Construction costs will depend on the type of fields to be developed, but Aker claims a Buoyform platform could be built in 23 months, for 500 million kroner ($70 million) less than a comparable semisubmersible or production ship.
Buoyform consists of a moored subsea conical storage tank, on which is mounted a deck carrying a drilling rig, processing equipment, and quarters.
With an 83 m diameter and 400 m draft, the Buoyform has smaller and calmer motions than either a production ship or semisubmersible, claims Aker.
Norway's Den norske stats oljeselskap AS (Statoil) has helped in concept development. Jon Erik Reinhardsen, executive vice-president, Aker Maritime, told OGJ that Statoil has Buoyform in mind for a number of finds.
"There are more than 100 discoveries off Norway that are too small for development with existing technologies," said Reinhardsen. "Statoil is interested in having one unit deplete many fields."
Statoil and Aker have been evaluating Buoyform units with production capacity of 60,000 b/d of oil and storage capacity of 570,000 bbl. They have proposed building the hulls at Aker's Mantyluoto yard in Finland.
Aker feels the ideal operating depth range for Buoyform is 70-400 m. Below 70 m, mooring would be difficult, while deeper than 400 m it could still be applicable, but other concepts such as spar platforms may be better suited.
Reinhardsen said a typical Buoyform unit for small field depletion could have production capacity of about 20,000-40,000 b/d range, suitable for producing from one to five wells.
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