Unlocking the potential of CO2 storage in saline aquifers: Challenges, knowledge gaps, and future directions for large-scale storage

Saline aquifers represent a significant geological option for large-scale CO2 storage through CO2 solubilization in brine and subsequent geochemical interactions that facilitate mineralization. Nevertheless, their heterogeneous nature influences the kinetics of CO2 dissolution and long-term stability. This review assesses advancements in experimental and modelling efforts regarding CO2 solubilization in saline aquifers, considering natural convection, diffusion, and dispersion factors. It also investigates the application of nanobubble technology to enhance storage capacity and stability, along with various technologies that could be utilized for its generation. Furthermore, geochemical implications, mineral trapping, and field-scale observations have been reviewed to offer a comprehensive understanding of the storage mechanisms. Our findings indicate that optimizing brine chemistry and harnessing nanobubble technology could augment storage capacity and security. Furthermore, careful selection of injection sites, CO2 injectivity, and the security of injected CO2 are factors that must be addressed to unlock the storage potential of saline aquifers. Moreover, enhanced modelling approaches are required to reflect aquifer heterogeneity, which continues to pose a significant challenge in accurately modelling the long-term behaviour of CO2 in saline aquifers.