Enhancing CO₂ Sequestration in Saline Aquifer through Wettability Alteration: A Comprehensive Review of In-Situ Factors and Application of Nanofluid Technology

The injection of carbon dioxide into geological formations, referred to as geo-sequestration, emerges as a promising approach to mitigate environmental impact. However, the success of CO2 geo-sequestration projects hinges on the wettability of rock/CO2/brine. This study examines wettability alteration in sandstone and carbonate reservoir rocks and their representative proxy minerals, such as quartz, mica, calcite, and dolomite. In addition, the various in-situ influencing factors and current developments in wettability alteration utilizing nanofluid technology are thoroughly examined. This Review also highlights knowledge gaps and proposed directions for future studies. Despite conflicting reports, findings generally reveal that the contact angle, a commonly used test to determine wettability, increases with increasing pressure and salinity for sandstone and carbonate formations. On the contrary, temperature exhibits the opposite, and surface roughness appears to have a positive effect on sandstones and a negative effect on carbonates. Many laboratory and scientific studies have demonstrated that the injection of nanoparticles facilitates wettability alteration, which is particularly advantageous in CO2 geo-sequestration. In addition, considerable studies have shown that surfactants and nanoparticles working in tandem improved the stability and wettability modification even further. Nanotechnology has been shown to improve the wettability. However, its long-term effectiveness is severely affected by the aging process, which includes crystallization, solubilization, flocculation, and clustering of the nanoparticles. Future studies should investigate the impact of rock surface roughness on wettability and the importance of utilizing untreated natural rock samples to replicate reservoir conditions better. Lastly, nanoparticle stability/suspension and surfactant foam quality assessment in CO2 geo-sequestration systems remain inadequately investigated.