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 (similar to 20 mm/year). At certain conditions, the corrosion rate can decrease to low values (similar to 0.2 mm/year) in long-term exposure due to the formation of a protective layer of FeCO3. (C) 2013 Elsevier Ltd. All rights reserved.