National Oilwell Varco Inc. CFO Jeremy D. Thigpen is stepping down to take over as CEO of Transocean Ltd., which owns the largest global fleet of offshore rigs. Thigpen, an 18-year NOV veteran, has served as CFO since 2012. He previously was president of downhole pumping and solutions. Transocean is one of NOV's biggest customers. Chief Accounting Officer Scott K. Duff was named interim CFO, and a search is underway to identify a new financial chief. Duff, who joined NOV in 2004, holds a bachelor's degree in accounting from the University of Texas at San Antonio and is a certified public accountant.