Investigation of gravity in fl uence on EOR and CO 2 geological storage based on pore-scale simulation

Gravity assistance is a critical factor influencing CO 2 -oil mixing and miscible flow during EOR and CO 2 geological storage. Based on the Navier-Stokes equation, component mass conservation equation, and fluid property-composition relationship, a mathematical model for pore-scale CO 2 injection in oilsaturated porous media was developed in this study. The model can reflect the effects of gravity assistance, component diffusion, fluid density variation, and velocity change on EOR and CO 2 storage. For nonhomogeneous porous media, the gravity influence and large density difference help to minimize the velocity difference between the main flow path and the surrounding area, thus improving the oil recovery and CO 2 storage. Large CO 2 injection angles and oil-CO 2 density differences can increase the oil recovery by 22.6% and 4.2%, respectively, and increase CO 2 storage by 37.9% and 4.7%, respectively. Component diffusion facilitates the transportation of the oil components from the low-velocity region to the main flow path, thereby reducing the oil/CO 2 concentration difference within the porous media. Component diffusion can increase oil recovery and CO 2 storage by 5.7% and 6.9%, respectively. In addition, combined with the component diffusion, a low CO 2 injection rate creates a more uniform spatial distribution of the oil/CO 2 component, resulting in increases of 9.5% oil recovery and 15.7% CO 2 storage, respectively. This study provides theoretical support for improving the geological CO 2 storage and EOR processes. (c) 2023 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).