Supermajor oil producers are increasingly promoting female executives to oversee marquee U.S. assets.

In the latest turnabout for an industry dominated by men for all of its 159-year history, former Maersk Oil CEO Gretchen Watkins is set to oversee Royal Dutch Shell Plc’s sprawling U.S. business that includes wells and refineries from the Gulf of Mexico to the Pacific Northwest.

Watkins' recruitment by the world’s second-largest oil explorer by market value follows last week’s announcement that BP Plc is appointing Susan Dio chairman of its American unit. Last month, the U.K. explorer elevated Starlee Sykes to regional president for the Gulf of Mexico and Canada.

To date, Occidental Petroleum Corp.’s Vicki Hollub is the world’s highest-ranking female oil executive among publicly-traded companies. Chevron Corp. and Shell have women CFOs, while Exxon Mobil Corp.’s Sara Ortwein leads its U.S. based shale division.

Still, four-fifths of all workers in the oil sector are men, a ratio that places it behind farming and manufacturing. New disclosures from the U.K. operations of Shell and BP show that in many divisions, men get paid at least 20 per cent more on average than women, a gap the companies attributed to a lack of females at senior levels.