Inocean has developed a steel production riser for deepwater application in a joint industry project sponsored by Norsk Hydro and Statoil. According to partner Jon Erik Borgen, the L-riser overcomes both the limitations of weight and fatigue life associated with vertical steel risers in deep waters and the limitations of diameter and pressure capacity associated with deepwater flexible risers.
The L-riser is a variation of a simple catenary riser but in an L-shaped configuration. The upper section, which is hung-off in normal fashion from the floating production unit at the surface, is slightly offset from the vertical. Near the seabed the riser turns through a 90º corner bend such that the lower section lands on the seabed directly below the platform. The corner bend is supported by a mooring system. Inocean holds the L-riser IP patent.
In the JIP sponsored by Norsk Hydro and Statoil, the L-riser was qualified at design concept level. It was established that the concept, which can be deployed in waters down to 3,000 m, has an acceptable fatigue life in extreme conditions and can accommodate large motions and offsets of the floater.
Inocean's L-riser concept is a steel production riser for deepwater applications.
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The project studied a 28-in. gas export riser deployed from a semisubmersible platform located in a typical harsh environment area, one of the development solutions that might have been applicable to Hydro's Ormen Lange development in the Norwegian Sea.
Further development is now taking place under the auspices of the Norwegian Deep-water Program, in which the sponsors are BP, ChevronTexaco, ConocoPhillips, ExxonMobil, RWE-Dea, Shell, and Total, in addition to Hydro and Statoil. The aim is to qualify the concept for the Norwegian Sea environment at water depths of 850-1,750 m.
Inocean provides specialist engineering services in the design and development of floating structures and mooring and riser systems. Recent and current work includes analysis of the riser and mooring systems for Statoil's Kristin floater, on behalf of Technip Offshore Norge and Aker Kværner, analysis related to the hull and process module foundations for Bergesen's Sendje Berge and Sendje Ceiba FPSO conversions, and hull structure analysis for the Fred.Olsen operated Jahre Viking, the world's largest tanker, which is being converted to an FSO.
