A North Sea decommissioning project based at Aberdeen Harbour hit just shy of top marks for recycling structures.
The Norwegian firm was picked to project managed and provide engineering, preparation, removal and disposal (EPRD) services at the two central North Sea assets.
Offshore works were carried out over 74 days using DOF Subsea’s Skandi Acergy and Skandi Skansen vessels.
A total of 135 concrete mattresses, weighing approximately 800 tonnes, were recovered, as were more than 7 miles of rigid pipelines, subsea isolation valve structures, about 10 miles of flexibles and umbilicals, spoolpieces, and around 1,500 grout bags.
It was all shipped to Aberdeen Harbour’s Clipper Quay for dispersal, with 95% of the material being recycled and 4% being repurposed.
That leaves just 1% that was sent to landfill as a last resort.
Of the material that was recovered, a total of 15 concrete mattresses were repurposed into aggregate, and used in the roads at the £350m 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 worked closely with Scotoil Service in Aberdeen throughout the process, with any contaminated waste by high pressure cleaning.
Jan Kristian Haukeland, DOF Subsea’s executive vice president Atlantic Region, said:”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.
“Focusing on our company values ‘Respect, Integrity, Teamwork, Excellence and Safety’ has enabled us to work with Repsol Sinopec to attain this impressive achievement, of 99% recycling and repurposing at Buchan and Hannay.”
This was the second decommissioning project carried out by DOF Subsea on behalf of RSRUK in the Buchan and Hannay fields.
In 2019, the company carried out EPRD services that included the 124 tonne mid-water arch (MWA), one of the largest structures ever decommissioned through Aberdeen Harbour.
That project also included the recovery of risers and all associated equipment, achieving a combined recycling and repurposing rate of 97.7%.
Luis Batalla, head of decommissioning at RSRUK said: “We are delighted with this outcome as part of one of our biggest subsea decommissioning projects in the North Sea to date.
“A truly collaborative and open communication approach was taken on this project between Repsol Sinopec and DOF Subsea and I have no doubt that this helped to facilitate the success and safe execution of this part of our decommissioning programme.
“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 their own way of working.”