The Norwegian energy company said its Byrding field started production on time and under budget. The field is located north of the Troll field in the North Sea and investments there were reduced by about 70 percent in part because of assets nearby.

"Good utilization of existing infrastructure has resulted in a cost-effective development that will add profitable resources to the Troll field," Gunnar Nakken, a senior vice president for regional operations, said in a statement.

Oil from the Troll field will be included in the basket that makes up Brent, the global benchmark for crude oil prices, starting next year.

Statoil, which is partially owned by the Norwegian government, closed early this year on an agreement to take on the 25 percent stake in the Byrding field from a regional subsidiary of German energy company Wintershall, increasing its operating interest to 70 percent.

Development plans for operations at Byrding were submitted last year. Any oil and gas pulled from the field would be piped through existing networks. Statoil estimates the field will stay in production for about a decade.

The Norwegian government reported a preliminary rate of oil production at 1.55 million barrels per day, lower than expected. Total oil production to June, however, was 1.3 percent higher than expected, based on the preliminary figures.

Statoil reported adjusted earnings for the second quarter of $3 billion, up from the $913 million reported in the same period last year. The company attributed the gains to strong operational performance, improved production and higher prices for oil and natural gas.

Equity production for the company was about 2 percent higher than second quarter 2016, and it said it expected production growth of around 5 percent for the year.