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

• Main Authors: Matteo, Edward N., Huet, Bruno, Scherer, George W.
• Language: unknown
• Published: 2021
• Subjects: 58 GEOSCIENCES; Carbonic acid
• Online Access: http://www.osti.gov/servlets/purl/1326359; https://www.osti.gov/biblio/1326359

Wellbore integrity of abandoned wells is of high priority for ensuring the containment of sequestered CO 2 . Carbonic acid formed when injected CO 2 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.