At Ormen Lange there is no production platform on the surface. The turbulent waters covering the oil and gas field off the Norwegian coast reveal nothing of the innovative production system working on the sea floor working deep below, piping oil and gas directly to a processing plant onshore at Nyhamna.
“This unusual approach helps avoid the challenges that high winds and waves could pose to safety and maintenance work,” says Pieter Swart, team leader for underwater pipelines on the project.
Engineers still faced a challenge to install the equipment on the sea floor, where a major landslide around 8,000 years ago caused a massive underwater shift in sediment. Over 240 days, they moved in 5 million tonnes of rock to level the seabed, ensuring production and pipeline system could be safely installed.
Sections of pipeline were welded together aboard dedicated vessels and carefully lowered to the seabed. Shell uses small robotic submarines, called autonomous underwater vehicles, to regularly inspect the pipeline.
Autonomous vehicles were also used to install and test the production systems on the sea floor. Shell engineers had already used robots in this way off the coast of Nigeria and in the Gulf of Mexico. But this was a first in seas as rough as the North Atlantic.
“The systems are designed to last for 50 years,” says Pieter. “They are controlled from shore and run extremely efficiently at about 98% capacity.”
Freezing temperatures in pipelines at the bottom of the sea can cause water produced with the gas to form ice blockages. Anti-freeze is pumped in to keep the gas flowing, and later recycled. An automated system – the first of its kind in deep water – delivers just the right amount for greater efficiency.
Know your reservoir
Offshore teams closely monitor changes to the reservoir rock and fluids as production progresses.
“We have a three-pronged approach to reservoir monitoring,” says Todd Noble, responsible for geophysics at Ormen Lange. “By combining different surveys we can more accurately monitor how the reservoir is changing. This provides important information on how to best manage production and future development.”