On August 21, the Polarled gas pipeline crossed 66 degrees and 33 minutes north of the equator becoming the first pipeline to cross the Arctic Circle.
The 482-kilometre long and 36-inch wide pipeline will run from Nyhamna in western Norway to the Aasta Hansteen field located 300 km from land in the Norwegian Sea.
Polarled will also be the deepest pipeline on the Norwegian continental shelf as the Aasta Hansteen field lies in water depths of 1,260 meters. Furthermore, it will be the first time a 36-inch wide pipe is laid in such deep waters anywhere in the world.
The Aasta Hansteen discovery was made in 1997 and the field is operated by Statoil. Together with Haklang and Snefrid Sør, the recoverable resources are estimated at 47 billion cubic meters of gas.
The world’s largest pipelaying vessel, Solitaire, from Allseas, is carrying out the pipelay job and is advancing slowly, exactly 24.4 meters at a time, every sixth minute or so, around the clock.
Pipelay Operations
The vessel will arrive at the Aasta Hansteen field in September, if weather permits. Even early in the autumn high waves and strong wind leading to interruptions must be expected, however, the weather has been good for a long period now.
“We are progressing well at the moment, conditions have been good for more than 50 days in a row, and at the end of July we set a record of laying 4.8 kilometers of pipes in one day,” says Kenneth Aksel Kristensen, one of Statoil’s company representatives on board the vessel. The vessel needs a constant supply of pipes. Every pipe is 12.2 meters long, and the vessel is laying around four kilometers of pipes a day. This means that it needs a supply of more than 300 pipes a day, filling two to three boats every day. Two cranes are lifting the 12-15-tonne pipes on board, and when one boat is empty it only takes a few hours before the next of six shuttle boats arrives with more pipes.
“The pipes arrive from Wasco in the city of Mo i Rana, where they are coated. This means that they have been given a concrete layer to protect them from trawling and make them heavier,” explains Kristensen. When a pipe is lifted on board the 376-meter Solitaire it enters a huge assembly line. The pipe is sent from station to station where specialized operators are welding and checking the pipe before it becomes part of the long tail behind the Solitaire.
The Solitaire crew is working around the clock. It takes around 90 minutes from when a pipe is lifted on board and enters production until it has become part of the ever-extending Polarled pipeline. There are 410 people on board the vessel, including two asset owner representatives from Statoil and eight people from DNV GL – who are also part of the day and night operation. The pipeline is not laid in a straight line: “We have examined the seabed thoroughly in advance to find the best route and also to avoid corals and large rocks,” says Arne Fosse, Statoil’s head of the Polarled construction
At start-up, the gas from Aasta Hansteen will be the only gas passing through Polarled, but the pipeline has a diameter of 36 inches and capacity for more gas: “We have therefore installed six connection points, call it future slip roads to the new gas highway,” says Håkon Ivarjord, Statoil’s project venture manager for the Polarled development project. “Polarled will open up for gas export to Europe from a completely new gas province, and with the infrastructure in place it will also be more attractive to explore the surrounding area.”
