The capillary pressure curve is essential for predicting multiphase flow processes in geological systems. At low saturations, wetting films form and become important, but how wetting films control this curve remains inadequately understood. In this study, we combine microfluidic experiments with pore-network modeling to investigate the impact of corner-bridge flow on the capillary pressure curve in porous media. Using a CMOS camera and a confocal laser scanning microscopy, we directly observe the corner-bridge flow under quasi-static drainage displacement, revealing that corner-bridge flow serves as an additional flow path to drain trapped water. Consequently, the capillary pressure curve shifts toward lower saturations, resulting in a reduced water residual saturation. We establish a theoretical criterion for the occurrence of corner-bridge flow and develop a pore-network model to simulate quasi-static drainage, taking into account this additional flow path. Pore-network modeling results agree well with our experimental observation. On this basis, we employ our pore-network model to systematically analyze the impact of corner-bridge flow on capillary pressure curve across varying porosity, pore-scale disorder, and system size. Results indicate that the impact of corner-bridge flow becomes more pronounced as porosity decreases and shape factor increases. Our findings demonstrate that the maximum decrease of water residual saturation is 0.19 when porosity is at its minimum, and the shape factor is at its maximum. This work bridges the gap between the pore-scale mechanism and capillary pressure behavior and has significant implications for estimating the amount of extractable water and the CO₂ storage capacity.

中文翻译：

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角桥流对毛细管压力曲线的影响：来自微流体实验和孔隙网络建模的见解


毛细管压力曲线对于预测地质系统中的多相流过程至关重要。在低饱和度下，润湿膜会形成并变得很重要，但润湿膜如何控制这一曲线仍不清楚。在这项研究中，我们将微流体实验与孔隙网络建模相结合，以研究角桥流对多孔介质中毛细管压力曲线的影响。使用 CMOS 相机和共聚焦激光扫描显微镜，我们直接观察准静态排水位移下的角桥流，揭示了角桥流作为排出滞留水的额外流道。因此，毛细管压力曲线向较低的饱和度移动，导致水残余饱和度降低。我们建立了一个角桥流发生的理论标准，并开发了一个孔隙网络模型来模拟准静态排水，同时考虑到这个额外的流路。孔隙网络建模结果与我们的实验观察结果非常吻合。在此基础上，我们采用孔隙网络模型系统分析了角桥流对不同孔隙度、孔隙尺度无序和系统大小的毛细管压力曲线的影响。结果表明，随着孔隙率的降低和形状因子的增加，角桥流的影响变得更加明显。我们的研究结果表明，当孔隙度最小时，水残余饱和度的最大下降幅度为 0.19，而形状因子最大。这项工作弥合了孔隙尺度机制和毛细管压力行为之间的差距，对估计可提取水量和 CO₂ 封存能力具有重要意义。