Residual water formation during the CO2 storage process in deep saline aquifers and factors influencing it: A review

There are number of influencing factors on the residual water formation process, which are mainly related to the physical properties of the reservoir and the injected CO2 properties and process. These factors include, CO2-brine interfacial tension (IFT)-related factors, contact angles in brine-CO2-rock systems, aquifer rock mass heterogeneity and mineral composition, the permeability and porosity of the aquifer, two-phase equilibrium, and CO2 injection rate and duration. However, it should be noted that these factors mutually contribute to residual water formation in saline aquifers during CO2 sequestration and therefore, the overall influence decides the efficiency of the final residual water formation in the aquifer. This work is a state-of-the-art report on the effectiveness and evaluation of reservoirs for CO2 storage purposes.