After 20 years as an idea, the Pieter Schelte heavy-lift and pipelay vessel is getting close to winning its first work, with the North Sea its most likely first customer. Elaine Maslin shares a look.Big just got bigger, and what was once a dream is getting closer by the day to becoming reality.
Big just got bigger, and what was once a dream is getting closer by the day to becoming reality.
It is Allseas’ mega-vessel, the Pieter Schelte, which over the past year has been taking shape in Daewoo’s South Korean docks – as have talks with operators, including Shell, over its potential first application.
The twin-hull, €2.2billion vessel is a behemoth at 382m long and 124m wide. It was designed to make a significant impact on the heavy lift capability currently available in the global offshore market, both for platform installation and decommissioning; and pipelay with its 2000 tonne (2205 short tons) tension capacity S-Lay pipelay package.
Its lift capability is given as an eye-watering 48,000 tonnes (53,000 short tons) for topsides and 25,000 tonnes (27,500 short tons) for jackets.
However, following the construction and then provisional joining of the two hulls at the end of last year, the firm decided to increase the width of the vessel’s unique slot between the two hulls, to be used for installing or removing topsides, by 7m, to 59m (193ft). The portside hull will enter the floating dock this month (May) to allow for the erection of the widening blocks. In mid-July, the two hulls will be re-joined afloat.
While slightly delaying its final completion, the move will improve Pieter Schelte’s capacity, still well before Shell’s North Sea Brent decommissioning project.
Edward Heerema, Allseas’ president and the creator of the Pieter Schelte concept (named after his late father, a pioneer of offshore heavy lifting) explained: “We determined the width of the slot a long, long time ago, 20 years ago, and in those days we established that the widest docks available were 120m wide. We did analysis of the platforms that had to be taken away and we did not get very accurate information from the oil companies in those days, so we underestimated the width that was needed. Because of the limitations of the building docks in those days we decided that the vessel could not be wider than 117m with a slot width of 52m.
“But during studies over the past two years for clients we have received very accurate information and we saw that the slot width should be increased. We also realized that the dock width at Daewoo was actually 134m - a lot more than available a long time ago.”
It is an evolving project. Edward Heerema’s concept for the Pieter Schelte was first launched in 1988, just three years after he started Allseas. Even until recently, the firm has still been finalizing designs – the tilting lift beams for jacket removal and installation, which lift, tilt and then lay down jackets, will not be installed until a year after the vessel is launched, due to Edward Heerema wanting to get them right.
“This ship, novel in every respect, has required from us years and years of analysis work,” he said. “But because it represents so great a cost, we have to do it right the first time. It is an engineer’s paradise; the fun is to solve it.”
The vessel’s concept is the use of eight sets of horizontal lifting beams across its slot for removal or installation of topsides. They have a motion compensation system in order to be able to operate in rough seas. The vessel will have two tilting lift beams on the stern, and laydown space for the installation or removal of jackets. It will be powered by eight main diesel generators, providing a total installed power of 95 MW (megawatts), powering 12 azimuth thrusters.
For pipelay, it will handle 12-m pipe sections held under tension by four 500 tonne (550 short ton) tensioners with a 170 m (558ft) long stinger supporting the pipe as it leaves the vessel.
Between summer and December last year, the two hulls were composed separately from sections partly built in China, also by Daewoo, in two floating dry docks in South Korea before being towed out into open water, to be provisionally welded together. The combined hull, complete with its current 52m slot, was then brought into a single larger floating dry dock.
The vessel’s 12 thrusters – at 75 tonnes (83 short tons) a piece - have been delivered to the yard and construction of the lifting beams, including eight 200-tonne (220 short ton) clamps, which will straddle the slot, is underway.
“So much has happened between the summer and December,” said Edward Heerema, “providing fascinating pictures.”
Work finding a first customer for the Pieter Schelte has also been progressing.
“The timing of the construction of the Pieter Schelte, with its delivery late 2014, fits in beautifully with the timing of, for example, the Brent decommissioning program,” said Heerema. “The first project might be the removal of the Shell Brent platforms.”
The Brent Delta platform reached “cease of production” (COP) in December 2011. Brent Alpha and Bravo are currently scheduled to reach COP in late 2014, with the Brent Charlie COP date scheduled beyond 2015.
The work scope, should Allseas win it, would be for the removal of the four topsides and one jacket structure – the other three are concrete gravity-based structures which will be left in field under a derogation order.
“Shell has studied our ship for two and a half years,” said Edward Heerema. “They had us do very serious and thorough studies, so Shell has got to know our vessel and its capabilities in and out. They have had their best people evaluate what the ship could do.
“It would be a great entry for us and for the business. Having an award for platform removal changes our whole position. Over the many years we went through the phases that this vessel was just a story, a nice intention. Then came the phase of designing it in detail, building it, and now it is for real. We are very hopeful of the Brent project.”
Heavy-lift work of this type would be the Pieter Schelte’s primary target market, being able to do what smaller heavy lift vessels currently do in a modular fashion, taking more time.
The North West Hutton topsides decommissioning project, for example, involved 58 separate moderate and heavy lifts, and about 100 days of heavy-lift vessel time. The semi-submersible vessels being used are certainly cheaper per day, admits Edward Heerema, as they have already paid off their capital costs.
Because the market for very large heavy lifts is limited, the Pieter Schelte will also be looking for new platform installation work, to make sure it is sufficiently utilized. There is not sufficient heavy lift work to be occupied a significant part of the year, which is the reason for adding the pipelay capability.
“There are also new elements in the market, such as the installation of 10,000-15,000 tonne (11,000-16,500 short ton) transformer stations for wind energy,” said Heerema. “They are just odd projects, not frequent, but they give us added work.”
Heerema said that because of the capabilities of the Pieter Schelte, oil and gas operators would also be able to consider single lift installation of platforms, meaning far less hook-up work offshore.
“So far they have to design to the capacities of the largest semi-submersible heavy lift vessels, which is about 11,000 tonnes (12,200 short tons) at the required outreach of the cranes,” he said. “Now they can consider whether they want to lift bigger units in one, which gives them savings on hook up costs – they can put together more of the platform onshore before it goes offshore.”
The Pieter Schelte’s capacity will also challenge the yards who could receive the immense structures it will handle. A 200m (656ft) long cargo barge is being built to help transfer structures when the vessel cannot line up directly on the quayside. All big fabrication yards in the UK and Norway will be able to take the barge, said Heerema.
However, some yards will need to make upgrades to take the work.
“They need load spreaders and beams (for the weight of larger structures), they have to have big cranes to take the structures all apart and they need to mobilize sufficient man-power to do all that work,” said Heerema.
“Most have sufficient area; their question is mainly quayside strength. Some need to drive piles in the quayside area.
“It does take some initiative on the side of fabrication yards, but the response has been positive. They will find answers. We think with them, we try to come up with solutions that are practical for them and for us to skid from the cargo barge onto the quayside in one movement.”
Thanks to the extra work on Pieter Schelte, the dismantling yards now have until late 2014 or early 2015 to get ready.
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