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DOF Subsea: GoM vessel contracts; 99% recycling/repurposing in North Sea decom
A decommissioning project carried out by DOF Subsea on behalf of Repsol Sinopec Resources UK has achieved a 99% rate for the combined recycling and repurposing of recovered materials, while in the US, DOF Subsea has won multiple contracts for CSV Ross Candies
DOF’s decommissioning project was to manage and provide engineering, preparation, removal and disposal (EPRD) services at the Buchan and Hannay fields in the central North Sea. Offshore work, which was carried out over 74 days using DOF Subsea’s Skandi Acergy and Skandi Skansen vessels, saw the recovery of 135 concrete mattresses weighing approximately 800 tonnes, more than 12 km of rigid pipelines, SSIV/PLEM structures, 15 km of flexibles and umbilicals, spoolpieces, and around 1,500 grout bags and general debris.
The material was shipped to Aberdeen Harbour’s Clipper Quay for dispersal, with 95% of the material being recycled and 4% being repurposed. DOF Subsea reported that 1% was sent to a landfill ’as a last resort’.
In the US Gulf of Mexico, the 2010-built multipurpose construction support vessel Ross Candies won multiple contracts on projects that will see the vessel employed into the third quarter of this year.
"The vessel will be utilised well into Q3 2022, undertaking jumper installations, span remediation, pre-commissioning, decommissioning, pipelay support and IMR activities at multiple field locations in the Gulf of Mexico," DOF said in a statement.
On the decommissioning and recovery project, DOF said that 15 concrete mattresses were repurposed into aggregate and used in the roads at the Aberdeen Harbour extension project. Plastic sheaths from the flexible risers and umbilicals were recycled by an approved supplier and all metal was smelted.
DOF Subsea said it worked closely with Scotoil Service in Aberdeen throughout the process with any naturally occurring radioactive contaminated waste in metals or plastics removed by high-pressure cleaning at Scotoil before undergoing high-temperature incineration. The decontaminated metals and plastics were then recycled.
DOF Subsea executive vice president Atlantic region, Jan Kristian Haukeland commented, “This project is a demonstration of the DOF Group’s capability to use our fleet of world-class vessels to deliver turnkey solutions to the subsea energy sectors, in this instance a decommissioning scope for a key repeat customer.”
This was the second decommissioning project carried out by DOF Subsea on behalf of Repsol Sinopec in the Buchan and Hannay fields. In 2019, the company carried out EPRD services which included the 124-tonne Mid-Water Arch, still one of the largest structures ever decommissioned through Aberdeen Harbour.
Repsol Sinopec head of decommissioning Luis Batalla said, “We are delighted with this outcome as part of one of our biggest subsea decommissioning projects in the North Sea to date.
“Our decommissioning strategy is focused on efficiency, performance management, innovative contracting models, technology development and fit-for-purpose design which aligns well with DOF Subsea and its way of working.”
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