Volume 66

Implications for EOR and CO₂ Sequestration: Competitive Adsorption in Water-Containing Kerogen Shanshan Yang, Zhengfu Ning, Ying Kang

Abstract

The competitive adsorption between shale oil and CO₂ in water-containing kerogen is of great significance for CO₂ enhanced oil recovery (CO2-EOR) and CO₂ sequestration. In this study, molecular dynamics (MD) method was used to construct dry kerogen model, and grand canonical Monte Carlo (GCMC) method was used to construct shale reservoir kerogen model with different water contents. By combining the GCMC and MD methods, the competitive adsorption behavior of shale oil and CO₂ in water-containing kerogen was simulated. The adsorption characteristics and kinetic phenomena of different adsorbates were discussed, and the feasibility of CO₂ sequestration was evaluated. The results show that as the water content increases, the CO₂ adsorption capacity decreases, while the isosteric heat of adsorption remains initially lower and then rises. In multi-component systems, as the water content increases, the adsorption capacity of shale oil weakens, and the displacement effect of CO₂ on shale oil improves. The adsorption capacity of long-chain alkanes in shale oil is relatively weak, and the competitive adsorption between short-chain alkanes and CO₂ becomes more obvious. Importantly, regulated by water content, the adsorption selectivity of CO₂ is conducive to its sequestration under the condition of appropriate water content. Meanwhile, water-alternating-gas (WAG) injection can be considered as an effective method for EOR. This study quantitatively reveals the competitive adsorption characteristics of shale oil and CO₂ in water-containing kerogen, and offers insights at the microscopic scale for the efficient and green development of shale oil reservoirs.

Keywords Competitive adsorption, Kerogen, Water content, Shale oil, Carbon dioxide, Molecular simulation