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    Aker Yards to build well intervention vessel for Island Offshore

    Vessel & ROV News // October 14, 2005

    Island Wellservicer is being built to a very high specification.

    Island Frontier will act as front-runner for Island Wellservicer.

    Aker Yards has signed a contract worth approximately NKr 650 million (circa US$100 million) to build a well intervention vessel for Island Offshore in Norway.

    The vessel will be delivered in January 2008.

    The main duties for the new vessel, which will be a Rolls Royce design, will be maintenance and repair of oil/gas wells in waters of up to 600m, operating with a riserless wireline intervention system.

    The vessel will operate a ROV for operations on the sea bed. The subsea related equipment will be provided by FMC and Aker Kvaerner Wellservice.
    Island Offshore has been awarded a contract by Statoil for well intervention services on the Norwegian continental shelf. Under the contract Island Offshore will use its pioneering light well intervention vessel Island Frontier, which was also built by Aker Yards, as front-runner for the contract in 2006-07.

    The new vessel, to be named Island Wellserver, is a new Rolls-Royce design (designated UT767CD), and will take over from Island Frontier from April 2008. 

    The UT767CD Subsea Riserless Well Intervention Vessel will be delivered by Aker Yards' Langsten shipyard, and will be 116m long with a breadth of 25m. it will have diesel electric propulsion based on four main generator sets with a single auxilary generator set, providing a total of approximately 13,000kW.

    Fitted with electrically driven azimuthing main propellers each of 3,500kW, the new vessel will bear the class notation DNV, Dynpos AUTRO, Comfort (1), Clean Design, and a deadweight of 8,200 tons.

    Intervention services envisaged include production logging, plugging and gauging operations, perforation and re-perforation and downhole mechanical work. Working on live wells means that the ship has to comply with very strict regulations and will be built to the Ship-Shaped Well Intervention Unit class rules of DNV with dynamic positioning to DYNPOS-AUTRO standard. Island Offshore is also specifying Clean Design class and Comfort V(1)C(1) class.

    Depending on the type of interventions, the vessel has to be able to carry them out in up to 4m or 6m significant wave heights, to launch and retrieve ROVs in up to 4m significant wave height, and to stay on location itself in standby mode in environmental conditions corresponding to Beaufort 9 prior to disconnecting from the well.
    To meet this difficult brief, Rolls-Royce UT-Design has developed a vessel with a large freeboard to give the required stability, low motions and freedom from spray and green water on deck.

    The deck will be dominated by the module handling tower and a large working deck area has been specified so that containerised tanks and equipment can be carried.

    A large crane will be installed to give heavy sub sea lifting capability and there will be an area of low freeboard aft to facilitate lifting equipment over the stern. Two Oceaneering ROVs will be carried in hangars, one either side of the vessel.

    A dynamic positioning requirement corresponding to IMO DP3 has a major impact on the propulsion system. Electrical power will be generated by four Bergen gensets of  two different sizes to give maximum operating flexibility.

    Two Ulstein Aquamaster Azipull thrusters with pulling propellers will provide the main propulsion and manoeuvring forces, backed up by two Supersilent tunnel thrusters, and a swing-up azimuth thruster under the bow which will be powered by its own independent diesel engine.

    One result of the extremely stiff regulations applied by the Norwegian Petroleum Department to this type of vessel is that two freefall lifeboats have to be provided on each side of the vessel. The need to get adequate launching height for these heavy craft imposes severe stability criteria on the mother ship.

    Well intervention and ROV operations also imply a much larger crew than is necessary for navigating the ship so accommodation will be provided for 95 people in single staterooms.

    Island Frontier achieved very low noise levels and Island Wellserver is designed to be even quieter, while its Clean Design notation stipulates a minimum impact on the environment.


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