Pore-scale simulation of three-phase displacement in 3D porous media using advanced LBM: insights into CO2 enhanced oil recovery and storage

Carbon dioxide enhanced oil recovery (CO 2 -EOR) is a promising technology that simultaneously increases oil production and facilitates CO 2 sequestration, addressing energy and environmental challenges. This study develops an advanced multiphase lattice Boltzmann model to simulate CO 2 -water–oil displacement in three-dimensional porous media, incorporating realistic fluid properties and dynamic interfacial behaviors. By systematically analyzing the effects of water saturation (S w ), wettability (θ), and capillary number (Ca), the study reveals critical insights into optimizing oil recovery and CO 2 storage efficiency. Results demonstrate that at lower water saturation (S w = 0.4), enhanced oil phase connectivity leads to maximum oil recovery efficiency of 33.5 %, while higher water saturation (S w = 0.8) facilitates CO 2 storage, achieving a storage efficiency of 64.1 %. Wettability exhibits a dual regulatory effect: water-wet conditions maximize oil recovery, whereas oil-wet conditions enhance CO 2 storage efficiency. Furthermore, increasing the Ca from −3.2 to −2.2 significantly improves oil recovery and CO 2 storage efficiency, highlighting the importance of viscous forces in overcoming capillary barriers. The study introduces a novel Ca-θ-S o /S g color diagram, allowing precise quantification of oil recovery and CO 2 storage efficiencies across varying wettability and Ca conditions. A binomial empirical formula for the color diagram enables rapid estimation of efficiencies, with R 2 values exceeding 0.92. Notably, the nonlinear relationship between oil recovery and CO 2 storage efficiency underscores the complex interplay of multiphase flow mechanisms. This work provides a robust theoretical framework and practical tools for reservoir engineering, offering actionable strategies for optimizing CO 2 injection schemes and enhancing geological CO 2 storage. These findings advance the understanding of multiphase displacement dynamics and establish a foundation for the further development of CO 2 -EOR and storage technologies.