Corbett held leadership roles at Kerr-McGee Corp. for more than 17 years, including chairman and CEO from 1997 until his retirement in 2006. Earlier, he held various managerial roles at Aminoil Inc., Mitchell Energy Company and Amoco Corporation. He currently is lead independent director for OGE Energy Corp. Mr. Corbett has been a retired business executive since Kerr-McGee Corporation's merger with Anadarko in August 2006. He served as Chairman and Chief Executive Officer of Kerr-McGee from 1999 until August 2006. Mr. Corbett had been with Kerr-McGee since 1985 when he joined the company's Exploration and Production Division as vice president of geophysics. In subsequent years, he held a wide array of senior executive positions with Kerr-McGee. Mr. Corbett also serves on the boards of OGE Energy Corporation and Noble Corporation. Mr. Corbett has been a director of the Company since August 2006.