Sullivan earned a bachelor's degree in finance from the University of Notre Dame and a master's in business administration from the University of Michigan. He runs the independent oil and gas exploration and production company, Sullivan & Company, where he and his father began working in 1976. It operates in three states, primarily in Oklahoma. In 1989, he started an energy-related company of his own, Lumen Energy Corporation, a natural gas gathering company that operated in two states. He served as the chief operation officer for the company until its sale in 2004.