Festooned with cranes, oil pipelines and manned by a crew of several hundred, the Pioneering Spirit sits in the port of Rotterdam like a giant marine version of a forklift truck.
World’s largest ship:
Next month this vessel, one of the world’s largest ships, will arrive in the North Sea and attempt to remove the 24,500-tonne top of a Shell oil rig installed during the oil boom years of the 1970s. If successful it will be the heaviest ever single lift of a rig’s “topside”, and only the second by this purpose-built $3bn (£2.4bn) ship.
Dedicated to oil rigs:
More than 100 rigs are due to be decommissioned in UK and Norwegian waters over the next 10 years at a cost of billions to oil companies and taxpayers. The dismantling of the Delta rig in the Brent oil field is not the first such job in the UK but is believed to be the biggest.
Stress on recycling and sustainability:
“If you remember back to the 1970s, there was not a lot of thought to decommissioning, or recycling and sustainability,” said Alistair Hope, general manager for Shell’s Brent decommissioning project. He described the field as a “prolific national asset”, having produced £20bn in tax for the Treasury over its lifetime.
Task decommissioning an humongous hurdle:
Shell, burned in 1995 by the furore over its decision to sink the Brent Spar storage buoy at sea, is acutely aware of the need for the clean-up to go smoothly.
Hope called the task of decommissioning the field an “enormous challenge”, due to its remote location – the closest railway station is in Bergen, Norway, nearly 150 miles away – and complex nature of the installation.
In preparation for next month’s operation machines have been used to cut Delta’s 18-metre diameter concrete legs above the water line. Workers have welded and strengthened the topside so it does not disintegrate when picked up.
In the past, the idea of removing such a huge structure in one go would have been unthinkable.
The Pioneering Spirit leaves Rotterdam for trials:
However, the Pioneering Spirit is the product of decades of work by Allseas, its Dutch-Swiss owner and one of the world’s two biggest oil pipeline laying companies. The unique design of the ship, built over three years in a South Korean shipyard, will be key to removing Delta and the other rigs among the 470 North Sea oil and gas installations in UK waters.
6 jumbo jets long:
The scale of the vessel is dizzying. Six jumbo jets long, it is powered by eight engines. At the stern, welders are training in preparation for the next job after Brent – that of laying a gas pipeline from Russia to Turkey.
Towards the bow are eight pairs of arms, weighing 2,000 tonnes each. Inside, they are crammed with bespoke hydraulic pumps, compressors and other equipment.
Fast lift technique:
Once the ship has aligned itself with the Delta rig, huge pistons will push the arms, one at a time, underneath the topside. A GPS system and 12 propellers will make minute adjustments that in theory should keep the ship in place whatever the wind and waves throw at it.
The arms will be attached to the rig’s topside, taking about 80% of its weight. Finally, the rig will be removed with a “fast lift”, akin to a snatch by a weightlifter.
Interview with Duncan Manning of Shell:
Edward Heerema, president of Allseas, said: “The fast lift is to make sure you don’t have a re-impact of the topside on the base, which you might have with a big wave. It is done with a tremendous amount of compressed air.”
Minimal human assistance required:
The whole process is overseen and controlled by just a handful of people on the Pioneering Spirit’s bridge, monitoring activity with numerous cameras and sensors.
But while the ship’s first lift of a Norwegian platform last year was performed successfully and safely, crew aboard the vessel also admit there were teething problems later fixed.
Minimum risk expected:
Shell and Allseas are confident they have kept any risk on Delta to a minimum. They have done two test lifts on a mini-rig off the Dutch coast, once in clement August weather and another in November swells last year.
“We’ve worked on preparations for such a long time, we don’t see a spot to worry particularly about. Of course, when things go wrong they come from an unexpected angle,” said Heerema. At worst he anticipates a delay of a day or so. The lift operation, if all goes well, should take a day.
Arrival in May:
Ultimately, the metal from Delta is destined to arrive on about 12 May at a Hartlepool scrapyard run by Able UK. Peter Stephenson, the demolition company’s founder, has spent £28m strengthening the quay where about 50 workers will spend a year recycling 97% of the metal.
Not everyone is so happy about the Brent plans. Green groups including WWF and Greenpeace this week warned of “insufficient information” from Shell and a failure to adhere to international standards set up in the wake of the Brent Spar incident. The company says it will listen – but it looks unlikely to change course.
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Source: The Guardian