World's largest ship sets sail for UK: As big as six football pitches and twice as long as an aircraft carrier, it will ferry a 24,000 ton oil rig 500 miles to shore

World's largest ship sets sail for UK: As big as six football pitches and twice as long as an aircraft carrier, it will ferry a 24,000 ton oil rig 500 miles to shore

The largest ship in the world arrives in the North Sea next month to start dismantling an oil rig, in an unprecedented engineering mission.

The Pioneering Spirit –longer than six Boeing 747s and nearly twice the size of the Royal Navy's new aircraft carriers – will prise the 24,000-ton top platform off Shell's Brent Delta rig and lift it on board.

It will ferry the 230-square foot structure – helipad included – intact for nearly 500 miles trip through to the Able UK yard in Teesside where it will drop it off to be recycled.

If successful, the mission will mark a key step in winding down the Brent field, which has supplied around 10 per cent of the UK's oil since it was discovered in the 1970s but is coming to the end of its life.

Sea monster: The Pioneering Spirit is longer than six Boeing 747s and nearly twice the size of the Royal Navy's new aircraft carriers

What to do with the ageing rigs has been a conundrum for Shell and will only become more pressing as the North Sea declines. 

Rather than dismantling the platform offshore, Shell bosses have decided it would be safer, quicker, cheaper and more efficient to take it ashore, intact, where it can be taken apart.

Alistair Hope, project and technology director for Brent decommissioning at Shell, said: 'They [Brent platforms] are a nightmare to pull apart so it is far better to bring them ashore in one piece and dismantle them in a much more controlled way on the quayside.'

Designed by Swiss-Dutch Company Allseas Group, the Pioneering Spirit is the only ship that can do that on the scale Shell needs. 

Built between 2011 and 2014 in South Korea, she has a deck space equal to six football pitches and can carry up to 47,200 tons.

Yet her mission is extremely delicate, requiring movements controlled down to the inches. Sixteen giant steel arms will attach to points on the underside of the rig platform and lift it up. 

But she has to be able to do that in waves potentially nearly ten feet high, in as little as nine seconds.

Originally planned for last summer, the Brent Delta lift has been pushed back due to its complexity. 

Tests have been done in simulators and a special test rig in Rotterdam, where the Pioneering Spirit is anchored. Last summer she removed Repsol's Yme 13,300-ton platform from the Norwegian North Sea.

Edward Heerema, president and founder of Allseas, said he isn't worried about the upcoming job. 'We have been preparing for five years,' he says.

And with more than 470 North Sea platforms likely to need decommissioning by the 2050s, the effort is also being watched closely by the oil industry.

As it approaches the Able UK yard in Teesside, the Brent platform will be transferred onto a purpose built barge, the Iron Lady, before being slid onshore. 

It is hoped 3 per cent or less will go to landfill while the rest can be re-used or sold off for scrap. Yesterday in Rotterdam, the Pioneering Spirit's crews were working on final preparations for the lift.

'There was a lot of skepticism at the beginning,' said Allseas construction manager Daan Akerboom.

'But when you see it at work, it's unbelievable,' he said.