Viscous and capillary forces competition triggered flow instability in porous media

作者：Jinxin Cao, Yiqiang Li, Yaqian Zhang, Xuechen Tang, Zheyu Liu, Qihang Li, Tao Song, Yuling Zhang · 发表于：Physics of Fluids · 年份：2025 · DOI：10.1063/5.0281257 · 被引用次数：9 · 研究领域：Enhanced Oil Recovery Techniques、Lattice Boltzmann Simulation Studies、Heat and Mass Transfer in Porous Media

The transport process of two-phase fluids in porous media significantly affects groundwater seepage and carbon capture, utilization, and storage, as well as oilfield development. Due to limitations in analytical methods, the dynamic mechanisms controlling pore-scale flow processes remain insufficiently understood. Based on image analysis technology, this research elucidates flow instabilities triggered by the competition between capillary and viscous forces and clarifies their underlying mechanisms. Displaced-phase microcapillary number is introduced to provide a comprehensive analysis of the two-phase flow behavior. The results indicate that as Camicro increases, crude oil recovery factor declines, and the displacement process transforms from stable to unstable, with a critical Camicro of 10−4.09. When Camicro = 10−4.33, viscous force dominates the flow process through Saffman–Taylor instability, exhibiting channeling with an extremely low recovery factor. When Camicro = 10−3.70, capillary force dominates the flow process. The rapid rebound of the local pressure causes a capillary burst, which makes the oil–water interface selection not follow the lowest threshold pressure rule. The sequential breakthrough effect, driven by the interaction between Saffman–Taylor instability and capillary burst, results in reduced residual oil in the swept area. As displacement progresses, the influence of viscous forces on oil–water distribution gradually weakens, while the impact of capilla...