Abstract A series of fracture geometries of an artificially tensile fractured sandstone, measured during the hydraulic tests at increasing confine stresses, were adopted to build 3D fracture models. At each stress level, four groups of flow simulations with increasing injection flow rates were conducted, to examine how voids and contact alterations due to stress changes affect the flow characteristics within the fracture. The results show that the simulated normalized apparent transmissivity matched well with that measured from hydraulic tests, and both them decreases nonlinearly with increasing confine stress. The alterations in fracture geometries due to stress changes increase the heterogeneities of flow characteristics in 3D fractures, including flow rates, streamlines, water pressure. The streamlines become more channeled with observable tortuosity under high stress. The stress induced increase in contact and the occurrence of eddy flow enhance the non-linearity of pressure drop. The decrease of both apertures and sharp geometries under high stress reduces the range of eddy flows, which delays the occurrence of significant inertial effects and results in the increase of critical Reynolds numbers. These features are demonstrated well using an idealized 3D representative geometric including both the asperity contacts and voids.

中文翻译：

---

约束应力下几何变化的 3D 粗糙岩石裂缝流动特性建模

摘要 采用一系列人工拉伸裂缝砂岩的裂缝几何形状，在增加的限制应力下进行水力试验期间测量，用于建立 3D 裂缝模型。在每个应力水平，随着注入流速的增加，进行了四组流动模拟，以检查由于应力变化引起的空隙和接触变化如何影响裂缝内的流动特性。结果表明，模拟的归一化视透射率与水力试验测得的透射率匹配良好，且均随着围压的增加呈非线性下降。由于应力变化引起的裂缝几何形状的变化增加了 3D 裂缝中流动特性的异质性，包括流速、流线、水压。在高应力下，流线变得更加通畅，具有可观察到的曲折。应力引起的接触增加和涡流的出现增强了压降的非线性。在高应力下孔径和锐利几何形状的减少减小了涡流的范围，从而延迟了显着惯性效应的发生并导致了临界雷诺数的增加。使用理想化的 3D 代表性几何图形（包括粗糙接触和空隙）可以很好地证明这些特征。这延迟了显着惯性效应的发生并导致临界雷诺数的增加。使用理想化的 3D 代表性几何图形（包括粗糙接触和空隙）可以很好地证明这些特征。这延迟了显着惯性效应的发生并导致临界雷诺数的增加。使用理想化的 3D 代表性几何图形（包括粗糙接触和空隙）可以很好地证明这些特征。