Superduplex pipes for the Knarr project

A long time ago, “Knarr” was a type of ship on which the Vikings transported their trading goods across the seas. Today the oil and gas industry use the name to refer to a field in the North Sea: From 2014, oil and gas reserves are to be extracted there by BG. For this project, BUTTING is supplying Subsea 7 with pipes which will be used in bundle technology.

In the Knarr field, 120 km west of the Norwegian coast, there are large oil and gas reserves. Extracting these resources is difficult, because they are underneath the bottom of the North Sea. BG has contracted Subsea 7 to deliver a bundle solution for the development of the Knarr field. The bundle will be installed in 410 m of water depth and will include flowlines for water injection, production and service as well as control tubing and electrical cables. The production flowlines will transport the extracted oil and gas from the subsea wells to a ship (FPSO) for processing, storage and offloading.

For the production pipeline, BUTTING is manufacturing superduplex UNS S32760 pipes with an outer diameter of 219.1 mm and wall thicknesses of 15.9 mm and 20.6 mm. Just under 10 km of pipes are being produced in standard lengths of up to 12.2 m without circumferential welds.

BUTTING will deliver the pipes to Wick in Scotland in a total of four batches by June 2013. Still on dry land, pipe joints will be welded together to form a single 4.3 km long pipeline bundle. The actual installation will be done by pulling the bundle out to sea and towing it the 540km from Wick in the North East of Scotland to the Knarr field in Norway. There, at the final destination, the bundle will be lowered to the bottom of the sea and prepared for 20 years of operation.

BUTTING – Progress by Tradition