The Subsea Factory: A Milestone in Offshore Innovation
The subsea factory was Statoil’s technological vision for developing oil fields in challenging environments and great depths.[REMOVE]Fotnote: The first subsea wet gas compressor in the world at Gullfaks – equinor.com The Gullfaks field in the North Sea had long been a vital source of oil and gas for Norway. However, production had declined sharply, and the field was nearing depletion. To extend its operational life, recovery rates had to be increased. But how?
The breakthrough came in 2015 with the development and installation of the world’s first subsea wet gas compressor near the Gullfaks C platform.[REMOVE]Fotnote: Energi24.no. (2015, 15. oktober). Statoil i gang med våtgasskompresjon på Gullfaks. According to Statoil, the technology represented a quantum leap and a major innovation in oil and gas recovery. The wet gas compressor could boost recovery from existing fields and enable production from less profitable ones. The goal was to increase recovery from Gullfaks South from 63 to 73 percent.
The concept was as follows: untreated wellstream flowed into the compressor, was cooled, compressed, and then transported through pipelines to Gullfaks C. Traditionally, this process took place on platforms.[REMOVE]Fotnote: Bergens Tidende. (2015, 17. juni). Milliardmaskin skal snart senkes. By compressing the gas on the seabed and increasing pipeline pressure, the gas could flow more easily to Gullfaks C for further processing.
The compressor measured 40 meters in length, 70 meters in width, and 12 meters in height, weighing a total of 950 tonnes. It was connected to existing pipeline systems 15 kilometers from Gullfaks C at a depth of 135 meters.
The project began in 2008 and was based on multiphase pump technology developed by Framo Engineering (later OneSubsea).
The subsea compressors were based on Norwegian technology. Several suppliers and subcontractors—mainly from Western Norway—were involved. The core of the system, the wet gas compressors, was delivered by Frank Mohn on Flatøy.
A Rocky Start
The subsea factory faced a rocky start. In May 2016, Statoil decided to shut down both compressors for inspection and review. The reason was a leak in the 16-kilometer-long control line between Gullfaks C and the compressor station. It took a long time to install a new control line. In June 2017, the facility was brought back online and has since operated as intended.[REMOVE]Fotnote: Gjerde, K. Ø., Nergaard, Arnfinn, & Norsk oljemuseum. (2019). Getting down to it : 50 years of subsea success in Norway (R. E. Gooderham, Tran.). Norwegian Petroleum Museum and Wigestrand: 250
Fact Sheet
Wet gas compression is a key technology for maintaining oil and gas production on the Norwegian continental shelf. From the 2000s onward, petroleum production in Norway declined significantly. Major, profitable fields were nearing depletion. The solution was to increase recovery from existing fields and begin production from less profitable ones. This required new, cost-effective technologies, including subsea wellstream compression and water injection. Subsea compression enabled longer pipeline distances and the possibility of transporting wellstream directly to shore, reducing the need for costly platform solutions.
Wet Gas Compressors on the Norwegian Continental Shelf
Gullfaks-feltet (2016)
Åsgard-feltet (2016)
Troll C (2020