Hypothesis: Nanofluid treatment is a promising technique which can be used for wettability reversal of CO2-brine-mineral systems towards a further favourable less CO2-wet state in the existence of organic acids. However, literature requires more information and study with respect to organic acids and nanoparticles' effect at reservoir (high pressure and high temperature) conditions. Experiments: Therefore, we have measured in this study that what influence small amounts of organic acids exposed to quartz for aging time of (7 days and 1 year) have on their wettability and how this impact can be reduced by using different concentrations of nanoparticles at reservoir conditions. Precisely, we have tested lignoceric acid (C-24), stearic acid (C-18), lauric acid (C-12) and hexanoic acid (C-6) at 10(-2) Molarity, as well as, we have also used different concentrations (0.75 wt%, 0.25 wt%, 0.1 wt%, 0.05 wt%) of silica nanoparticles at realistic storage conditions. Findings: The quartz surface turned significantly hydrophobic when exposed to organic acids for longer aging time of 1 year, and significantly hydrophilic after nanofluid treatment at optimum concentration of 0.1 wt%. It was observed that most nanoparticles were mechanistically irreversibly adsorbed on the surface of quartz sample. This wettability shift thus may increase CO2 storage capacities and containment security. (C) 2019 Elsevier Inc. All rights reserved.