Royal Dutch/Shell's 54-year old chief executive Peter Voser is to retire next year in a surprise early departure he said was driven by a desire for a change of lifestyle.

Voser has run Europe's top oil company since 2009 and led it from sector laggard in the wake of the 2004 reserves crisis to a position of sector leader in the burgeoning industry of liquefied natural gas (LNG).

"After almost 10 years as CEO and CFO and more than 25 years in Shell, I have elected to retire in the first half of 2014," Voser said in a statement on Thursday.

"After such an exciting executive career I feel it is time for a change in my lifestyle and I am looking forward to having more time available for my family and private life in the years to come."

Shell, the last of the western world's top four oil companies to report results, joined its peers in delivering a result that topped market expectations, thanks in part to strong refining and trading performances, and despite production troubles in Nigeria.

Adjusted net profit on a current cost of supply basis rose to $7.5 billion in the quarter from $7.3 billion a year ago and compared with expectations of around $6.5 billion.

Shell did not take a writedown on its unsuccessful Alaskan drilling programme as some analysts had expected.