Nautical Petroleum, the oil explorer that has been enjoying huge success in the North Sea recently, has made further inroads into the seas around Ireland, announcing an agreement that could see it taking a 65% stake in a discovery in the North Celtic Sea.The current operators of the discovery, Providence Resources and its partners, have reached an agreement under which Nautical will receive a 25% stake in their Nemo heavy oil discovery in exchange for work to determine the feasibility of the study.The discovery, Nemo, is estimated to contain up to 230m barrels of oil.Nautical has a further option to increase its stake to 65% and assume operatorship should we elect to drill an appraisal well by the end of 2011.'We continue to build a material portfolio in Ireland in an area which demonstrates considerable exploration and appraisal potential,' chief executive Steve Jenkins said. 'With Nemo we have an opportunity to use our expertise in heavy oil to potentially exploit the resource upside of this discovery.'Providence chief executive Tony O' Reilly said: 'We are very pleased to be collaborating with a company like Nautical that has significant heavy oil expertise that will help unlock the potential of the Nemo discovery and other heavy oil discoveries in the Celtic Sea.'Last week Nautical and Providence, had the area covered by licensing option 10/01, also in the North Celtic Sea, extended