DOF Subsea hits 99% repurpose rate on latest decommissioning project

DOF Subsea has achieved a 99% rate for the combined recycling and repurposing of recovered materials on its decommissioning project at the Buchan and Hannay fields in the Central North Sea.

The offshore works, carried out using Skandi Acergy and Skandi Skansen, included the recovery of 135 concrete mattresses weighing approximately 800 tons, more than 12 kilometers of rigid pipelines, SSIV/PLEM Structures, 15.5 kilometers of flexibles and umbilicals, spool pieces, and around 1,500 grout bags and general debris.

The material was shipped to Aberdeen Harbour’s Clipper Quay for dispersal, with 95% of it being recycled and 4% being repurposed, and only 1% sent to landfill as a last resort.

According to DOF, the recovered material was dispatched for a wide variety of uses. A total of 15 concrete mattresses were repurposed into aggregate and used in the roads at the Aberdeen Harbour extension project. The plastic sheaths from the flexible risers and umbilicals were recycled by an approved supplier and all metal was smelted.

The company collaborated with Scotoil Service in Aberdeen throughout the process with any NORM 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.

“We are delighted with this outcome as part of one of our biggest subsea decommissioning projects in the North Sea to date,” said Luis Batalla, head of Decommissioning at Repsol Sinopec.

“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.”

This was the second decommissioning project DOF Subsea carried out on behalf of Repsol Sinopec in the Buchan and Hannay fields.

In 2019, the company performed EPRD services which included the 124-ton Mid-Water Arch (MWA), one of the largest structures ever decommissioned through Aberdeen Harbour. The project also included the recovery of risers and all associated equipment, achieving a combined recycling and repurposing rate of 97.7%.

Repsol Sinopec filed its draft decommissioning plans for the Buchan and Hannay fields to the UK authorities in March 2020.

Decommissioning in the fields started in 2017 with the off-station and onshore recycling of the Buchan Alpha platform, which was completed at Dales Voe in Lerwick Shetland, after ceasing production as planned in 2017 – after 36 years and almost 150mm barrels of oil produced.