Review of CO2 sequestration mechanism in saline aquifers

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The concentration of CO2 in the global atmosphere, which is increasingly annually with continued industrial development, affects both the global climate and the ecological environment. To control the concentration of atmospheric CO2, various methods of carbon capture and sequestration have been proposed and continue to be developed. Among them, CO2 sequestration in saline aquifers has potential for effective high-capacity carbon storage. This work reviews both the research status of structural, residual, solubility, and mineral CO2 sequestration in saline aquifers, and the research progress associated with the integrity of cement sheaths and caprocks. The findings indicate that structural sequestration research must comprehensively consider the influence of various factors, and that the capacity of structural sequestration must be evaluated based on the actual geological conditions of the saline aquifer, caprock properties, and CO2 injection rate. The heterogeneity of the caprock and dynamic changes of CO2 concentration are not considered in current simulations of the effect of chemical interaction between CO2-rich brine and the caprock. Residual sequestration and solubility sequestration are mutually interactive; therefore, exploration of the residual sequestration mechanism must consider the impact of solubility sequestration. Models for simulation of CO2 solubility sequestration in an entire saline aquifer should be developed to reservoir scale and must consider reservoir heterogeneity.