The platform decommissioning and recycling project involved three years of preparation, including structural modifications and offshore work, culminating in a 14-second lift.
Allseas Pioneering Spirit vessel has completed a single-lift removal of the 15,300-mt topsides from the Heather Alpha platform, 460 km northeast of Aberdeen in the UK northern North Sea, according to an Aug. 14 Allseas news release.
It was the largest planned single-lift operation in the North Sea this year, according to a separate Aug. 14 press release by EnQuest, operator of the Heather Field.
The 14-second lift followed three years of detailed engineering, planning and offshore preparation under a collaboration between EnQuest and various contractors.
Allseas started its preparations for the task last year, installing custom-made lift points on the topsides, also performing structural strengthening, caisson works and separation cuts. Much of this activity took place while the platform was still manned.
Early this year, Allseas’ teams returned to complete the underdeck scopes related to leg cutting and separation.
The teams worked alongside specialist rope access crews to address weather and operational constraints to keep the project on schedule.
“Pioneering Spirit completed the lift in around 14 seconds, but that astonishing reality was only made possible by three years of meticulous planning, engineering and preparation works.
After almost 50 years of operations in the North Sea, Heather Alpha’s legacy is to be an exemplar of a best-in-class decommissioning project, from inception to the responsible recycling of its materials.”
—EnQuest Decommissioning Director John Allan
The topsides were due to be transferred to Allseas’ Iron Lady cargo barge for towing to the M.A.R.S. disposal yard in Frederikshavn, Denmark. There, the structure will be dismantled, with more than 95% of materials and other items set to be recycled and repurposed.
Heather Alpha was an integrated drilling, production and living quarters platform. According to the UK’s North Sea Transition Authority, the topsides comprised three decks, supported by an eight-legged tubular steel frame jacket in 143 m water depth.
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