October 14, 2005
Aker Yards to build well intervention vessel
Norway's Island Offshore, in which Edison Chouest Offshore is a partner, has signed another contract with Aker Yards.
Worth approximately NOK 650 million (almost US $100 million), it covers construction of a Well Intervention Vessel for delivery in January 2008.
Built to a new Rolls-Royce design (UT 767 CD), the vessel will be maintain and repair oil and gas wells in depths down to 600 meters.
It will operate with a riserless wireline intervention system. and will deploy an ROV, (remote operated vehicle), for operations on the sea bed. The sub sea related equipment will be provided by FMC and Aker Kvaerner Wellservice.
Island Offshore has been assigned 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, built by Aker Yards, in 2006 and 2007. The new vessel, to be named Island Wellserver,will take over the service from April 2008.
Intervention services envisaged include production logging, plugging and gauging operations, perforation and re-perforation and downhole mechanical work. The vessel will also carry out ROV operations.
Working on live wells means that the ship has to comply with very strict regulations.
It 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 4 m or 6 m significant wave heights, to launch and retrieve ROVs in up to 4 m 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, UT-Design has developed a 116 m long, 25 m beam, 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 containerized 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. The oil related equipment will be provided by Kongsberg and FMC.
A dynamic positioning requirement corresponding to IMO DP3 has a major impact on the propulsion system.
Island Offshore has specified a diesel electric system with azimuth thrusters for main propulsion.
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 maneuvering forces, backed up by two Supersilent tunnel thrusters, and a swing-up azimuth thruster under the bow that 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 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.