OSD has secured a design contract for two IMT965 seismic support vessels with a bollard pull in excess of 50 tonnes for China Oilfield Services (COSL), Beijing.
The 64.9-metre x 16-metre x 5.65-metre vessels will be used to provide a range of support activities to larger seismic vessels which operate continuously for months when conducting seismic surveys.
Designed to have a multi-role capability in support of the mother ship, the 1,800DWT vessels can be used for re-fuelling, fresh water replenishment, the provision of refrigerated stores and dry provisions, the supply of spares and general stores, emergency towing, and escort support and guard duties.
The IMT965 carries 980m3 of cargo oil for refuelling the mother ship, either alongside or ahead.
"Seismic vessels tow multiple streamer arrays at a speed of around five knots. In the event of an engine failure on the mother ship," commented OSD.
"It is important to ensure that the streamers do not sink and become damaged on the seabed. Should this occur, the support vessel provides emergency towing within a target time of five minutes from the occurrence of engine failure to the point of taking up the tow."
The operating cycle for the IMT965 requires it to be on station shadowing the mother ship for prolonged periods. During this time the IMT965's activities include keeping passing vessels clear of the streamer arrays, and ensuring that there is a traffic-free area ahead of the mother ship. The vessel is classed with a DP-1 notation that will allow it to shadow the mother ship at a pre-set distance for long periods.
The main IMT 965 propulsion arrangement is a hybrid system, comprising twin controllable-pitch propellers, each driven by a medium-speed diesel engine. A PTO/PTI alternator/motor is connected to each main gearbox, and two 360kWe diesel generators are also provided. The system is arranged so that one engine can drive both propellers for maximum fuel economy and redundancy.
The IMT965 has accommodation for a total of 48 persons, including cabins for mother ship relief personnel.
The operating cycle of the ship is based on 45 days divided into activities including slow steaming, alongside/ahead refueling of the mother ship, emergency tow, emergency sprint, steaming to/from shore and alongside in port.
