By Margot Patrick Of DOW JONES NEWSWIRES LONDON (Dow Jones)--U.K. oil and gas company Fairfield Energy PLC Thursday said it aims to raise up to $500 million on the London Stock Exchange as part of a plan to increase production at its North Sea oil fields. Fairfield Chief Executive Officer Mark McAllister told Dow Jones Newswires it will use the funds to add production at its existing Dunlin fields, as well as for development and further exploration at other fields it owns. Fairfield Energy was set up five years ago with financial backing from a consortium of investors led by U.S. private equity firm Warburg Pincus. Its aim is to buy and develop mature oil fields in the North Sea being sold off by big incumbents such as Royal Dutch Shell PLC (RDSA, RDSB) and BP PLC (BP), as these companies switch their focus to fresh opportunities elsewhere in the world. Fairfield bought its four producing fields--Dunlin, Dunlin SW, Osprey and Merlin--from Shell two years ago. "There are still an awful lot of assets in the North Sea in the hands of the majors, so there is plenty of room to turn them into valuable properties," McAllister said. New shares to raise between $450 million and $500 million will be issued around mid-July, McAllister said. The company's existing investors aren't selling any stock under the offer, apart from a 15% potential over-allotment, and have a 180-day lockup once the shares start trading. Credit Suisse Securities and Goldman Sachs are joint global coordinators and joint sponsors of the share sale. Hawkpoint Partners is financial adviser and joint sponsor. -By Margot Patrick, Dow Jones Newswires; +44 (0)20 7842 9451; [email protected] (END) Dow Jones Newswires June 17, 2010 08:15 ET (12:15 GMT)