LEIDEN, the Netherlands – Heerema’s semisubmersible crane vessel Sleipnir has completed the single-lift removal of Shell’s 10,100-metric ton (11,133-ton) Brent Alpha platform jacket in the UK northern North Sea.
According to the company, this single jacket lift breaks the Sleipnir’s recent record for lifting the 8,100-metric ton (8,929-ton) Jotun-B jacket.
The Sleipnir arrived at the Brent field 186 km (116 mi) northeast of Scotland’s Shetland Islands on July 23, 2020 and completed the project by offloading the jacket onto the quayside at the AF Miljøbase decommissioning site in Vats, Norway on Aug. 11, 2020.
The company said the jacket removal presented novel challenges that resulted in unique solutions. During the project, Heerema cut jacket legs at 7.3 m (24 ft) diameter using a 288-in. diamond wire cutting tool developed alongside CUT UK, especially for the Brent Alpha removal. This is the largest leg diameter to have been cut this way, the company claimed.
Also, during this project the company removed and transported the conductors with the jacket, a new way of decommissioning, it claimed. The conductors were suspended on a Heerema Fabrication Group built conductor hang-off frame made for this project.
The Brent Alpha jacket will end its lifecycle by being more than 97% recycled.
This project is the Sleipnir’s fourth decommissioning job this summer. So far, the vessel has removed and transported more than 43,900 metric tons (48,391 tons) of decommissioned offshore infrastructure for recycling over this summer campaign.
Later this year, the Sleipnir will install Dana Petroleum’s P11-Unity platform in the Dutch North Sea.