CO2-wettability reversal of cap-rock by alumina nanofluid: Implications for CO2 geo-storage

The usage of nanofluids is vast in different applications of nano-energy. These minute nanoparticles can be used to alter the hydrophobicity into hydrophilicity for CO2-brine-mineral systems in the presence of organic acids. Nonetheless, the literature lacks the information for the behavior of nanoparticles and its associated concentrations in the presence of organic acids at the reservoir (high temperature and high pressure) conditions. In this study, we have investigated that how different alkyl chain organic acids impact the wettability of mica muscovite for different ageing times (7 days and one year) and how this impact can be reversed by nanofluid priming at different concentrations. To do that, we have used different organic acids with different alkyl chain lengths (hexanoic acid C6, lauric acid C12, stearic acid C18, and lignoceric acid C24) at 10−2 mol/L. We have also used different Al2O3 nanoparticle suspensions (0.05 wt%, 0.1 wt%, 0.25 wt% and 0.75 wt%) in deionized water. When mica substrates were exposed to organic acids for a longer ageing time of 1 year, it has lost its water-wetness rapidly at maximum. Whereas this effect was optimally reduced by 0.25 wt% of alumina nano-formulation and mechanical irreversible adsorption of alumina nanoparticles was noted on mica substrates. This reversal of wettability may raise the containment security and CO2 structural trapping potential.