The presence of rock heterogeneity and fractures may cause abrupt spatial changes in capillary action and flow characteristics, which eventually change the precipitation behavior during CO₂ geological storage. Therefore, the salt precipitation mechanism of the heterogeneous structure needs to be studied. In this paper, the salt precipitation behavior in different heterogeneous structures was studied through pore-scale experiments at room temperature and atmospheric conditions. In the up-down heterogeneous structure, the salt precipitation has little effect on the injectivity regardless of the CO₂ injection rate. When the CO₂ injection rate is low, the salt tends to precipitate in situ in the small pore structure to form a crystal structure. When the CO₂ injection rate is high, the salt tends to precipitate in the large pore structure to form a cluster structure. In the left-right heterogeneous structure, regardless of the CO₂ injection rate, the precipitated salt is mainly in the cluster structure, and the salt is more dispersed in distribution, the impact on injectivity is small. The injection well can be selected in the formation with strong heterogeneity, to alleviate the blockage caused by salt precipitation. When CO₂ leaks in the fractures, salt tends to grow until the fracture is plugged, which is of great significance for the self-healing of the fracture for the caprock.

Carbon capture, utilization and storage (CCUS) refers to the separation of CO₂ from energy utilization systems, industrial production or the atmosphere followed by purification and transport to facilities using CO₂ or to storage sites to achieve long-term separation of the CO₂ from the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) recently stated that CCUS systems are a "foundation" technology for carbon emission reduction and carbon neutrality. CCUS technologies are indispensable key technologies in China's "two-carbon" goal for a carbon neutral China. This paper reviews the key heat and mass transfer issues for carbon dioxide geological storage, CO₂ enhanced tight oil/shale gas/deep geothermal energy recovery in recent years by major international and domestic research groups including the authors' research group. These studies have used theoretical analyses, simulation methods including molecular dynamics, lattice Boltzmann, and computational fluid dynamics, as well as experimental methods including pore-scale visualization experiments, core-scale nuclear magnetic resonance investigations, and supercritical pressure fluid convection heat transfer investigations. These studies have analyzed the multiphase, multicomponent flow and heat and mass transfer mechanisms of supercritical CO₂ in micro-nano porous structures for reservoir conditions at various scales. The influences of mineral reaction, CO₂ exsolution, fluid physical properties, and scale effects on the CO₂ geological storage, oil displacement, gas displacement, and heat recovery have been analyzed to provide theoretical and technical support for CO₂ geological storage and utilization.