Abstract In the context of CO2 geological storage, storage capacity and safety are two aspects to be evaluated in order to ensure the efficiency of this operation. The safety of this technique is primarily related to the conservation of the intrinsic properties of the caprock (stratigraphic trapping), which are controlled by the porous structure. This paper focuses on the assessment of the impact caused by the CO2/water interaction on the porous nanostructure. A suspension of crushed rock samples and synthetic water was reacted with supercritical CO2 at 84 bar and 53 ̊C under static conditions over a 2-month period. At the end of the experiment, the solid and liquid phases were collected in order to analyze the porous structure of the rock and water chemistry. Over short time periods, the results show a slight increase of the microporous and mesoporous volumes due to the rapid dissolution of calcite compared to the slower dissolution of aluminosilicates.