Following an uptick in oil production, and after boasting of legacy output this week, Norway's Statoil said one of its fields has passed 2 billion barrels.

Explored first in the 1970s and put into production in 1986, the Norwegian energy company said its Gullfaks reservoir has delivered 2.6 billion barrels of oil.

The Norwegian Petroleum Directorate signed off on the extended use of the so-called B platform on the Gullfaks field through the end of 2035. In asking for extension, Statoil early this year said the field could be profitable at least through 2031, and potentially longer if the right conditions are in place.

Development for Gullfaks could add another 18 million barrels of oil equivalent to net Norwegian production. Compression methods utilized to squeeze more fossil fuels from the basin could add another 22 million barrels of oil equivalent to Gullfaks output.

Early this week, Statoil boasted that its Troll field in the North Sea reached its 1 billionth barrel of oil after 20 years in production. The company said that, despite sidelining some operations this year, the combined production from the Troll field so far represents about $150 billion.

Statoil said production has been relatively flat over the last few years, but the company forecasts another eight to 10 years of production left in the field in the Norwegian waters of the North Sea. Gullfaks production could last into the early 2040s.

Norway is among the leading oil and natural gas suppliers to the European economy apart from Russia. The government reported preliminary data for November show an average production of 2.15 million barrels of oil, natural gas liquid and an ultra-light product called condensate, which is about 2 percent higher than figures from October.