 A MEETING OF GIANTS: "Solitaire" and "S7000" were floating side by side for a 24-hour period, next to the Storegga slide. Here, the "S7000" is to pick up and continue laying the production pipelines that "Solitaire" has laid all the way from Nyhamna down to the middle of the landslide, at a depth of around 550 metres. |
Several of the world's largest pipelay vessels are involved in installing the Ormen Lange project's gas pipelines. At present, two of them are meeting 100 kilometres off the coast of Romsdal in Western Norway, where pipelines are to be laid down the edge of an ancient landslide, as steep as the landing slope of Oslo's ski jump, Holmenkollen.
It is Hydro, operator for the development phase of the project, that – with the help of the huge vessels “Solitaire” and “S7000” – is in the process of making new oil and gas history, by carrying out one of the most demanding development projects in the world.
Great sea depths, an uneven sea floor and powerful currents, combined with subzero temperatures, extreme wind conditions and enormous waves make Ormen Lange a complicated project.
But Hydro and the engineering company Reinertsen have spent several years becoming familiar with the seabed, and finding the optimal pipeline route between underwater peaks and troughs, along the floor of the continental shelf and down the steep, 35 degree incline of the Storegga slide area.
The sea floor has been meticulously examined by an unmanned, self-motored submarine, and by remote operated vehicles (ROVs), and the engineers know large areas of the seabed down to every last detail. In addition, hundreds of acoustic transmitters and receivers have been placed on the sea floor, which enables marine operations to be carried out with centimetre precision.
First part of pipelaying operation complete
Allseas’ pipelay vessel “Solitaire” will today complete its part of the pipelaying operation, for the first of the two production pipelines running from the land-based facility being built at Nyhamna out to the Ormen Lange field. Some way down the edge of the Storegga slide area, 100 kilometres offshore, Saipem’s pipelay vessel “S7000” has to take over, in order to lay the last 20 kilometres of pipeline using a different method. This last section is particularly demanding, since it continues down the edge of the ancient landslide, all the way down to the well templates at a sea depth of 850 metres.
Since this last stretch is so steep, the “S7000” will lay the pipelines in a “J” formation – that is to say, the pipelines will be welded together in groups of four, then laid from a 130-metre high tower fixed to the stern of the vessel (13 metres higher than Norway’s tallest building, the hotel Oslo Plaza).
The “Solitaire” is 425 metres long, including its 65-metre long pipelay ramp, and has a crew of 400. The vessel has dynamic positioning, which means that it does not need to be anchored during operations. The “Solitaire” has six welding stations along the length of the ship. The pipes are welded together both inside and out, before a protective coating is added, prior to an ultrasound control of the quality of the welded joint.
The “S7000” – originally a crane ship – is almost 200 metres long, and is equipped with a 130-metre high vertical tower for pipelaying on Ormen Lange. This vessel also has dynamic positioning so that it does not need to be moored or anchored during the pipelaying operation.
Many vessels involved
In addition to these two colossal ships, various other vessels are operating close to the Ormen Lange field. In 2006, a total of 2,600 vessel-days will be required in order for all the pieces of the gigantic Ormen Lange project to fall into place. This includes everything from the giant pipelay vessels to smaller survey boats and cargo vessels used for transporting pipes.
The survey vessel “Geobay” will assist in installing the pipelines. Subsea 7’s “Skandi Neptune” has recently finished laying the 120-kilometre long control cable from a single carousel, while the laying of the antifreeze pipes was completed this week by the Acergy-owned vessel “Seaway Falcon”. “Geofjord” and “Edda Freya” are now in full swing embedding these pipelines with the help of remote operated vehicles, while “Geosund” and “Geobay” are carrying out mapping of the seabed and verification work.
Between them, “Tertnes” and “Nordnes” from Van Oord will install over three million tonnes of stones to support the pipelines in the Ormen Lange project. They, too, are now working flat out on this task on the field.
Once the 30-inch pipelines are installed and embedded on the Ormen Lange field, Saipem will continue the work to connect all the pipelines from Nyhamna to the two subsea installations on the field, with the help of the pipelaying construction crane vessel “Normand Cutter”.
Langeled on schedule
The laying of the world’s longest subsea pipeline, Langeled, is also proceeding according to plan. In November 2005, the “LB200” finished laying the southern part of the pipeline that when complete will run all the way from Nyhamna in Norway to Easington in the UK. So far this year, the vessel has laid over 300 kilometres of the northern part of the pipeline, running from Nyhamna to Sleipner.
The southern section of Langeled will be opened for Norwegian gas exports between Sleipner and Easington in October 2006.
For Hydro and its partners, it will cost NOK 66 billion to develop the Ormen Lange field, complete with subsea installations, pipelines and the land-based processing plant. When, in October 2007, the gas stream is finally able to pass through the world’s longest subsea pipeline – from the processing plant at Aukra in the county of Møre and Romsdal, Norway, to Easington on the east coast of England – the Norwegian gas field will be able to supply British consumers with 20 per cent of their gas requirements.
The Ormen Lange/Langeled project is now 75 per cent complete, and is both on time and on budget.