Multi-scale studies of oil–water imbibition mechanism on complex pore structures and mixed-wettability: a recent 10-year review

In the development of low-permeability reservoirs, imbibition oil recovery technology is recognized as one of the effective means to enhance oil recovery. A thorough understanding of the influence of pore structure and wettability on oil-water imbibition mechanisms is critical. This review summarizes experimental studies, theoretical models, and numerical simulations related to oil-water imbibition over the past decade. For example, the reconstruction of digital rock cores using advanced imaging techniques such as X-ray computed tomography (CT) to statically visualize and characterize the microscopic mechanisms of oil-water migration; the application of mathematical methods, including the Young–Laplace law, Hagen−Poiseuille equation, and fractal theory to describe oil-water transport characteristics within pores; and the use of numerical approaches, such as the pore network (PN) model, lattice Boltzmann method (LBM), and phase-field theory to analyze the influence of various factors on imbibition recovery efficiency at mesoscopic and macroscopic scales. Furthermore, this study provides an in-depth discussion on the complex effects of pore structure and wettability on the oil-water imbibition process across different scales. Finally, future research hotspots are proposed: (1) Achieving accurate characterization of complex pore structures and complex mixed-wettability in physical and three-dimensional numerical models across multiple scales; (2) Developing an integrated displacement-real-time CT scanning clamping device to achieve 4D visualization and quantitative description of oil-water migration flow behavior in complex pore structures; (3) Integration of AI with advanced algorithms to develop novel microfluidic chips enabling intelligent control of complex pore structures and complex mixed-wettability; (4) Elucidation of the cross-scale relationships of oil-water migration and implementation of scale upgrade methodologies linking microscale mechanisms, mesoscopic influencing factors, and macroscopic imbibition recovery effect. This study highlights the impact of pore structure and wettability on oil-water imbibition mechanism and provides an outlook on future research directions in the field, with the aim of advancing safe, efficient, and low-carbon development of low-permeability reservoirs.