Patience is paying off for an oil reserve area discovered 30 years ago that's now ready to deliver for Norway at a lower cost, energy major Statoil said.

The Norwegian energy major, which is part owned by the government, said it submitted a plan for development to Petroleum Minister Tord Lien for the Trestakk discovery. Confirmed in 1986, the discovery holds about 76 million barrels of recoverable oil equivalent, and most of that exists as oil.

"Trestakk is a good example of what is possible to achieve through spending time on working toward the best concept selection," Torger Rod, the head of project development for Statoil, said in a statement. "By rethinking our concept along with license partners and suppliers, we have arrived at a solution that costs almost 50 percent less than the original concept."

Estimates for Trestakk development were originally around $1.2 billion, though Statoil said the latest assessment was about half that amount.

Statoil said its expenses tied to exploration for the third quarter increased by $170 million to $581 million, while adjusted earnings declined 69 percent year-on-year to $636 million. Production for the third quarter, meanwhile, was about 5 percent lower than for the same period last year, which the company attributed to regular maintenance and a deferral of some of its gas sales.

Production through the end of next year is expected to grow by about 1 percent. Statoil said production from Trestakk is slated to begin in 2019. The project will be tied in to production infrastructure already in place in the Norwegian Sea.

Norway is a lead exporter of oil and gas to Europe.