Analysis of different oil well cement slurry formulations exposed to a CO2-rich environment

Portland cement hydrated products exposure to carbon dioxide (CO2) results in physicochemical transformations which are deleterious for the cement matrix. Therefore, cement slurry formulations need to be designed carefully to handle situations where the hardened cement will be exposed to CO2, so optimized formulations need to be considered. The present study investigated different cement slurry formulations and different densities for each formulation, with all samples exposed to CO2 during periods of 30, 60 and 90 days. The densities studied were 15.8 ppg (1890 kg/m3), 16.5 ppg (1980 kg/m3) and 17.0 ppg (2040 kg/m3), for which the study started with a simple composition and other additives were put into the formulations, with the last being the most complex. Static sedimentation analysis, carbonation depth and area calculation were used to investigate the effects of carbonation on the systems, and the results showed that the optimized formulation designs presented the best results on CO2 attack in the highest densities of 16.5 ppg and 17.0 ppg. A proper formulation designed for application in CO2-rich wells is mandatory for the well integrity from the construction phase to abandonment.