Mark A. Houser serves as Executive Vice President and Chief Operating Officer of EnerVest. Prior to joining EnerVest Houser was Vice President, United States Exploration and Production for Occidental Petroleum Corporation ("Oxy"), where he helped lead Oxy's reorganization of its domestic base, including the successful $3.65 billion acquisition of the Elk Hills Naval Petroleum Reserve. Houser began his career as an engineer with Kerr-McGee Corporation. In 1989 he joined Canadian Occidental Petroleum, Ltd. where he held positions of increasing responsibility, including Vice President, Corporate Planning and Investor Relations in Calgary and Vice President - Exploration for CXY Energy, Canadian Oxy's United States subsidiary. He holds a petroleum engineering degree from Texas A & M University and MBA from Southern Methodist University.

Houser and his wife Lou live in Houston with their four daughters. Houser serves on the Administrative Board of Chapelwood United Methodist Church where he also teaches Sunday school. He serves on the Board of Directors of the North American Prospect Expo (NAPE) and is a member of the Board of Directors of the Louisiana Independent Oil & Gas Association (LIOGA). Houser is also a member of the Society of Petroleum Engineers, and the Independent Petroleum Association of America (IPAA). His other interests include playing tennis and coaching soccer, basketball, softball and volleyball teams for his four daughters.