PRODUCTION • PROCESSING • HANDLING
Nexans is a leading player in cable technology. The company is present at every level of oil and gas production, providing a wide range of power and telecommunication cables and umbilicals for offshore exploration, production, processing, storage and transport
THERMOPLASTIC HOSES AND STEEL TUBE UMBILICALS Originally, only thermoplastic hoses were used to carry fluids. But in some kinds of service they have specific weaknesses – for example, they can deteriorate when exposed to some types of chemical, have a limited pressure capability and can be subject to collapse when used in deep waters. In the early 1990s, therefore, Nexans pioneered the alternative use of super duplex steel tube that eliminates the potential performance problems that might be encountered with thermoplastic hoses by offering good corrosion resistance and chemical compatibility with most chemicals, as well as good collapse resistance and a high strength-to-weight ratio. Some customers specify other tube materials, for example zinc-clad, seam- welded high-strength, low-alloy steel. Nexans umbilicals and submarine
power cables are manufactured at the firm’s purpose-built Halden factory in Norway, which offers a totally integrated operation from engineering and steel tube welding to qualification, termination and testing. It can manufacture laid-up umbilicals with diameters of more than 250mm and to date has supplied well over 1,800km of umbilicals. A special capability offered by Halden is the application of layers of steel armour for
additional protection or to add weight. After passing through the armouring machine the next stage in the process is either the extrusion of an outer polyethylene sheath or application of a polypropylene wrapping with bitumen added as part of the yarn to provide good corrosion protection. All the termination work and factory acceptance testing is performed at the factory. Te finished umbilical is stored on one
of a variety of turntables. From here it is transferred directly to the cable vessel docked at the factory’s deep-water quay. A good example of umbilicals in action
is the West Nile Delta Taurus Libra project in Egypt where Nexans delivered 48km of static umbilicals to BP and partner DEA. Te umbilicals consisted of electrical and fibre optic cables as well as hydraulic and chemical lines. BP’s Shaz Deniz field in Azerbaijan also uses umbilicals supplied by Nexans. For the next stage of the project, BP Exploration (Delta) has ordered 100km of static umbilicals and associated accessories. Tis will help BP and partner DEA develop the Giza, Fayoum and Raven gas condensate fields. Umbilicals also play a key role in the Greater Enfield development, off the coast of Exmouth, Western Australia. Te project, worth around €20 million, will be Nexans’ first to be installed in Australia.
UMBILICAL ENGINEERING T
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SUBMARINE POWER CABLES AND INSTALLATION Te market for submarine power cables is currently very active and Nexans serves this market with turnkey and supply contracts. For installing submarine power cables, Nexans is the owner and operator of the C/S Nexans Skagerrak – one of the world’s most advanced cable-laying vessels, with a next-gen global positioning system and multiple cranes. Not only is it equipped with a 7000 tonne capacity turntable but it also has the ability to repair submarine power cables. Skagerrak provides a platform for Capjet – an in-house trenching system developed for trenching umbilicals, power cables and fibre-optic cables as well as pipelines based on the water jetting principle. Te water jet system is used to create the trench and to propel the trenching machine. It is based on Newton’s third law of motion – every action has an equal and opposite reaction. Te propulsive force or thrust from the reaction that is created when the stream of water is forced
Cables about to be transported to Shaz Deniz from the Halden plant in Norway
here are no off-the-shelf umbilicals. They must be custom designed to meet specific customer needs using a structured approach and strict methodology, together with clearly defined design rules. Nexans is
able to draw on an extensive database derived from many years of umbilical and component qualification testing and field experience. It has also developed Uflex, a finite-element based nonlinear stress analysis tool, to increase understanding of the behaviour of umbilicals as exploration moves into even deeper waters, approaching 4,000m. l
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