The hunt for Shell’s next chief executive is under way, its chairman said on Tuesday, after CEO Peter Voser made what could be his last appearance at the oil group’s annual shareholder meeting.

Voser announced his surprise decision three weeks ago to step down in the first half of 2014, before his 56th birthday, and less than five years into the role.

“The process has started,” Shell chairman Jorma Ollila told Reuters after the meeting when asked about the succession plan.

Ollila chairs the three-strong nomination and succession committee that will choose Voser’s replacement.

Voser has been a pillar of Shell’s new-found stability since he rejoined the company as finance director in October 2004 as part of a wholesale clearout of disgraced former top management following a reserves accounting scandal.

Employees of the 180-year old Anglo-Dutch group, which traditionally grows its own top executives, believe an import is unlikely to get the top job, but Voser is only the second person to hold the CEO role under a simplified corporate structure introduced in 2005.

A small investor in the company said he expected Shell to appoint someone in Voser’s mould and he thought it likely to be an internal candidate.

“I am not expecting any great changes in management style at all. It will be more of the same at Shell,” Chris White, a portfolio manager at Premier Fund Managers, said.

Inside Shell, the current finance director, Simon Henry, is regarded as a potential frontrunner, along with Marvin Odum, the company’s head of upstream operations in the Americas.

Henry has a mathematics and accounting background even though, like Odum, he joined the company as an engineer. Odum would be Shell’s first American CEO.

Andrew Brown, who became head of international upstream last year, could be a candidate too, as could director of projects and technology Matthias Bichsel.

One company source said Brown’s relatively recent appointment may make him an outside bet, while Bichsel, born in 1954, might be considered too old for the job.

Shell has said it will look outside for Voser’s replacement as well as inside.

Voser leaves Shell with a leading global production and technology position in liquefied natural gas (LNG) and gas to liquids.

Shell is also strong in oil exploration and offshore production in the Gulf of Mexico and West Africa, and has a well-developed relationship with China, where the oil industry has strong growth potential, plus long-term assets in Canadian oil sands.

But the group suffers regular sabotage and theft from its onshore installations in Nigeria, where it is the biggest western producer, and has made little progress with its costly Arctic drilling programme in recent years.

Like its big rivals, Shell is being squeezed by rising finding and development costs as prices and demand stagnate.

The other two members of Shell’s succession committee, drawn from the ranks of its non-executive directors, are Josef Ackermann, the former Deutsche Bank chief, and Hans Wijers, who ran Dutch chemicals group Akzo Nobel until 2012.