Lundin said one of its appraisal wells in the discovery area encountered a 98-foot column of oil while drilling its appraisal well 16/3-5.
Lundin President Ashley Heppenstall said the company is "extremely pleased" with the latest test, which confirms the reservoir is one of the best in the North Sea.
Norwegian energy major Statoil last year estimated there were 900 million-1.5 billion barrels of recoverable oil equivalent in Johan Sverdrup, twice the previous estimate.
The Norwegian Petroleum Directorate said its latest reserve estimate for its continental shelf was around 480 billion cubic feet of oil equivalents, an increase of 1.5 billion compared to last year's estimate. The government said that, under current market conditions, the increase equates to $268 billion.
Norway is the largest oil producer in Europe and the second-largest exporter of natural gas after Russia. Production is expected to decline this year but rebound by 2014.