to describe fluid flow behavior in fracture-matrix system. Specialized finite elements, regular meshing technique and adaptive time stepping algorithm are adopted to improve the computational efficiency. The hybrid multiscale model is firstly validated step by step to demonstrate the accuracy and then used to simulate fluid flow in fractured rock reservoir, shedding light on the underlying mechanisms of the enhanced flow capacity resulting from microcrack distribution, connectivity, and macrocrack stimulation.

中文翻译：

---

使用离散裂隙网络均质化方法的裂隙岩石中流体流动的混合多尺度模型


在包含孔隙、微裂纹和宏观裂纹的地下致密储层中，流体流动受到宏观/微观裂缝特性的显著影响。提出了一种新的混合多尺度模型来解决不同空间尺度下宏观裂纹和孔隙/微裂纹的响应。具体来说，使用渐近均质化方法开发了从局部周期性代表元素体积 （REV） 推导出的等效宏观模型 （EMM），以表示具有微裂纹的多孔介质的多孔弹性行为。同时，使用离散断裂模型 （DFM） 对宏观裂纹进行显式建模，其中受流体压力梯度影响的裂纹的水力特性由非线性开/闭行为表示。获得的混合模型考虑了包含孔隙、微观/宏观裂纹的裂隙岩体的非均质性，这是描述裂隙-基质系统中流体流动行为的基础。采用专用有限元、规则网格划分技术和自适应时间步进算法来提高计算效率。首先逐步验证混合多尺度模型以证明其准确性，然后用于模拟裂隙岩储层中的流体流动，阐明了微裂纹分布、连通性和宏观裂纹增产导致流动能力增强的底层机制。