Transocean Ltd. said Friday that the executive in charge of its worldwide marketing will become chief of staff of the offshore drilling rig company.

Switzerland-based Transocean said that Ihab Toma, executive vice president of operations since August 2011, will become executive vice president and chief of staff on Monday. He will take over responsibility for personnel, supply chain and information technology while continuing to oversee marketing.

The company also said that John Stobart would become executive vice president and chief operating officer on Monday. He had been worldwide drilling manager for BHP Billiton Petroleum since 1994 in Australia, the United Kingdom and the U.S.

Transocean provides services to companies that drill offshore oil and gas wells.

Shares fell 48 cents to $44.89 in afternoon trading.