Containment is considered the biggest risk in CCS operations because compromised cement sheath integrity can lead to CO2 leakage. The time duration specified for containment is decades. Conventional cements are unstable in CO2-rich environments and are subject to chemical attack by CO2 that slowly erodes the cement matrix. As a result, AGR’s primary objective was to achieve long-term zonal isolation across and above the CO2 storage zone for Australia’s first offshore CCS appraisal well and assure cement sheath integrity for the life of the well.
By leveraging the EverCRETE CO2-resistant cement system, AGR successfully provided long-term zonal isolation for the appraisal well in the CO2 environment. The operation was executed flawlessly without any lost time or HSE incidents, while ensuring adaptability of the well for future applications of CO2 injection. Not only was the solution more cost-effective compared with resin-based systems, but AGR also gained substantial savings due to the possibility of using the well for CCS in the future without risking costly remedial operations should containment fail due to use of conventional systems.
The project achieved several significant milestones, notably the first blending and on-the-fly mixing of the EverCRETE CO2-resistant cement system in Australia, along with the first offshore pumping of the EverCRETE system in the country. The blend is ideally suited and stable for use in Australia, where extensive transportation over both land and sea is typical. In this scenario, the blending facility was situated more than 900 km from the dock where the supply vessel would be loaded, and the mixture would need to be transported vertically approximately 50 m to reach the silos on the jackup rig. After enduring lengthy transportation, the blend was confirmed to be stable.
