STAVANGER, Norway – At the beginning of the year, Island Offshore, with its partner Baker Hughes, entered a back-to-back agreement with VTT Maritime, which had been awarded a contract for ground core sampling above the world’s longest [25,5 km (16 mi)] and deepest [385 m (1,263 ft)] subsea road tunnel, named Rogfast.
Together with the end client, Statens Vegvesen, (Norwegian Public Roads Administration), it was decided that Island Offshore’s new coiled tubing drilling method should be applied. Subsequently, Island Offshore has begun its application of coiled tubing drilling technology in Boknafjorden, north of Stavanger, Norway, utilizing a monohull vessel.
This system can construct high angles in the well over a very short distance [up to 15 degrees over 30-m (98-ft) drilled hole]. To avoid a full marine riser spread, Island Offshore developed a subsea injector. A second injector has also been installed onboard the vessel in order to keep the coiled tubing between the subsea injector and the vessel in tension.
The work is being undertaken by Island Performer, Island Offshore’s newest vessel. A total of approximately 440 m (1,444 ft) of core samples will be taken from four individual locations in order to obtain detailed information about the geological conditions of the tunnel route, with water depths ranging from 200 to 300 m (656 to 984 ft).
Island Offshore says that this is the first time an open coiled tubing system has been used in a drilling operation offshore. New equipment and procedures have been developed to introduce a reliable and functional system.