Pore-scale study of drainage behavior in gradient porous media
Zhou Y. Zhang Y. Zhussupbekov A. Zhang C. Guan W.
1 February 2026American Institute of Physics
Physics of Fluids
2026#38Issue 2
Gradient porous media, characterized by continuously varying pore sizes along the flow direction, fundamentally reorganize the interplay between viscous and capillary forces. Yet, how such geometric gradients modulate pore-scale drainage dynamics and displacement efficiency remains insufficiently understood. In this study, we employ the lattice Boltzmann method to investigate immiscible drainage in a three-dimensional granular packing exhibiting a clear pore-size gradient. By imposing two opposite injection directions within the same structure—corresponding to gradually increasing or decreasing pore sizes—we systematically examine how geometric gradients influence fingering behavior, interface morphology, pressure evolution, and breakthrough efficiency across a broad range of capillary numbers and viscosity ratios. Our results show that increasing pore sizes along the flow direction promotes both viscous and capillary fingering, enabling early breakthrough but reducing displacement efficiency except under stable displacement. In contrast, decreasing pore sizes suppress fingering, enhance lateral invasion, and allow high efficiency even within the capillary fingering regime. Dynamic pressure analyses further reveal that gradient-induced variations in local capillary resistance and pore-scale velocities govern the stability of the displacement front. These mechanisms collectively lead to markedly different phase diagrams for the two flow directions. Overall, the findings demonstrate that the direction of flow relative to a pore-size gradient constitutes a previously underappreciated yet powerful control parameter for optimizing immiscible displacement in heterogeneous porous formations.
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Department of Astronautics and Mechanics, Harbin Institute of Technology, Harbin, 150090, China
Department of Civil Engineering, L.N. Gumilyov Eurasian National University, Astana, 010008, Kazakhstan
Zhengzhou Research Institute, HIT, Zhengzhou, 450000, China
Department of Astronautics and Mechanics
Department of Civil Engineering
Zhengzhou Research Institute
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026