AIM-listed Northern Petroleum has announced its exploration and technical director is planning to retire at the end of 2014. It also revealed that the role of chief operating officer will this month be taken on by Paul Lafferty, who is joining the group from the exploration and production division of E.ON, where he was the general manger of operations.Chairman Jon Murphy said: "[Heard] has made a tremendous contribution to Northern Petroleum over the past 12 years, both with his technical expertise and the leadership that he has provided to the staff.""[Lafferty's] recruitment has significantly strengthened our production and operations expertise in line with our strategic direction of production led growth," added chief executive officer Keith Bush.Shares had fallen 1.1% to 19.90p by 12:16.NR