Innovative Leaching Tests of an Oilwell Cement Paste for CO2 Storage: Effect of the Pressure at 80 °C

Old wells could be exposed to severe environment. This study reports the characterization of a class G oilwell cement paste exposed to a brine at high pressure and high temperature.The results showed that pressure had a strong impact on the phenomenology and the kinetics of oilwell cement paste degradation in selected downhole conditions. The alteration mechanism at high pressure appears to be more complex than the one observed at atmospheric pressure. At atmospheric pressure the diffusion rate governs the kinetics and thus is slower than the rate of the chemical reaction. On the other hand, it seems that an increase of pressure increases much more the diffusion rate than the rate of reaction. Future developments are proposed in order to improve the understanding of the long-term behavior of oilwell cement paste at downhole conditions.