Penn West (NYSE: PWE) is about to change the nameplate on its CEO's office. The company announced that current Chief Executive and President Murray Nunns has announced his departure, effective July 1. Starting June 19, his place will be taken by David Roberts, onetime executive vice president and chief operating officer of Marathon Oil. Penn West said it intends to name him to its board of directors once he takes up the CEO post.

Roberts is an oil industry veteran with more than 30 years of experience. Before his time at Marathon Oil, he also served in executive positions in BG Group and Chevron.