* Watkins to replace Bruce Culpepper at end of year
* Watkins to also replace shale boss Greg Guidry(Adds details, background)
By Ron Bousso
LONDON, March 27 (Reuters) - Royal Dutch Shell'sU.S. boss, Bruce Culpepper, will step down at the end of theyear and be replaced by former Maersk Oil Chief ExecutiveGretchen Watkins, the company said in a statement on Tuesday.
Shell's head of unconventionals, Greg Guidry, who overseesthe Anglo-Dutch company's shale production in North America andArgentina, will step down on June 31, when he will be replacedby Gretchen.
Watkins will retain her role as head of unconventionals whentaking over as Shell U.S. country chair, the company said.
Shell, which has large offshore production and a number ofrefineries in the United States, has earmarked its shalebusiness as a key growth engine for the next decade.
It aims to boost its overall shale production by 200,000barrels of oil equivalent per day (boe/d) to 500,000 boe/dbetween 2017 and 2020, mostly in the United States with someproduction in Argentina, Guidry told Reuters inMarch.
North America accounted for roughly one fifth of Shell'stotal oil and gas production in 2017 and over one third of itsrefining capacity.(Reporting by Ron Bousso, editing by Louise Heavens and DavidEvans)