Shell is likely to rule out most of the proposals it has received for the onshore disposal of the Brent Spar storage buoy because of fears that the structure would collapse, the company’s head of decommissioning said this week.
Eric Faulds, decommissioning manager at Shell UK Exploration and Production, said four of the six proposed alternatives to dumping the Spar at sea would stress the steel structure beyond the point of elasticity into a ‘plastic’ regime, close to the point where it could collapse. ‘In the end, there could be some risks we will not accept because the threat of loss of life is too great,’ said Faulds.
He said that Shell generally only accepted ‘plastic’ modes in offshore structures for exceptional events such as a ship colliding with a platform not for the engineering base case.
‘That collapse analysis is very difficult to do using computers,’ he said.
The analysis of the six proposals carried out by the Norwegian certifying authority Den Norske Veritas determined that four carried high technical risk. These were the two schemes put forward by the Kvaerner Seaway Spar Alliance, and the ones from McAlpine Doris Able.
DNV said the other two proposals would be far more expensive than deep-sea disposal priced at £4.7m. Brown & Root’s plan to up-end the Spar and tow it to Scotland for dismantling is priced at £48m. Wood-GMC’s scheme to raise it vertically and cut the hull into rings for use in a quayside is costed at £21.5m.
The B&R and Wood-GMC proposals would also carry a considerably greater risk of loss of life 9.5 and 2.5 times higher respectively.
But both would be more environmentally beneficial, in terms of the net energy expended. Heinz Rothermund, Shell Expro’s managing director, said the company would consider all factors before a decision is made at the end of the year.
The company will present all six proposals and DNV’s analysis of them to interested parties at seminars in London, Copenhagen, Rotterdam, and Hamburg over the next month.