(CNN) -- The Norwegian energy company Statoil made what it called the largest oil strike of the last 30 years in the North Sea, it said Tuesday.
The company reported the oil field might contain between 500 million and 1.2 billion barrels of recoverable oil. It lies between two previous Statoil fields, Aldous and Avaldsnes.
"Norway has not seen a similar oil discovery since the mid-'80s," said Tim Dodson, Statoil's executive vice president for Exploration, calling it "a giant oil discovery."
The Norwegian company has a 40% stake in the licenses where the connected oil fields are located.
"The Aldous/Avaldsnes discoveries are evidence that the Norwegian continental shelf is still attractive," Dodson said.
But oil experts are skeptical whether the oil discovery is going to have a long-term impact on oil drilling in the North Sea.
"The oil field is giant -- but not supergiant," Steffen Bukold, an independent oil expert based in Hamburg, Germany, told CNN. "I don't think the discovery is going to stop the trend that more and more large energy companies are turning away from the North Sea."
Rafael Sandrea, president of IPC Petroleum Consultants Inc., agreed: "The profiteers of the discovery are the small companies." The North Sea's importance for the oil industry will continue to decline, he said.
Norway is still the seventh-largest oil exporter in the world. The petroleum sector has become the country's largest industry since oil production started nearly 40 years ago. Currently, about 70 oil fields are in production on the Norwegian continental shelf producing 2.1 million barrels of oil in 2010 alone.
But according to the government agency Norwegian Petroleum Directorate (NPD), many of the nearly 500 rigs and facilities on the Norwegian shelf are approaching the end of their scheduled lifetime. The country's total petroleum resources have been reduced by 3.26 billion barrels since 2009. In January NPD forecast Norwegian oil production would fall 6% this year. It would be its 11th year of decline.
Last week an oil spill was discovered at Shell's Gannet Alpha platform in the U.K. North Sea.
The main leak has been stopped but the source of a smaller leak, found Tuesday, has not yet been found. Since last week the platform has spilled about 218 tonnes (1,300 barrels).
As of Tuesday, no oil was expected to reach land and the platform was leaking about a barrel a day, according to Glen Cayley, technical director of Shell's exploration and production activities in Europe, based in Aberdeen, Scotland.
"We believe that the small leakage is coming from a relief valve adjacent to the main leak and from the same source," Cayley said.
A Greenpeace expert who specializes in oil, Joerg Feddern, told CNN, "It is difficult to understand the scale of the spill because of Shell's bad communication policy."
"The news that there's now a second leak from the Shell platform will only heighten concerns over how this episode is being handled," Greenpeace senior oil campaigner Vicky Wyatt said.
CNN's Rick Noack contributed to this report.