Multipurpose shuttle embarks on second production role

Production, storage, or drilling options for floater

Nick Terdre
Contributing Editor

Multipurpose shuttle tanker Berge Hugin on arrival at Aker McNulty in February, where it is being converted to a production ship. [15,390 bytes]

This fall, first oil will flow from Enterprise's Pierce field in the North Sea, through the Berge Hugin production ship. The event will fulfill Navion's ambition to become involved in North Sea oil production.

The Norwegian company, owned jointly by Statoil and shipping group Rasmussen, made its debut in the production arena late last year, when the Navion Munin production ship received first oil from the Lufeng 22-1 Field off China.

Both these production ships have been built to Navion's multipurpose shuttle tanker (MST) design. In addition to production, they can also be used as floating storage vessels or converted to drillships.

When no work is available in these functions, the MST can be allocated work in crude transport - as a major long-haul operator and the world's leading shuttle tanker operator. Hence, the MST concept contains a flexibility which considerably enhances the vessel's chances of employment.

So far, the philosophy is chiming well with reality. In addition to the two MSTs contracted as production ships, two more are under construction, both of which, on the back of long-term contracts, are being converted to deepwater drillships.

Berge Hugin is a good example of the MST's operational flexibility. In its short life - it was delivered in early 1997 - it has already worked as a long-haul tanker, as a shuttle tanker in the North Sea, and as a storage vessel for Statoil's extended well test of the Connemara Field off southwest Ireland.

Production vessel

The MST as production ship is aimed particularly at fields remote from infrastructure and with marginal reserves, according to Allan Millmaker, Navion's senior vice president for floating production systems. In rough terms this means fields which contain 100 million bbl of oil or less, and are located some 50 km or more from infrastructure. Above this reserves level, the attractions of a field-specific production ship or floater grow. Below this distance, the attractions of alternative concepts such as subsea facilities grow.

Millmaker is also keen to stress the contribution made by leasing to the notion of flexibility. Lufeng is a good case in point, being a marginal field for which previous attempts to find an economic form of development had failed. Here, Navion's vessel has been leased for a firm period of only two years, with options for a further five years. In the case of Pierce, an economically more robust development, the lease is for a firm period of five years, extendible to 13.

By offering a leasing arrangement tailored to the uncertainties in expected field life, Navion is sharing some of the reservoir risk which traditionally falls on the field owners' shoulders. And by spreading the risk, it helps to bring uneconomic reserves within the bounds of economic development. This benefit is perhaps not yet fully appreciated by prospective oil company customers, says Millmaker.

The leasing concept also covers the provision of the process equipment. Here, Navion has a cooperation agreement with Advanced Production Systems (APS), a company jointly owned by Statoil and Aker Maritime. APS designs and supplies field specific equipment for each application.

For the Lufeng vessel, which will have a short production plateau of 60,000 b/d, the topsides equipment was fabricated and installed at the Jurong yard in Singapore. In the case of the Pierce ship, for which plateau production will be some 45,000 b/d, it is the Aker McNulty yard on Tyneside which is performing this role.

The leasing concept also leads on naturally to an operations role for Navion. For the Pierce contract, the company will be the duty holder for the vessel, providing the marine operations crew and onshore support and logistics, while APS will provide the production and maintenance crews. Under a separate contract, Navion shuttle tankers will ship the produced oil to market.

Once production comes to an end, the vessel and the equipment return to their respective owners, ready to be redeployed at a new location. The risk in finding future employment lies with Navion and APS.

Lufeng, Pierce

The Lufeng and Pierce MSTs are 103,000 dwt vessels with 640,000 bbl storage. They have an overall length of 253 meters, a breadth of 42 meters, and a draft of 23 meters.

An integral part of the vessel design is the submerged turret production (STP) system, itself a further development of the submerged turret loading (STL) system which has significantly improved uptime for offshore loading operations in adverse weather conditions.

The STP consists of the buoy and mooring lines, on the one hand, and a rotating connector, developed by Framo Engineering, which is built into the ship. In the case of impending bad weather, the two can be easily disconnected, in which case the buoy is left to float some 45 meters beneath the surface until the bad weather has passed and reconnection can be made.

With two important references under its belt, Navion is optimistic that it can win further production ship contracts. However, with no MSTs available to offer for new contracts, the company is offering Vinga, a tanker equipped with an STL system and currently working in the trading market.

This ship is a candidate for Fina's Otter marginal field development in the UK sector. Navion also has an interest in Smedvig's SPU 550, a newbuild Tentech vessel recently delivered in Japan.