Scott Sheffield has served as Chairman of the Board since August 1999, and previously held the positions of Chief Executive Officer for the Company from August 1997 through December 2016, and President from August 1997 to November 2004. Mr. Sheffield also served as Chairman of the Board of Directors and Chief Executive Officer of Parker & Parsley, a predecessor of the Company, from January 1989 until the Company was formed in August 1997. He joined Parker & Parsley as a petroleum engineer in 1979, was promoted to Vice President - Engineering in September 1981, and was elected President and a Director in April 1985. Before joining Parker & Parsley, Mr. Sheffield was employed as a production and reservoir engineer for Amoco Production Company. Mr. Sheffield also serves as a director of The Williams Companies, Inc., a provider of large-scale infrastructure for natural gas and natural gas products, on the advisory board of the Center for Global Energy Policy at Columbia University, and on the Energy Council of CSL Capital Management, LLC, a private equity firm. Mr. Sheffield is a distinguished graduate of The University of Texas with a Bachelor of Science degree in Petroleum Engineering.