发表机构
Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
提出基于裂纹几何演化的渗透率模型，在GeoDyn中模拟动态加载下脆性岩石渗透率变化，揭示裂纹扩展主导渗透率增强，并受连通性与闭合限制。
AI 中文摘要
我们提出了一种基于裂纹几何的模型，用于描述岩石在动态加载下的渗透率演化。准确表征渗透率对于地质构造中的流体提取和封存至关重要，但由于低孔隙度脆性岩石对孔隙几何和连通性的变化高度敏感，而动态渗透率测量又受到限制，因此这一任务仍具挑战性。岩石的孔隙空间被表示为具有规定取向的硬币形裂纹的演化网络。渗透率的变化通过裂纹微变量（包括开度、长度和裂纹间距）来描述。该模型考虑了裂纹的张开与闭合、断裂能驱动的扩展、塑性应变驱动的成核、完全连通后的合并，以及应变率相关的断裂增韧。演化的裂纹网络直接改变连通性、流体传导性和优先流动路径。该公式在GeoDyn流体动力学代码中实现，并在拉伸、剪切、压缩和对称冲击加载条件下进行了评估。结果表明，渗透率与裂纹长度之间存在强关联，裂纹扩展在渗透率增强中起主要作用。然而，渗透率的增长可能受到连通性差和裂纹闭合的限制。该模型捕捉了随应力状态、应变率、裂纹取向和连通性变化的多个数量级的渗透率变化，与高应变率加载下脆性岩石的观测行为一致。
英文摘要
We propose a crack-geometry-based model for permeability evolution in rocks under dynamic loading. Accurate representation of permeability is important for fluid extraction and containment in geological formations, but remains challenging because low-porosity brittle rocks are highly sensitive to changes in pore geometry and connectivity, while dynamic permeability measurements are limited. Rock void space is represented as an evolving network of penny-shaped cracks with prescribed orientations. Permeability changes are described through crack microvariables including aperture, length, and crack distance. The model accounts for crack opening and closure, fracture-energy-driven propagation, plastic-strain-driven nucleation, coalescence after full connectivity is reached, and strain-rate-dependent fracture toughening. The evolving crack network directly modifies connectivity, fluid conductance, and preferential flow paths. The formulation is implemented in the GeoDyn hydrocode and evaluated under tension, shear, compression, and symmetric impact loading. Results show a strong relation between permeability and crack length, with crack propagation playing a major role in permeability enhancement. Permeability growth can nevertheless be limited by poor connectivity and crack closure. The model captures changes of several orders of magnitude depending on stress state, strain rate, crack orientation, and connectivity, consistent with observed behavior of brittle rocks under high strain-rate loading.
Comments55 pages, 13 figures, includes a Supplementary Material
