Deepwater surge galvanizes DP power sector

The top module of the Aquamaster USE 3001 thruster system for the upgraded DP pipelayer Hercules. D eepwater drilling successes in the Gulf of Mexico have triggered a spate of activity in the construction and conversion sector. New rigs, drillships and pipelay barges are being produced, equipped with dynamic positioning systems to counter the harsher environments of these deeper offshore plays.

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Two of these 2.2MW Comtaz propulsion units were delivered last year to the newbuild platform supply vessel Skandi Marstein.


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The top module of the Aquamaster USE 3001 thruster system for the upgraded DP pipelayer Hercules.


D eepwater drilling successes in the Gulf of Mexico have triggered a spate of activity in the construction and conversion sector. New rigs, drillships and pipelay barges are being produced, equipped with dynamic positioning systems to counter the harsher environments of these deeper offshore plays.

The extra power demands involved have benefited propulsion/thruster specialist Kamewa Group and its subsidiary in south-west Finland, Aquamaster-Rauma. Major orders have been secured for two newbuild drilling units, both designed to operate in waters up to 3,000 metres deep.

Discoverer Enterprise is a semisubmersible contracted to Sonat Offshore Drilling. The hull and key marine systems are being built by Astano in northern Spain, with propulsion and thrust for dynamic positioning being generated by six Aquamaster UUS 7001 units outputting 30MW in total. Conoco/Reading & Bates' new drillship, measuring 220m long and 43m broad, is under construction at Samsung's site in Korea. Here six underwater demountable Aquamaster UUS 60001 azimuthing thrusters, fitted with Kamewa tilted nozzles, will output 24MW combined.

Ocean Clipper, owned by Diamond Offshore, is a drillship undergoing conversion at Atlantic Marine in Mobile, Alabama. The vessel is being fitted with an upgraded positioning system based on Kamewa products, including a single top-side demountable Aquamaster USL 3001 azimuth thruster as well as five Kamewa TT 2400 fixed-pitch tunnel thrusters to aid DP capability and deepwater operation. A special locking device will allow mounting and demounting of the thrusters even out at sea.

Finally, Global Industries, Lafayette is converting its derrick barge Hercules at the same site in Mobile to a DP pipelayer. Following the conversion, the barge will be able to handle pipelines up to 1.2m in diameter. The DP system will employ six Aquamaster USE 3001 azimuth thrusters.

Comtaz

Independently of Kamewa, which it joined in 1995, Aquamaster-Rauma has progressed development of a new generation of azimuthing thrusters at its headquarters in Rauma, Finland. These are fitted with contra-rotating propellers, a technique claimed to increase propeller efficiency while subduing noise and vibration. The Comtaz propulsion units feature a stream-lined body form, designed to achieve higher speeds than traditional thrusters.

Aquamaster's first new generation Comtaz units were delivered last year to the Skandi Marstein, a new platform supply vessel managed by District Offshore, Bergen and under long-term contract to Shell. The vessel, built by Brattvaag Skipsvert to a Marinteknikk design, is suitable for transporting pipes, cement, dry and liquid cargoes to and from drilling rigs and other vessels.

Skandi Marstein was designed to achieve superior operating economy, reliability, ease of maintenance, maneuverability, minimal pollution and interior flexibility. These aims are assisted by the diesel-electric power plant, powered by four 1.47MW diesel engines. Twin Comtaz 25 propulsion units in the stern are each driven by a 2.2MW electric motor with 100% variable rpm.

Aquamaster also supplied a retractable UL 1201 unit, driven by an 880kW motor, and a full set of Rauma winches for mooring, anchor and tug duties. Kamewa provided a 735kW tunnel thruster.

Yet another advanced vessel reference is SubSea Offshore's newly built ROV and survey support ship Kommandor SubSea 200, taken last year on long-term charter from owner Hays Ships. The vessel, which is working in the North Sea, was built by North Sea Shipyard of Ringkobing to Norwegian Maritime Directorate standards for unrestricted operation around offshore installations.

The 78 meter long, 1,000 ton dwt vessel can achieve a speed of 14 knots with allegedly exceptional maneuvering and control capability. Main propulsion is based on two Aquamaster US 1701 units mounted aft, each driven by a 1.3MW electric motor. At the front are two conventional tunnel thrusters and a retractable, electrically driven Aquamaster UL 1601 unit. All thrusters can be connected into the fully redundant DP system.

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