With the Viking Vulcan offshore gas production assets reaching the end of their effective life, ConocoPhillips decided to decommission them in their entirety. A significant amount of preparatory work needed to be completed before a heavy lift vessel arrived on location to remove the topsides and jackets.
The client chose to bring the assets to a state of readiness where they could be left in lighthouse mode until a heavy lift vessel could be sourced, after which the structures would be removed for recycling or disposal. The work was carried out in challenging offshore conditions across multiple phases.
DSL was awarded two work packages: one by ConocoPhillips as operator and one by Royal Boskalis Westminster as heavy lift contractor. Working for both parties created a one team approach, with multi-disciplined personnel on the asset and open sharing of information between client, construction contractor and heavy lift contractor.
For the operator, our team provided onshore project management, engineering and fabrication, and rope access welders, platers, pipefitters, riggers and E&I technicians to remove redundant equipment, install lifting points, remove caissons, risers and J-tubes, clear sling paths, air gap the structures, install leg cutting platforms and remove the communications tower. The contract completed in July 2017.
For Boskalis, DSL provided decommissioning support services, including all above water leg cutting, throughout the 2019 multi-phase Southern North Sea campaign. This covered spider deck access, cutting penetrations for rigging, fairlead bollards and trunnion lift points, topside separation cuts at El +17.3, external pile cutting, removal of leg extensions at El +7.9, rigging and steering wire installation and sea fastening of the topsides and jackets.
Seven jackets and four topsides were successfully removed from the field and transported ashore for dismantling. Robust planning, comprehensive pre-works and the one team philosophy were significant contributors to successful execution, and open discussion between the parties led to cost and time efficiencies.
DSL completed more than 90,000 man-hours without incident on the operator package, including over 7,000 hours on rope, and more than 38,000 rope access and non rope access man-hours without a lost time incident during the 2019 campaign.
