The two parallel Nord Stream pipelines each have a capacity of 27.5 Bcm/a; the first line began operation in November 2011, and the second line is scheduled for start-up later this year, its construction having been completed in early April.
Fabricated from high-tensile X70 grade steel, the twin pipelines will run under the Baltic Sea from the Russian coast near Vyborg, to the German coast near Greifswald. Gas transported by Nord Stream will provide an estimated 25 per cent of the extra imports needed in the European Union by 2030.
Headquartered in Zug, Switzerland, Nord Stream AG was established to design, construct, and operate the pipeline. The project shareholders are Gazprom, with a 51 per cent stake, German companies Wintershall Holding AG and E.ON Ruhrgas AG, each with a 15.5 per cent stake, Dutch firm N.V. Nederlandse Gasunie with a 9 per cent interest, and French firm GDF Suez with the remaining 9 per cent interest.
Work on the Nord Stream Pipeline began in April 2010, and since then, three major pipelay vessels have been involved: Saipem flat-bottomed pipelay vessel Castoro Dieci and Allseas’ Solitaire worked on laying specialist parts of the route including the landfalls and laying in the Gulf of Finland, respectively, while the majority of the pipelaying has been undertaken by Saipem’s semi-submersible Castoro Sei.
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The Castoro Sei was launched in 1978; the translation of the first part of her name into English is ‘beaver’ and the animal’s reputation for tenaciousness has been replicated by the vessel which, since its launch, has been involved in the construction of many of the world’s major offshore pipelines.
Owned and operated by Saipem, the vessel, which Pipelines International was able to visit recently, is positioned during pipelaying using a 12-point mooring system, the on-board winches of which are used to pull the vessel sternwards as the welded pipe emerges from the stinger at the bow. Four (or more) anchor-handling vessels are needed continuously to relocate the anchors on the seabed to which the vessel is attached; the on-board positioning system which is controlled with great precision, is used to establish the positions of the anchors and the tensions provided by the vessel’s winches. On board, the pipe is double-jointed into 24 m lengths, and then welded to the mainline in a large hall known as the ‘cathedral’, in which each length is aligned with care.
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