Case studies highlighted in the Offshore Energies UK Offshore Decommissioning Report 2024 have highlighted the importance of offshore engineering and preparatory work for safe and cost-effective outcomes in decommissioning projects.
OEUK cites AF Offshore Decom’s experiences with a bridge-linked flare stack, where extensive preparatory work, particularly from the platform complex, significantly reduced the time required for the heavy lift vessel (HLV) in the field. Additionally, by focusing the preparatory activities during the winter months, the team was able to optimise the use of the HLV for the summer, thereby enhancing operational efficiency.
In another case highlighted in the report, extensive preparatory works facilitated a smooth and effective removal of a major platform. Comprehensive helicopter surveys and a thorough engineering phase were undertaken, minimising unexpected issues during the main offshore removal campaign. This was followed by an HLV campaign when a crew handled the topsides preparations along with smaller modular lifts. A second HLV campaign included a large integrated modularised steel frame lift and an efficient jacket lift. The structures were then transported onwards to AF's environmental base to be dismantled and recycled onshore.
The phased execution helped to mitigate risk and allowed for detailed engineering and interface management, which was an important part of the project.
Optimising offshore operations for decommissioning projects in this way can make a substantial contribution to keeping costs down. This is critical in the Gulf of Mexico, where operators face spiralling decommissioning costs. Findings from a recent study published in Nature Energy showed that there are around 14,000 unplugged oil and gas wells in the Gulf of Mexico, with the process of plugging and decommissioning these wells estimated to cost around US$30bn.
