The Sonsub Division of Saipem UK has recently completed the offshore campaign for the Total Frigg Sealines Cessation Plan, resulting in a successful conclusion to the project.
The Frigg field straddles the boundary between the Norwegian and UK Continental Shelves in the North Sea, with the project involving the decommissioning of all sealines within a designated 500m zone.
The Sonsub scope of work comprised the engineering, preparation, removal and disposal of all infield sealines, plus all power cables, umbilicals, communication lines, grout bags, sand bags and concrete mattresses, saddles and blocks. Additional scope included rock berm smoothing and general debris clearance.
Following the Normand Cutter offshore campaign, the multipurpose offshore support vessel Far Sovereign completed the recovery of all the infield flexible and small diameter rigid lines utilising a reverse reeling method - a first time for Sonsub. A further milestone achievement for the company was the recovery of four rigid and flexible lines from beneath a large rock dump without the need for complete prior excavation.
All operations were carried out in a safe and efficient manner. Sonsub will continue decommissioning work on the Frigg DP1 platform later this year.
Sonsub assets and operations manager John Ewen commented: "As with all decommissioning projects, Frigg Sealines proved to be a real challenge requiring innovation during the engineering phase and a capacity to address unforeseen problems throughout offshore execution. The bespoke design and build of decommissioning tools developed for the project leaves Sonsub Division well placed to tackle future projects involving the removal of rigid pipelines and flexible products."