Closed wellbore integrity failure induced by casing corrosion based on solid-chemical coupling model in CO2 sequestration

The safety and stability of carbon sequestration are key in CCS technology, and the wellbore is a critical pathway for leakage, which can lead to the failure of sequestration. In this study, the process of casing corrosion-induced closed wellbore integrity failure is investigated based on a solid-chemical coupling model. The influence of temperature and CO2 pressure on the development of cement damage is also investigated. The results show that the corrosion rate increases and then decreases with increasing depth, and the time of damage initiation gradually shifts backward. During the process of casing corrosion-induced cement damage, the corrosion scale that accumulates on the surface of the casing causes stress redistribution within the cement system. The damage initiates at the interface between the bottom of the cement system and the casing, progressing upwards to create a potential leakage pathway. Moreover, the damage in the cement sheath develops more rapidly, while the rate of damage development in the cement plug gradually decreases. This study will be helpful for understanding the initial stage of closed wellbore failure in carbon sequestration and for implementing corresponding preventive measures in engineering practice.