Theory and Mechanisms of Carbon Dioxide Geological Storage

The theoretical framework and mechanistic system of CO2 geological storage constitute the core scientific foundation for understanding the essence of the storage process and guiding engineering practice. This section begins with an analysis of the fundamental conditions, providing a detailed exposition of the physicochemical properties of CO2, the characteristics of storage media, and the geological compatibility requirements, thereby offering material and environmental bases for feasibility assessment. It then delves into the core theoretical models, including fluid substitution theory (incorporating the Gassmann equation and the variation patterns of reservoir elastic parameters) and multiphase-multifield coupling theory (covering seepage, convective dispersion, rock deformation, temperature fields, and their interrelations), establishing quantitative analytical and predictive tools for the storage process. Finally, it focuses on typical scenario mechanisms, elucidating the intrinsic mechanisms of CO2-enhanced oil recovery (EOR), enhanced coalbed methane recovery (ECBM), and saline aquifer storage. The content of this section not only consolidates the theoretical foundation of CO2 geological storage, but also provides key scientific support for engineering scheme design, optimisation of storage effectiveness, and long-term safety assessment, serving as a crucial link between fundamental research and practical application.