As the 1,224 km Nord Stream Pipeline nears completion and prepares to transport gas through its second line, Pipelines International pays tribute the Langeled Pipeline by looking at what went into the construction of what was once the longest subsea pipeline in the world.
Between 2003 and 2007, a dedicated large diameter export pipeline called the Langeled was installed to transport dry gas from Nyhamna to the east coast of England in order to supply gas to the United Kingdom as part of the Ormen Lange gas development project.
The Ormen Lange Field, discovered in 1997, is located 120 km off the northwest coast of Norway in water depths of between 800 and 1,100 m. The field is the second largest gas field in on the Norwegian Continental Shelf, with recoverable gas estimated at 397 Bcm.
At the time of its construction, the Langeled development project was managed by Statoil on behalf of Hydro. As of 1 September 2006, Gassco took over the operatorship of Langeled.
The Langeled is a 1,200 km gas pipeline that extends from Nyhamna on the west coast of Norway to Easington on the east coast of England, and which is tied into the Sleipner Gas Field approximately halfway across the North Sea. The northern half of the pipeline consists of a 42 inch diameter, 250/215 bar pipeline, whilst the southern half from Sleipner to the UK comprises a 44 inch diameter, 157 bar pipeline.
Gassco Project Manager Leif Solberg, who was formerly employed by Statoil as the Langeled Project Manager, said that the sheer size of the pipeline project made it a unique project to work on – not only in terms of length, but also in diameter.
“The pipelay barge needed to be upgraded to be able to lay 44 inch diameter pipe, and the 1,200 km length of the pipeline required pigging over long distance,” he said.
The pipeline project began in 2003, with pipelay taking place in 2005 and 2006. The project was engineered by Snamproggetti, with Acergy and Allseas contracted for pipelay, and Subsea Seven and Technip undertaking the tie-in work.
At peak, approximately 4,000-5,000 workers were employed for the project, with a total of 70-80 vessels involved, including three laybarges.
Mr Solberg said “There were 25 different nationalities represented on the laybarges. We focused on good co-operation and introduced a common goal in health, safety and environment (HSE) throughout the construction work, which resulted in good and efficient team work.”
Mr Solberg said that regular meetings with stakeholders were held throughout the entire project period.
“We maintained an open atmosphere to relay the challenges we experienced and the actions taken to solve them.”
Safety for personnel at all levels was a major focus from day one, with particular attention paid towards lifting, coating, marine and diving operations.
Mr Solberg said “The Langeled HSE programme spelled out some ground rules for the work, such as to always work closely with the contractors, and be proactive. Employees were encouraged to work with the long-term goal in mind, but to focus on action plans up to six months ahead. Both Statoil and the contractors were also required to use visible and hands-on leadership.”
Mr Solberg also outlined some of the other challenges faced during construction. “The connection to Sleipner, in order to supply gas from Sleipner and Troll, was a challenge. So, too, were the landfall in Easington, which required a 380 m tunnel from 7 m below sea level, as well as all the diving work.
“We also had to execute a crossing at the Norwegion trench in around 300 m-deep water, with a riser tie-in at the Sleipner riser platform and a landfall at Easington, and had a number of subsea tie-ins, with eleven hyperbaric welds that required 900 dives and approximately 6,000 man hours in saturation.”
The commissioning of the 44 inch diameter southern part of the Langeled was completed in 2006, along with the Easington receiving facility and the tie-in at Sleipner; the pipeline was delivering gas from the Sleipner and Troll fields by October 2006. The 42 inch diameter northern section of the pipeline was completed and in operational by 2007.
The pipeline is still in operation today, providing a versatile transport solution with gas deliveries to Britain as well as continental Europe via the Sleipner riser platform and Gassled’s existing transport network.