Matrix recommends buying shares of North Falkland Basin-based oil and gas group Rockhopper Exploration following the positive resource update on Monday.Rockhopper 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," the statement said.New estimates for stock tank oil initially in place for the low, mid and high cases are 608m barrels, 1,086m barrels and 1,279m barrels, respectively."Our current target price of 400p is based on 155mmbls for the Sea Lion discovery. This morning's announcement is very positive, and we will be reviewing our valuation to incorporate new volume estimates," said analyst Charlie Sharp.For now, the target price stands at 400p.Shares jumped 7.58% to 234,25p at 12.34pm.BC