Wellbore integrity and corrosion of carbon steel in CO2 geologic storage environments: A literature review

Depleted oil and gas fields are attractive candidates for carbon capture and storage (CCS). As it contemplates the transition from CO2 enhanced oil recovery (EOR) to CCS, the Weyburn–Midale CO2 project is one such site. In the long-term risk assessment for Weyburn–Midale, wellbore integrity was identified as being a significant risk factor with respect to the permanence of CO2 sequestration. In an optimal situation, cementing will be good for both completion and abandonment; contact of CO2 with casing will be governed by cement permeability and interface effects. However, in the event of there being a poorly cemented casing-hole annular space, a more direct contact between the now “wet” injected CO2 and the casing steel will be possible. Consequently, this will lead to corrosion of the steel and the potential for CO2 leakage. The corrosion rate of carbon steel under high CO2 pressure without protective FeCO3 is very high (∼20 mm/year). At certain conditions, the corrosion rate can decrease to low values (∼0.2 mm/year) in long-term exposure due to the formation of a protective layer of FeCO3.

► The effect of the quality of cement jobs on corrosion of casing steel was reviewed and discussed.
► Possible pathways in cement that permit corrosive fluid to attack casing were reviewed and discussed.
► Corrosion behavior of carbon steel under CO2 geologic storage conditions was reviewed and discussed.