Precise takes an in-depth look at Pieter Schelte, the world's largest crane ship, that is revolutionising oil rig removal.
Question: How large does a ship have to be to be able to lift an oil rig out of the water? Answer: The same size as the Empire State Building. And that’s exactly what took to the seas last week from its home in South Korea to the Netherlands.
The Pieter Schelte has so far cost around $2.97bn, is 124m wide and 382m long. She’s capable of lifting 48,000 tonnes and can accommodate 571 people.
The ship (ed: ok, we know she doesn’t propel herself so a lot of nitpickers are questioning whether she can be classed as a ship, but we’re more interested in what she does so we’re not going to get hung up on that!) was commissioned by the Swiss company Allseas; and as well as taking platform removal to a new degree, she’s believed to be the world’s largest pipelay vessel – taking the title from Allseas’ other ship Solitaire.
The colossal ship is heading to the Port of Rotterdam where a special pit will be drained to house her while final assembly is carried out onboard. Once complete the world will watch as she attempts to remove each of Shell’s three Brent platforms slated for decommissioning – in a single lift. If all goes to plan, Shell have secured the option for the Pieter Schelte to remove a fourth.
The beauty is that she has been designed to lift the huge oil rigs in one go – removing the need for multiple cuttings and liftings that are currently required. Allseas has described how the work is carried out. Before the Pieter Schelte arrives, the legs of the topside support structure are cut. Then when she’s on scene, hydraulic clamps are deployed to lift the rig. These are attached to eight lifting beams at her bow which are set to the exact dimensions of the platform’s legs. There’s no way to stop the waves that’ll rock the ship but Allseas is using a motion compensation system which will enable the clamps to be motionless relative to the platform. Then it’s a relatively simple process of lifting the platform and the Pieter Schelte takes it to the Seaton Port of Able UK at Teeside where they’ll be dismantled.
The future, if things go as planned, is rosy for Allseas. Ben Wilby from energy research group Douglas-Westwood says it could corner the market in platform removals, telling DecomWorld, “There’s nothing else quite like it and it saves so much work…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.”
Clearly this is what Allseas is aiming to achieve, as it is already planning the Pieter Schelte’s little (but much, much bigger) sister. The as-yet unnamed vessel will be capable of lifting 77,000 tonnes and should be ready by 2020.