Evolution of resistivity and permeability of wellbore cement after corrosion by supercritical CO2 in geological CO2 storage conditions

It is important to understand and monitor wellbore potential damage for the safety of the geological CO2 storage project. The leaked CO2 is susceptible to a chemical reaction with the alkaline cement that can damage the sealing effect of the wellbore structure. In this study, a test of cement corrosion by supercritical CO2 was designed and the evolution of damaged cement resistivity and permeability were tested. The results of the study are as follows:(1) In the case of cement immersed in brine and placed in supercritical CO2, its resistivity exhibited a linear decrease with corrosion time, whereas permeability increased linearly with corrosion time. These are the result of a gradual increase in the porosity of the cement corroded by CO2. (2) In the case of cement that is directly exposed to supercritical COQ, its resistivity exhibited a linear increase with corrosion time, whereas permeability decreased linearly with corrosion time. The gradual decrease in porosity of the cement, caused by the corrosion of CO2, contributes to these alterations. (3) A chemical reaction process analysis reveals that the discrepancy between the two cement corrosion characteristics mentioned above lies in whether the carbonation product CaCO3 can continue to be dissolved in the reaction system.