Abstract In this paper, we describe an efficient modeling approach, named embedded discrete fracture method (EDFM), for incorporating arbitrary 3D, discrete fractures, such as hydraulic fractures or faults, into modeling fracture-dominated fluid flow and heat transfer in fractured geothermal reservoirs. This technique allows 3D discrete fractures to be discretized independently from surrounding rock volume and inserted explicitly into a primary fracture/matrix grid, generated without including 3D discrete fractures in prior. An effective computational algorithm is developed to discretize these 3D discrete fractures and construct local connections between 3D fractures and fracture/matrix grid blocks representing the surrounding rock volume. The constructed gridding information on 3D fractures is then added to the primary grid. This embedded fracture modeling approach can be directly implemented into a developed geothermal reservoir simulator via the integral finite difference (IFD) method or with TOUGH2 technology. This embedded fracture modeling approach is very promising and computationally efficient to handle realistic 3D discrete fractures with complicated geometries, connections, and spatial distributions. Compared with other fracture modeling approaches, it avoids cumbersome 3D unstructured, local refining procedures, and increases computational efficiency by simplifying Jacobian matrix size and sparsity, while maintaining enough accuracy. Several numeral simulations are presented to demonstrate the utility and robustness of the proposed technique. Our numerical experiments show that this approach captures all the key patterns about fluid flow and heat transfer dominated by fractures in these cases. Thus, this approach is readily available to the simulation of fractured geothermal reservoirs with both artificial and natural fractures.

中文翻译：

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用于模拟地热储层中以裂缝为主的流体流动和传热的嵌入式 3D 裂缝建模方法

摘要 在本文中，我们描述了一种名为嵌入式离散裂缝方法 (EDFM) 的有效建模方法，用于将任意 3D 离散裂缝（例如水力裂缝或断层）结合到裂缝性地热储层中以裂缝为主的流体流动和传热的建模中。 . 该技术允许 3D 离散裂缝独立于围岩体积进行离散化，并明确插入到原始裂缝/矩阵网格中，生成时不包括先前的 3D 离散裂缝。开发了一种有效的计算算法来离散这些 3D 离散裂缝，并在 3D 裂缝和代表围岩体积的裂缝/矩阵网格块之间构建局部连接。然后将构建的关于 3D 裂缝的网格信息添加到主网格中。这种嵌入式裂缝建模方法可以通过积分有限差分 (IFD) 方法或 TOUGH2 技术直接实施到开发的地热储层模拟器中。这种嵌入式裂缝建模方法在处理具有复杂几何形状、连接和空间分布的真实 3D 离散裂缝方面非常有前途且计算效率高。与其他裂缝建模方法相比，它避免了繁琐的 3D 非结构化、局部细化程序，并通过简化雅可比矩阵大小和稀疏性来提高计算效率，同时保持足够的精度。提出了几个数字模拟来证明所提出的技术的实用性和鲁棒性。我们的数值实验表明，这种方法捕获了在这些情况下由裂缝主导的流体流动和传热的所有关键模式。因此，这种方法很容易用于模拟具有人工和天然裂缝的裂缝性地热储层。