350 km of submarine cables bring renewable electricity to the giant compressors that will extend life of Statoil’s North Sea gas field
ABB has delivered its second power-from-shore system to Troll A, the world’s largest offshore gas platform, which is operated by Statoil and located in the North Sea about 70 km west of the Kollsnes onshore gas treatment plant, outside Bergen.
As with the first system, the purpose is to power two compressors that have been fitted to the platform’s topside to compensate for decreasing pressure in the reservoir. The 3,000 ton compressor modules were fitted last year and began operation in October 2015.
Electricity is delivered using ABB’s HVDC Light technology, which takes alternating current (AC) from Norway’s national grid, converts it to direct current (DC) and transmits it to the platform using a series of 70 km-long cables. When the electricity reaches Troll A, it is converted back to AC to run the compressors.
ABB provided the onshore and offshore converter stations, laid two pairs of DC cables as well as a three-phase AC cable for other power requirements. It also provided the 50 megawatts (MW)/60 kilovolts (kV) high-voltage motors that will operate the compressors.
“This project is an important milestone for ABB as our products are enabling increased production and safeguarding the delivery of natural gas to the European market. And with power from shore, the recovery increase can be achieved in a sustainable and profitable way,” said Per Erik Holsten, Managing Director for ABB’s Oil, Gas and Chemicals business.
Onshore electricity has a number of advantages over offshore generation. Ninety-six per cent of Norway’s electricity comes from renewable sources, so Troll will be a low-carbon operation. A power from shore system has a higher level of efficiency and reliability, with fewer moving parts requiring service. Moving away from gas turbine generation offshore means more gas available for sale and frees up valuable space on the platform.
Since it first brought HVDC cables to the market in the 1950s, ABB has been responsible for about half the global installed base. In the oil and gas industry it has pioneered power from shore, and was recently awarded the contract for a 100 MW/80 kV connection to the Johan Sverdrup development, 150 km west of Stavanger.
The Troll field was discovered in 1979 and found to be commercially viable in 1983. The 472 meter high Troll A platform is the tallest structure ever to have been moved by mankind. Gas production started in 1996 and at that time the power needs of the platform were met by a 20 megawatt AC cable provided by ABB.
