A Soccer Field-Sized Subsea Template En Route to Åsgard Field

The 1800-tonne subsea template for the Åsgard subsea gas compression pioneering project is en route from the shipyard in Egersund to the Åsgard field in the Norwegian Sea.

Subsea compression will increase recovery from the Åsgard-field by 280 milion barrels of oil equivalent when it comes on stream in 2015.

Three modules have been completed: a subsea compressor station and a manifold to be installed on the Åsgard field at water depth of 300 metres and a module powering the new subsea system to be installed on the Åsgard A platform.

“Together with our partners we are constructing the world’s first subsea compressor,” says Margareth Øvrum, executive vice president for Technology, Projects and Drilling (TPD) in Statoil. “This is a quantum leap in subsea technology. I am pleased to see the end of the first project phase.”

The modules are shipped on barges northward to the Åsgard field. When they arrive on the field one of the world’s largest crane vessels, Saipem 7000, will lower the two units onto the seabed at water depth of 300 metres and lift the power module onto the platform. Pipe-laying on the field started in April.

The dimensions of the subsea modules are huge: the manifold has a length of 34 metres, a width of 27 metres and a height of 15 metres. The subsea template housing the compressors measures 74 X 45 x 26 metres.

“This subsea template is among the biggest in the world, equivalent to the size of a soccer field,” says Øvrum. “When it is placed on the seabed, we must make sure that it is absolutely level.”

Future-oriented technology

After some time the pressures of the Midgard and Mikkel reservoirs become too low to maintain the current production level on the Åsgard B platform. A compressor solution is therefore required. A subsea gas compressor is even more efficient than a conventional platform-based compressor.

“Subsea gas compression is based on future-oriented technology,” says Øvrum. “In addition to being an efficient tool for increased recovery, this is a huge technological leap in subsea development, and an important step on the way towards a complete subsea factory.”

Opening up new possibilities for Statoil in deeper waters and in areas further offshore, this technology enables operations in areas that would have been inaccessible without this technology, such as the Arctic.

Preparing for operation

Even though it will take two years before the subsea system comes on stream, the operational preparations have already started. The Åsgard A personnel have for a long time been making detailed plans for reception and hook-up of the module that will power the subsea system.

The onshore base for the Åsgard subsea gas compression, which has been allocated to Vestbase in Kristiansund in Western Norway, is beginning to take shape. The facilities for cleaning, maintenance and storage of a complete spare set will be ready in about a year.

“Operation of the world’s first subsea compression facility poses many new challenges, and marks the beginning of a new era in subsea system maintenance,” says Astrid Jørgenvåg, head of Åsgard area operations.

“We are establishing new multidisciplinary arenas for interaction, both internally and externally, to make sure that we reach our ambition of sustained high regularity and stable operation.”

Challenging ground-breaking work

Extensive technology and project work still remain before the plant is ready for production in 2015.

Work is being pursued to develop the actual heart of the technology which will separate gas and condensate before the gas is compressed and piped to the Åsgard B platform.

“Our next milestone is to verify the actual compressor technology,” says Margareth Øvrum. “This is ground-breaking technology and demanding work which is well under way.”

The 22 modules constituting the compressor technology will be installed inside the compressor station next year.