A field complex in the North Sea has passed a production milestone of 1 billion barrels of product, far more than expected, Aker BP said.

Aker BP, a merger of Norwegian energy companies and a national subsidiary of BP, said the Valhall and Hod complex passed a production milestone ahead of schedule. The production mark is more than three times greater than what was expected when it opened in 1982.

"In 1995, work was performed with the goal to extend the field lifetime and recover more than one billion barrels of oil equivalents," Eldar Larsen, a vice president of Operations at the company, said. "We have now achieved this goal 15 years ahead of what was thought at the time."

Aker BP's milestone follows similar achievements from legacy fields held by Norwegian energy major Statoil. The company's Gulfaks reservoir, first put into production in 1986, passed 2 billion barrels in November. Its Troll field in the North Sea reached its 1 billionth barrel of oil after 20 years in production.

Aker BP had a discovery confirmed by the Norwegian government in December near the Frigg field in the North Sea. Based on preliminary data, the Norwegian government put the estimated size of the discovery at between 25 million and 75 million barrels of recoverable oil equivalents.

Norway is among the leading oil and natural gas suppliers to the European economy apart from Russia. 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.

Larsen said activity in Valhall and Hod has been continuous more or less since operations began in the 1980s, with 55 active wells.

"Our new ambition is to further produce at least another 500 million barrels of oil equivalents," he said.