Artist's concept of Statoil's Swath unit. Illustration by Gunnar Flusund, courtesy of Statoil.Norway's Den norske stats oljeselskap AS aims to halve drilling and well operating costs in development of Aasgard fields in the Norwegian Sea by using an innovative twin hull drilling vessel.
The small waterplane area twin hull (Swath) ship concept was developed by naval architects Kverndokk & Eldoey of Aalesund, Norway. It is based on a catamaran hull first designed in the 1940s.
Statoil plans to use a Swath vessel for drilling and well operations in water depths to 1,500 m. The company said the first Swath unit could be operational in late 1997.
Statoil operates the Aasgard fields, under development using an oil production ship and gas production semisubmersible (OGJ, Oct. 9, 1995, p. 32).
"Swath would replace conventional drilling rigs for such work," Statoil said. "A North Sea semisubmersible currently costs around 1.2 million kroner ($190,000)/day. The aim is to cut this figure by up to 50%."
The company reckons using the Swath ship will trim 500 million kroner ($80 million) from Aasgard development costs.
The design is said to have similar stability, seakeeping, and load handling characteristics of a semisubmersible rig and to be comparable to a fourth generation rig.
Model testing was completed in January at the Danish Marine Institute in Copenhagen. A full sized unit would be 122 m long with a 2,600 sq m deck space and weigh 10,000 dwt. Sailing speed would be 13-14 knots.
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