Russian geologists say they have data that would support a claim to about 1.2m sq km (463,000 sq miles) of energy-rich territory in the Arctic.
Russia has not staked a formal claim to that area - which is the size of France, Germany and Italy combined, Russian media report.
The geologists spent 45 days studying the Lomonosov underwater ridge.
The Law of the Sea Convention allows states an economic zone of 200 nautical miles, which can sometimes be expanded.
To extend the zone, a state has to prove that the structure of the continental shelf is similar to the geological structure within its territory.
At the moment, nobody's shelf extends up to the North Pole, so there is an international area around the Pole administered by the International Seabed Authority.
The Russian team, from the Oceanology Research Institute in St Petersburg, estimates that the Lomonosov ridge area in the Arctic contains oil and gas reserves of up to 10bn tonnes.
They returned to Murmansk on Monday.
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