EV Energy general partner EnerVest announces management changes EV Energy's general partner EnerVest has named Ken Mariani as president of the company. EnerVest founder John B. Walker will retain the position of CEO and also will continue as Executive Chairman of EV Energy Partners. In this capacity, Walker will focus his daily efforts on acquisitions, institutional fundraising, EVEP and strategic planning. Stephen McDaniel has been named CEO of EnerVest Operating Company, and Jud Walker has been named COO of EnerVest Operating Company. Mariani most recently served as Executive VP of EnerVest, Ltd., and President and CEO of EnerVest Operating Company.