DeepOcean Completes Major Decommissioning Project in the North Sea

Normand Jarstein. Credit: DeepOcean

Ocean services provider DeepOcean has successfully completed a significant subsea decommissioning project for a client in the central North Sea, reaching a 98 percent recycling rate for the removed subsea infrastructure.

DeepOcean undertook an ambitious scope of work encompassing the removal of three significant fields, executing over 300 LTI free vessel days during a six-month offshore campaign. The project involved the recovery of almost 9000 tonnes of subsea infrastructure, with 98 percent recycled or re-used through DeepOcean’s key waste management provider for the project.

Key highlights of the campaign included flexible riser and umbilical recovery; mid-water arch release and tow; removal of a nine-leg FPSO mooring system; recovery of various piled and non-piled structures including production manifolds and a subsea safety isolation valve module; concrete mattresses, general debris recovery and subsea rock installation.

The campaign was project managed and engineered from DeepOcean’s Aberdeen office, with further support from the company’s Haugesund and Stavanger offices in Norway.

Although multiple vessels within DeepOcean’s fleet were used, the majority of the workscope was completed by the Normand Jarstein and the hybrid battery-powered vessel, Edda Freya. This work included the recovery of over 700 concrete mattresses to the Normand Jarstein, using the UTROV mattress recovery system, with no dropped objects.

For the removal of the FPSO mooring system, DeepOcean performed the pump-out and recovery of three 7-metre diameter suction anchors, weighing approximately 110 tonnes, onto the Edda Freya. Over 3 kilometers of studless mooring chain and 7.7 kilometers of spiral strand wire were also recovered. DeepOcean also conducted the external dredge and cut of the remaining six 5-metresuction anchors at a depth of 3 meters below seabed.

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