Topsides removal a milestone in decommissioning of Dunlin Alpha

June 23, 2022
HAF Consortium safely removed topsides from Fairfield Energy’s Dunlin Alpha northeast of Shetland.

Offshore staff

LEIDEN, Netherlands — The topsides have been removed from Fairfield Energy’s Dunlin Alpha.

Heerema Marine Contractors and AF Offshore Decom, operating as the HAF Consortium, safely removed about 19,000 metric tons over two campaigns to successfully deliver the platform for reuse and recycling, according to a June 17 Heerema news release.

The offshore operations started in early April, with Thialf and the Heerema and AF Offshore Decom teams executing hook down and preparatory activities.

Thialf removed about 3,500 metric tons of modules to its deck and transported these to the AF Offshore Decom Environmental Base at Vats, Norway.

The hook down activities were optimized to maximize the final lifting weight of the module support frame (MSF) to fully utilize Sleipnir’s lifting capacity. After the successful hook down, Sleipnir returned to the field on May 31 and transferred five modules weighing about 3,500 metric tons in total to its deck.

Thereafter, the MSF rigging was prepared, weighing in at almost 550 metric tons, and connected to the purpose-built pre-installed lift points.

As the MSF was initially installed using a floatover method, this was the first time the structure was lifted. In an industry first, Sleipnir then removed the 11,750 metric ton MSF in a single lift before transferring it to quayside suspended in the vessel’s cranes.

The Dunlin Alpha installation, located approximately 137 km northeast of Shetland and in a water depth of 151 m, produced its first oil in 1978. In the 37 years that followed, more than 522 MMbbl of oil were recovered from the Greater Dunlin Area, comprising the Dunlin, Dunlin S/W, Osprey and Merlin fields. Fairfield Energy acquired the assets in 2008 and took over full operatorship in 2014, maximizing production during its late-life stage and then progressing its subsequent decommissioning programs.