Sparks are flying in a Chinese shipyard as a new generation construction barge, called Sapura 3000, takes shape. Built by a consortium of Sembawang Shipyard and Huisman-Itrec, the new vessel is based on the Seabarge 3000 design by Sea of Solutions. The new construction vessel is expected to enter service in late 2006. It will be operated by Sapura Crest Petroleum Berhad, of Malaysia.

The new vessel is specifically designed for marine construction and pipelay operations in West Africa and Southeast Asia. Timing couldn't be better, as the offshore markets are experiencing a boom in subsea tiebacks to central production facilities. Whether production is flowing to a SPAR, a tension leg platform (TLP), a deep draft semisubmersible or a floating production storage and offloading (FPSO) vessel, often the facility is deployed as a "hub" serving several widely spread fields. Particularly in deep- and ultra deepwater, the industry has recognized that there are many more opportunities to develop clusters of small fields using a single production floater than single "elephant-sized" fields. A classic example is the huge Independence Hub project ongoing in Mississippi Canyon Block 920 in the US Gulf of Mexico, in about 8,000-ft (2,440 m) of water. Here, a centrally-located deep draft semisubmersible will accommodate production from up to 16 separate fields, each tied-back to the hub. Spotted in the center of a 50 miles (80 km) diameter circle of fields, this hub will initially drain seven fields with capacity for nine more. With subsea flowlines branching out from the hub like spokes on a wheel, efficient installation is the best way to keep costs in check while bringing the fields onstream as quickly as possible. West Africa provides similar opportunities, especially offshore Angola and Nigeria.

By focusing on potential high-activity markets, the design has been able to combine flexibility with workflow efficiency, so Sapura 3000 will be able to handle a wide variety of construction projects at maximum cost-effectiveness. While its principle role is pipelaying and offshore construction, the design can be enhanced to support suction-piling upending operations as well as saturation diving. In addition, although initially equipped for S-lay over a stern-mounted stinger, the barge can be easily configured for J-lay operations as are used in very deep waters. In anticipation of pipelay operations involving longer joints, the welding stations and pipehandling units can be extended to handle joints up to 60-ft (18.3 m) in length. A class 2 DP system supports station-keeping and barge alignment during operations.

At the heart of the design is a centerline located firing line with 6 welding stations, non destructive testing (NDT) station, corrosion and blasting station and a doping station. By locating the firing line along the centerline of the vessel any vertical motion component due to vessel roll is eliminated. The maximum pipe diameter that can be accommodated is 60-in. (1.5 m) at tensions up to 180 tons, enabled by three 60-ton tensioners. If required, a fourth 60-ton tensioner can be added. Special pipehanding cranes mounted on both port and starboard sides load and rack pipe. Offloading of pipe joints from supply vessels that can be tied-off alongside on either side of the Sapura 3000 can be accomplished without interrupting pipelay operations.

Providing both versatility and high-capacity in support of all construction projects is the stern-mounted revolving crane, provided by Huisman-Itrec, BV. With a rated capacity of 2,200 short-tons (1,996 tonnes) at 102-ft (31 m) radius fully revolving, the crane can accommodate big lifts. Of the "kingpost" design, the crane's slim profile enables it to handle loads in the water very close to the barge's hull, in fact, when rigged up over the stern the crane can handle up to 3,000 short-tons (2,721 tonnes) at 88-ft (27 m) distance from the stern.

Measuring up to the task

Sapura 3000 has accommodations for up to 330 workers housed in 10 single-person, 50 two-person and 55 four-person cabins. In addition, suitable dayrooms and offices are provided onboard. A helideck can accommodate a Sikorsky S61-N or Super Puma helicopter.

Purpose-built design

Often, marine construction and pipelay vessels are conversions, or adaptations of existing ships or previous designs. However, in developing the Seabarge 3000 concept, the designers started with a clean slate-every aspect of the vessel's design complements its intended role. "Realistically, that's the only way to optimize workflow efficiency and safety," commented Sea of Solutions' Commercial Director, Bob Rietveldt. "We combined the best of marine engineering and oilfield construction experience in the barge's design." The tween deck designed for the pipe firing line, and the main deck for construction work and pipe joint storage ensures a highly flexible design for either pipelay or heavy lift operations. For example, as much as 530,000 ft3 (15,000 m3) of ballast water can be repositioned within the hull tanks to maintain vessel stability during heavy lifts. The forward deck house keeps crew accommodations as far away from the work stations as possible so workers can get proper rest between shifts. Even the fact that pipehanding cranes are available on both sides of the vessel allows resupply operations to be staged on the sheltered, or lee, side of the barge. And the multiple azimuthal thrusters provide maximum maneuvering ability, particularly when working close by other vessels or structures.

As the oil and gas industry increases the percentage of production coming from offshore fields, the world's maritime and marine construction industries are keeping pace by introducing vessels such as Sapura 3000.

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