Density-Driven Convection for CO2 Solubility Trapping in Saline Aquifers: Modeling and Influencing Factors

Industrial development has significantly increased the concentration of CO2 in the atmosphere, resulting in the greenhouse effect that harms the global climate and human health. CO2 sequestration in saline aquifers is considered to be one of the efficient ways to eliminate atmospheric CO2 levels. As an important mechanism, the solubility trapping greatly determines the efficiency of CO2 sequestration in saline aquifers, and this depends, in turn, on the density-driven convection that occurs during the sequestration. Density-driven convection is influenced by multiple factors. However, existing discussions on some of these influential factors are still ambiguous or even reach contradictory conclusions. This review summarizes the common modeling approaches and the influence of factors on density-driven convection. We suggest that saline aquifers with high values of depth, permeability, pH, and SO2 impurity concentration are the ideal CO2 sequestration sites. A certain degree of porosity, fractures, stratification, slope, hydrodynamic dispersion, background flow, and formation pressure are also considered advantageous. Meanwhile, the geological formation of the Permian White Rim Sandstone or carbonate is important, but it should not contain brine with excessive viscosity and salinity. Finally, we discuss the contents in need of further research.