Decom World: North Sea decommissioning: could the mega vessel Pieter Schelte do it all?

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Posted by Rod Sweet [1] on Jul 23, 2014

With the largest lift vessel in the world and an even bigger one on the way, could Allseas Group absolutely corner the platform removals market?

With the clock ticking to May 2015, when the world will see the new vessel Pieter Schelte try and remove each of Shell’s three Brent platforms slated for decommissioning in a single lift, the question is being asked – if this works, will operators remove their platforms in any other way in the future?

In August last year Shell UK awarded the Swiss-based Allseas Group SA the contract for the removal and load-in to shore of the topsides of three of its Brent platforms, with an option to do the same with the fourth platform.

Allseas Group will use the gargantuan Pieter Schelte, a 382-metre-long, twin-hulled, dynamically positioned vessel specially designed for heavy single lifts, now nearing completion at South Korea’s Daewoo Shipbuilding and Marine Engineering. It can remove topsides weighing up to 48,000 metric tons in a single lift where before, multiple cutting and lifting operations would be required.

Allseas has described how the largest vessel of its type in the world will do the job. Before it arrives on site the legs of the topside support structure are cut. When it rolls up, hydraulic clamps mounted on eight horizontal lifting beams at the vessel’s bow will have been adjusted to the exact dimensions of the platform legs.

Waves will rock the boat during the crucial operation but, thanks to its motion compensation system, the clamps will be motionless relative to the platform.

Once the clamps are connected, tension in the lift system is gradually increased to transfer the weight of the topsides from the jacket to the vessel. Then comes a rapid, 2-metre lift to free the topsides from the jacket, and the Pieter Schelte starts making its way to the Seaton Port of Able UK at Teeside, England, where the platforms will be dismantled.

With the simplicity of the operation and the time and cost savings Shell can expect, it raises the question: can Allseas absolutely corner the platform removals market? Ben Wilby, researcher at energy research group Douglas-Westwood, believes it’s possible.

“With large platforms at the moment I think they’ve definitely got an opportunity there because there’s nothing else quite like it, and it saves so much work,” he told DecomWorld. “For an operator to call someone up and say, can you come and do it in one lift, rather than spending months cutting bits off – to my knowledge, no other company is developing this sort of equipment.”

Allseas has clearly contemplated the possibility because, before the Pieter Schelte was even constructed, it announced last year that it was building something even bigger. Scheduled for completion in 2020, this as-yet unnamed vessel will have a lift capacity of 72,000 t, making it able to remove anything in the North Sea.

“It’s certainly aggressive,” said Wilby. “They’re obviously very confident that it will be a success. There was a lot of scepticism when they announced they were building it, but this is them showing how confident they are. With the specs they announced the new vessel will be able to pretty much lift everything in the world.”

Allseas’ commitment to innovation is impressive. It launched the Pieter Schelte concept way back in 1987 and refined it over the next 20 years. It began ordering long-lead items for its construction in 2007, and the vessel will finally be ready later this year.

But there are questions still to be answered about how it will make its investment pay. Allseas has admitted, Wilby said, that pricing projects like the Brent platforms removal is difficult.

“They have to spend months and months planning how it’s all going to go,” he said, “but then they can turn up and in a couple of days have the job done. So I think they’re not entirely sure how to price contracts to make it attractive but also to give value to themselves.”

There is also the question of where in the world it can sell its services, apart from the North Sea. “The Gulf of Mexico is probably the biggest decommissioning market,” Wilby said, “but they tend to be very small platforms so you wouldn’t need a vessel like this.”

Nevertheless, if there is a first-mover advantage to be had, Allseas will get it. In a conservative sector, would-be competitors are wary of making such large investments until they have seen the concept work, Wilby said. A year from now, depending on how the Brent project goes, companies may be wishing they’d started earlier.

Overall, the whole decommissioning landscape could change radically.

“As long as they get the pricing right and as long as there are no disasters with their early projects, I can’t see why it wouldn’t,” Wilby said. “There are quite a lot of large platforms that are getting to the end of their design life and if [operators] see a vessel that can do it all in one go I don’t know why a company wouldn’t use them rather than more awkward, smaller vessels.”
Special thanks to Richard Charter

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