Publications Details

Precipitation/dissolution of calcium carbonate in wellbore cement and its implications for the seal integrity of abandoned wells

Matteo, Edward N.; Huet, Bruno; Scherer, George W.

Wellbore integrity of abandoned wells is of high priority for ensuring the containment of sequestered CO₂. Carbonic acid formed when injected CO₂ mixes with subsurface brines has the potential to damage well cement so as to compromise the seal integrity of the wellbore. Bench-scale experiments reported in the literature indicate that the well cement reaction rates are initially fast enough to constitute a potential threat to wellbore integrity. However, it has also been suggested that the formation of calcium carbonate within the cement effectively arrests the acid attack by forming a passivation layer (so called “self -sealing”) that prevents further leaching of cement minerals. As a result, a broader theoretical context is presented here that delineates brine composition regimes that will instigate self-sealing in cement during carbonic acid attack.