Fractures control fluid flow, solute transport, and mechanical deformation in crystalline media. They can be modeled numerically either explicitly or implicitly via an equivalent continuum. The implicit framework implies lower computational cost and complexity. However, upscaling heterogeneous fracture properties for its implicit representation as an equivalent fracture layer remains an open question. In this study, we propose an approach, the Equivalent Fracture Layer (EFL), for the implicit representation of fractures surrounded by low-permeability rock matrix to accurately simulate hydromechanical coupled processes. The approach assimilates fractures as equivalent continua with a manageable scale (≫1 μm) that facilitates spatial discretization, even for large-scale models including multiple fractures. Simulation results demonstrate that a relatively thick equivalent continuum layer (in the order of cm) can represent a fracture (with aperture in the order of μm) and accurately reproduce the hydromechanical behavior (i.e., fluid flow and deformation/stress behavior). There is an upper bound restriction due to the Young's modulus because the equivalent fracture layer should have a lower Young's modulus than that of the surrounding matrix. To validate the approach, we model a hydraulic stimulation carried out at the Bedretto Underground Laboratory for Geosciences and Geoenergies in Switzerland by comparing numerical results against measured data. The method further improves the ability and simplicity of continuum methods to represent fractures in fractured media.

中文翻译：

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使用连续体方法对裂缝进行隐式流体力学表示


裂缝控制结晶介质中的流体流动、溶质输送和机械变形。它们可以通过等效连续体显式或隐式地进行数值建模。隐式框架意味着较低的计算成本和复杂性。然而，放大异质裂隙属性以将其隐含表示为等效裂隙层仍然是一个悬而未决的问题。在本研究中，我们提出了一种方法，等效断裂层 （EFL），用于隐含表示被低渗透性岩石基质包围的裂缝，以准确模拟流体力学耦合过程。该方法将裂缝同化为等效连续体，具有可管理的尺度 （≫1 μm），便于空间离散化，即使对于包括多条裂缝的大规模模型也是如此。仿真结果表明，相对较厚的等效连续层（厘米量级）可以表示裂缝（孔径约为 μm）并准确再现流体力学行为（即流体流动和变形/应力行为）。由于杨氏模量存在上限限制，因为等效断裂层的杨氏模量应低于周围基体的杨氏模量。为了验证该方法，我们通过将数值结果与测量数据进行比较，对在瑞士 Bedretto 地球科学和地质能源地下实验室进行的液压增产进行了建模。该方法进一步提高了连续体方法在裂隙介质中表示裂隙的能力和简单性。