Abstract
The injection of CO(2) into shale gas reservoirs can not only enhance shale gas recovery (ESGR), but also realize CO(2) geological storage (CGS). In this study, the competitive adsorption behaviors of CO(2) and CH(4) in shale were systematically reviewed, and the implication for shale gas recovery efficiency and CO(2) storage potential were discussed. The adsorption advantage of shale for CO(2) compared to CH(4) provides a guarantee of the feasibility of supercritical CO(2) (ScCO(2)) enhanced shale gas exploitation technology. The selective adsorption coefficient of CO(2) and CH(4) by shale (S (CO(2)/CH(4)) ) is an important parameter in evaluating the competitive adsorption behavior of CO(2)/CH(4) in shale gas reservoirs, which is closely related to the mineral composition, reservoir temperature, pressure conditions, water content, and mixed gas composition ratio. In addition, the injection type, injection mode, and injection rate of gases also exhibit different effects on CO(2)/CH(4) competitive adsorption. Furthermore, the interaction between ScCO(2) and the water-rock system will change the mineral composition and microstructure of shale, which will lead to changes in the adsorption behavior of shale on CO(2) and CH(4), so its influence on the competitive adsorption of CO(2)/CH(4) cannot be ignored. Future research should integrate different research methods and combine with practical engineering to reveal the competitive adsorption mechanism of CO(2)/CH(4) in shale reservoirs from both micro and macro aspects. This study can provide support for the integration technology of ScCO(2) enhanced shale gas exploitation and its geological storage.