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The pipelay of the longest subsea pipeline in the world has started

April 22, 2005, 11:10 CEST

Friday the semi-submersible barge LB200 started the pipelay of the longest subsea pipeline in the world stretching 1,200 kilometres between Nyhamna in Mid-Norway to Easington in Great Britain. From 2007, Ormen Lange can supply up to one fifth of the UK's gas requirements for decades to come.

More than a million tonnes of steel will be used, and the production of pipes will lay claim to a third of the world’s total production capacity for this type of pipeline.

100,000 pipes in all will be painted inside and covered with asphalt and concrete before installation in the North Sea. This will require over a million tonnes of concrete and 25,000 tonnes of steel reinforcements.

Two of the world’s largest pipeline-laying vessels, Stolt Offshore’s LB200 and Solitaire from Allseas, will lay the 1,200 kilometre long pipeline, Langeled, between Aukra and Easington, in addition to the pipelines from the field to the onshore processing plant.

LB200 has started the pipelay from the Sleipner platform in the North Sea and is heading south towards Easington. Solitaire will start laying the first 33 kilometres of Langeled and the production lines from Nyhamna in the beginning of June. The main part of the northern leg of Langeled will be installed next year.

Hydro has designed the Langeled pipeline to carry more than 70 million cubic metres per day – meaning the Easington terminal could be providing more than 20 percent of UK gas needs for decades to come.

Ormen Lange project well underway
A group of Norwegian and international companies are already well underway with the construction of Ormen Lange, and later this spring a series of new activities will begin both onshore and offshore.

FMC Kongsberg are currently manufacturing production equipment which will be placed on the seabed in the fall of 2005, while at Grenland-Group’s yard in Tønsberg, the enormous underwater installations are taking shape, measuring 44 by 33 by 15 metres.

Just after Easter the manifolds was raised onto the template frames, and by August, the production stations will be installed 900 metres below the surface in the Ormen Lange field, using one of the world’s largest lifting vessels, Thialf from Heerema.

The offshore-to-land pipeline has to pass the Storegga slide area with its rocky undersea landscape before climbing the steep escarpment.

To reduce the number of lengths of suspended pipeline, a complex route through passageways and with curves around obstacles has been chosen, so that the pipes can be laid in the least problematic terrain.

At the same time, the seabed is being prepared for pipe laying, both by excavating and filling aggregate.

Excavation at depths of 1,000 metres
The aggregate-laying vessel Tertnes from Von Oord has resumed work on creating support for the pipeline so that spans longer than 50 metres are avoided. Last year about 400,000 tonnes of stone were installed, but nearly 2 million tonnes remain to be laid.

The project is also receiving excellent assistance from Nexans' Spider technology. Two newly developed, remote-controlled underwater excavating machines will prepare the seabed before pipe-laying can begin on the steep slopes and broken terrain far below the sea surface.

This work will begin in April this year and continue until the autumn. Nexans also have the option to carry out localized pipe burial after installation in 2006 and 2007.

A pioneering project
Ormen Lange is a pioneering project on the Norwegian Continental Shelf. The field lies in an area of the Norwegian Sea with climatic and oceanographic conditions that make Ormen Lange one of the world’s most demanding gas development projects.

The combination of great sea depths, highly irregular seabed terrain, strong underwater currents, sub-zero temperatures and challenging wind and wave conditions, have imposed considerable challenges on all parties involved in the project.

Development operator Hydro has mobilized significant portions of the Norwegian research community together with Norwegian industry in order to find solutions to problems far more complex than those previously encountered in oil and gas development projects on the Norwegian Continental Shelf.

Hydro is the development operator for both Ormen Lange and Langeled. Statoil has the management of the Langeled project in cooperation with Hydro.

Important milestones ahead

  • April: Nexans will commence work on the seabed. The contract entails excavation and removal of mass in pathways for pipelines and cables in broken terrain between the Ormen Lange field and Nyhamna. Two newly developed, remote-controlled underwater excavators, so-called Spiders, will carry out excavations in steeply inclined seabed terrain in deep water off the Storegga slide. This work will start in April this year and continue until the end of the autumn. The Spiders will be operated from the vessel Geobay. Nexans play an important role in the work on the world’s possibly most demanding pipe-laying project.

  • June: Pipeline pull-in to Easington.

  • June: Solitaire will start pipe laying from Nyhamna, beginning with pull-in. This will be a spectacular sight, since the ship with the stinger is as long as five jumbo-jets.

  • August: Thialf, the world’s largest lifting vessel, will carry out installation of the underwater stations at 900 metres below sea level.

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