Cement additives to mitigate wellbore cement degradation in CO2 corrosive environment: A review

Abstract

To mitigate climate change concerns and fulfil the net-zero emission targets, CO₂ geological utilization and storage (CGUS) is currently the most promising strategy for reducing anthropogenic CO₂ emission levels. CGUS involves injecting captured CO₂ into deep geological formations. Wellbore cement, as an integral part of the CGUS system, is chemically unstable in CO₂-rich conditions because exposure of its hydrated products to CO₂ causes physicochemical changes that are harmful to the cement matrix. Exposure to CO₂ results in cement degradation and integrity loss, which is a major cause of CO₂ leakage via wellbores. Therefore, to minimize cement integrity loss, cement slurry must be properly prepared. Researchers have made notable advancements in formulating cement by incorporating diverse additives into cement to boost its resistance to CO₂ corrosion. This review intends to summarize the findings from recent advances of CO₂ corrosion remediation using various cement additives, as well as to highlight their potential to be incorporated into wellbore cement to mitigate CO₂ corrosion. Furthermore, the key mechanisms by which different additives enhance the effectiveness of CO₂ corrosion mitigation have been demonstrated. In light of current research advances and existing problems, gaps in the research have been identified and considerations for future development of formulations of CO₂-resisting wellbore cement slurry have been provided.