Norwegian energy company Det norske said Thursday it's one of the largest operators in the region now that it closed on an acquisition of a Marathon subsidiary.

Det norsk oljeselskap paid $2.7 billion total for the subsidiary in a deal unveiled in June.

"The sale of the Norway business was one of Marathon Oil's strategic priorities for 2014 and a continuation of our portfolio optimization strategy," Marathon President Lee Tillman said in a statement.

The sale includes the Alvheim floating production, storage and offloading vessel and 10 licenses in the Norwegian waters of the North Sea. Marathon said it produced an average 80,000 barrels of oil equivalent from its Norwegian assets last year.

Det norske said Thursday the acquisition makes it one of the largest operators in the region.

"We are acquiring a solid portfolio with high production rates and significant operational experience that adds to Det norske's exploration and development capabilities," Chief Executive Karl Johnny Hersvik said in a statement.

The Norwegian Petroleum Directorate, the nation's energy regulator, said average daily production for September was about 1.47 million barrels of oil per day, 2.5 percent above what NPD had expected and 10 percent higher year-on-year.