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Offshore Support Journal

Offshore Support Journal

Fast craft development is literally taking off

Tue 13 Feb 2018 by David Foxwell

Fast craft development is literally taking off

In recent weeks I’ve added stories to the OSJ website about developments in fast craft suitable for use in the offshore oil and gas industry. As I noted, despite the challenging nature of the offshore vessel market, new types of fast craft continue to be developed, as even in a bad market there is a need for ships and equipment that can do a job better than existing units.

The first of the new concepts I have in mind was developed by La Rochelle, France-based Advanced Aerodynamic Vessels (A2V). The first example of the new type is due to enter service shortly servicing oil production facilities in Gabon. The vessel, Clémentine, was built for Peschaud International in France, and will be used to transport 25 oilfield technicians to inland oil production facilities. The A2V-25-CB will not operate offshore, transporting personnel on rivers along the Gabonese coast, but another, larger unit also designed by the French company is suitable for use offshore.

A2V naval architect/R&D engineer Gianluca Guelfi told OSJ the vessel has much lower fuel consumption thanks to its unique design, in which the vessel is partially lifted out of the water somewhat in the manner of a surface effect ship (SES). However, a key difference between the A2V vessel and a SES is that the latter uses blowers to produce lift, whereas the A2V concept uses aerodynamic lift to raise the vessel, in the manner of an aerofoil.

Therein lies its reduced hydrodynamic drag, and ability to reach high speeds with lower levels of fuel consumption and emissions than a conventional craft, transferring personnel over long distances in a shorter time than would otherwise be possible. Other benefits of the concept include reduced noise levels. “With A2V you get twice the speed for half the fuel. Thanks to aerodynamic support, above a critical speed, the faster A2V vessels go the less fuel they use,” said Mr Guelfi.

This critical speed depends on the application and size of the vessel but the fuel economy with respect to conventional boats is, said Mr Guelfi, “very significant” above 25 knots. This is in contrast to conventional high-speed vessels in which oversized engines allow incremental speed improvements at the cost of much higher fuel consumption and reduced payload, leading to what A2V regards as “economically and environmentally unsustainable costs per passenger.”

A larger unit than Clémentine has potential applications offshore. This is the A2V-60-CB, which is intended for long-range crew changes between shore and offshore platforms. It is capable of 60 knots in the type of conditions found offshore West Africa and could transport 60 passengers.

The A2V concept reminds me of the wind in ground effect (WIG) concept that the former Soviet Navy worked on for many years, but is subtly different. A WIG can actually take to the air because at some speeds aerodynamic lift is sufficient for it to take flight (above the water). In the A2V aerodynamic lift alleviates hydrodynamic drag but the unit remains a vessel at all times, with propellers or waterjet propulsors and diesel engines, whereas a WIG would usually use gas turbines. Its catamaran configuration provides greater lift than an equivalent WIG wing because the two hulls act like winglets (or wingtip devices) and prevent the formation of wingtip vortices. Mr Guelfi said this improves efficiency and total lift produced by the crossdeck.

In Norway, Umoe Mandal in Norway has developed a further version of its Wavecraft Voyager family, the Voyager 38 X, a high-performance crew transfer vessel for the offshore oil and gas sector. Based on technology originally developed and used by Umoe Mandal for military applications, the Wavecraft Voyager 38 X was designed to reduce transit time, enhance passenger comfort, safety and efficiency and reduce costs compared with existing designs.

The Voyager 38X makes use of proven air-cushion catamaran and SES technology combined with a sophisticated motion control system which compensates for vertical wave motion, offering comfortable transit and safe access to other vessels and installations offshore. The vessel can be fitted with a gangway and a personnel transfer system. It is designed to transport 150 passengers and a crew of six at speeds of up to 55 knots, with excellent seakeeping, even in high sea states, good fuel efficiency and reduced emissions.

Then there’s Damen’s super-slender hullform as used in the FCS 7011, which is allied to a motion compensation system and a specially designed offshore access system. This particular unit is intended to compete with helicopters in the crew transfer segment. Unlike some other designs it is not a catamaran, but a monohull with a difference as it makes use of Damen’s very slender Sea Axe hull shape, a hullform the company developed in the search for improved seakeeping characteristics for high-speed vessels.

What it was seeking – and what it achieved – in what became known as the Sea Axe was a design that could maintain high speeds in strong winds and heavy seas and provide those on board with a high level of comfort. Derived from Damen’s ‘Enlarged Ship Concept’, on which a number of highly successful Stan Patrol vessels are based, the Sea Axe took Damen’s design philosophy even further, significantly reducing resistance, fuel consumption and emissions.

The new design, the FCS 7011, is intended to provide a broad range of marine access solutions for sea states of up to 3.0 Hs. It is able to land personnel on platforms and floating production units up to a landing height of 20 m while providing a fast and comfortable crew change solution.

As I reported here, Damen said detailed cost analysis has shown that among other potential applications, the FCS 7011 is ideal for transfers in the Gulf of Mexico, Brazil, Nigeria, Cameroon and other countries offshore West Africa, along with emerging markets such as Guyana, where ExxonMobil needs to put together a logistics solution for its Liza developments. 


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