Shares in Desire Petroleum jumped 13% on the news that there may be more oil than expected in one of its licences off the Falkland Islands.Fellow North Falkland Basin oil and gas group, Rockhopper Exploration, said new seismic data suggested that more oil could be found in its Sea Lion Main Complex."The company believes that up to approximately 10% additional volume could be contained within licence PL004, in which Rockhopper has a non-operated 7.5% working interest," Rockhopper said. The remaining 92.5% interest is held by Desire.Rockhopper raised its 'low case' estimate for stock tank oil initially in place from 516m to 608m barrels. "Since Desire does not have access to all the data upon which Rockhopper's evaluation is based, in particular the 14/10-6 well data, Desire is unable to confirm Rockhopper's interpretation at this stage," the firm said in a statement. Investors at Desire Petroleum were given a reason to buy in May after the company announced positive 3D seismic data from the East Flank Play Fairway. It has been a rough year for Desire investors, who have seen their shartes plummet by 80% in the last year, following a number of well disappoints and a well abandonment.