OSLO, Norway (AP) — Norway's Statoil has received a huge boost to its reserves with the announcement that two previous North Sea oil discoveries are connected which may represent the biggest find in the Norwegian continental shelf in 30 years.

Statoil said in a statement Tuesday that the Aldous and Avaldsnes oil discoveries together contain between 500 million and 1.2 billion barrels of oil — significantly more than previously thought.

Statoil owns a 40 percent stake in both discoveries and is the operator of Aldous.

Tim Dodson, the company's vice president for exploration, called the combined discovery "giant," adding that "Norway has not seen a similar oil discovery since the mid-80's."

The discoveries show the Norwegian continental shelf remains an attractive source for crude, he said

Trond Frode Omdal, an oil analyst at Oslo-based Arctic Securities ASA, said the size of the discovery was surprising.

"I think the companies had almost given up making such a huge discovery in the North Sea," he said, adding that the gross value of the discoveries could be as much as $40 billion.

Omdal said Norway's proven oil reserves amount to 6.7 billion barrels, according to the BP Statistical Review, so a discovery containing 1 billion barrels is significant.

He said last year Norway produced 2.1 million barrels per day and that Statoil's new fields might produce as much as 300,000 barrels per day.

Statoil's stock was up less than 1 percent to 123.5 kroner ($22.6) on the Oslo Stock Exchange.

Meanwhile, shares of Lundin Petroleum, an independent Swedish oil and gas firm that owns 40 percent of Avaldsnes and 10 percent of Aldous Major South, rose more than 6 percent to 84.95 kroner ($13.25) on the Stockholm Stock Exchange Tuesday.

"It's clear that the Avaldsnes/Aldous Major South is a world class find and will probably become one of the largest Norwegian fields that have been discovered in recent times," Lundin Petroleum CEO Ashley Heppenstall said in that statement.

Lundin Petroleum is the operator of the Avaldsnes discovery.