The 53 m vessels will have a fuel efficient hybrid propulsion system delivering a flexible economic solution for the varied conditions required to support seismic survey vessels including transit speed, slow speed escort and support work and a high degree of manoeuvrability.
Neil Patterson, managing director of OSD-IMT, the UK arm of Offshore Ship Designers says, “We worked closely with Grandweld during the tender period and following their selection as one of the short-listed bidders, we assisted them technically during the successful contract negotiation process, and are pleased to have been entrusted with the design of these new vessels.”
The vessels will be chartered by Bourbon to CGGVeritas with delivery of the first vessels set for the end of 2012. They will be used to support the fleet of CGGVeritas seismic survey vessels operating all over the world, providing them with services including crew change, fuel delivery, storage, assistance and support during at-sea maintenance operations.
Operational requirements of the design include:
• Cargo runs from port to the mother ship
• Transfer of fuel, potable water, dry and refrigerated stores and general cargo to the mother ship.
• Transfer of crew to and from the mother ship.
• Accompanying the mother ship when conducting seismic operations
• Towing of the mother ship when conducting seismic operations
• Retrieval of streamer cables
Key feature of the hybrid propulsion system are:
• Two main marine diesel propulsion engines, two controllable pitch propellers in nozzles, two main gearboxes each with a PTI electric propulsion motor and three diesel driven generating sets, and two electrically driven bow tunnel thrusters.
• Diesel-mechanical mode using main engines only used for the transit operation.
• Diesel-electrical mode with main engines declutched using PTI propulsion motors powered by the gensets for chase and slow speed operation.
• Boost mode with main engines and PTI propulsion motors (powered by the gensets) engaged used for towing operation.
• Automatic push button selection between the different propulsion modes.
Service speed in transit mode with only main engines in operation – 11.0 knots
Service speed in diesel-electric mode without main engines – up to 6.0 knots
Service speed in boost mode with main engines and PTI motors – 11.3 knots
Bollard pull in boost mode with main engines and PTI motors – 50 tonnes
Main particulars are length 53.8 m, beam 13.0 m, depth 5.8 m, load draft 4.8 m, cargo fuel capacity 850 cu m, marine gas oil fuel 260 cu m, potable water 100cu m, refrigerated and dry storage capability as well as space on deck for stowage of stores containers.