Experimental Study of Wellbore Integrity for CO₂ Geological Storage

Storing CO₂ into a suitable underground geological formation is considered the most effective way for a safe and definitive CO₂ sequestration. Depleted hydrocarbon reservoirs are potential sites for injection and permanent CO₂ storage. The wells drilled which have been duly plugged and abandoned constitute one of the main risks directly affecting permanent and safe CO₂ storage, due to possible material deterioration around the wellbore, including the durability of the cement. Therefore, deep abandoned wells represent the greatest risk for potential leakage pathways along the wellbore's structure. Accordingly, a new experimental procedure is proposed here to improve our understanding of reactivity of CO₂-brine-well cement systems. For the experimental tests, API Class G cement samples were prepared by following the same industrial cementing process conditions used in the depleted Goldeneye gas condensate reservoir (North Sea). The analysis further shows variations of permeability with confining pressure and depth. The permeability increases with depth, from 2.06 x 10^-21 m² (at 1296 m depth) to 1.17 x 10^-20 m² (at 2560 m depth).