CO2 enhanced shale oil and carbon sequestration in kerogen nanopores: A molecular dynamics study

Abstract

Carbon dioxide (CO₂) injection is a promising strategy for enhancing shale oil recovery while enabling geological carbon storage. In this study, non-equilibrium molecular dynamics (NEMD) simulations were employed to investigate CO₂-driven shale oil transport in kerogen nanopores with complex surface characteristics. The distribution and migration behaviors of multiphase shale oil were analyzed, and the effects of pore size, temperature, and injection pressure on fluid flow and CO₂ sequestration were systematically evaluated. The results show that shale oil forms three distinct adsorption layers within kerogen nanopores, with the first layer exhibiting a peak density of approximately 1.13 g/cm³, which is about 1.85 times higher than that in the free region. The irregular kerogen surface increases the resistance to shale oil desorption, resulting in slower CO₂-driven displacement compared with smooth graphene pores. Increasing pore size, temperature, and injection pressure significantly promotes shale oil desorption and enhances CO₂ storage capacity. For example, when the pore size increases from 2 nm to 5 nm, the shale oil adsorption fraction decreases markedly while CO₂ storage increases significantly. Temperature also plays an important role in regulating adsorption and sequestration behavior. Overall, this study reveals the molecular-scale mechanisms governing CO₂-enhanced shale oil mobilization and carbon sequestration in kerogen nanopores, providing theoretical insights for optimizing CO₂ injection strategies in shale reservoirs.