Peter Voser is to step down as chief executive of Royal Dutch Shell next year after four years in the post, in a surprise move that is expected to trigger a lively race to find a successor. The Swiss national has been named in some media reports as a possible chairman of Roche, where he is already a non-executive director. "He leaves Shell in a much stronger position," said Peter Hutton, of RBC Capital Markets. He has brought real focus to the business. Mr Voser's time as CEO has been marked by the delivery of some of the largest projects in Shell's history, including the $18bn-$19bn Pearl gas-to-liquids development in Qatar. On his watch the company has emerged as a global leader in liquefied natural gas, with massive LNG projects in Russia, Qatar and Australia and a huge LNG trading business. But like its rivals, Shell has struggled to increase production and expand its reserve base in a sector where power has passed from the big international oil companies to state-owned behemoths in the Middle East and Russia. On his watch Shell has made a determined push into new frontiers such as the Arctic and built up a big presence in unconventional fuels like shale gas and tight oil. But Shell's success in the region has been mixed. It has spent $5bn on an oil exploration campaign offshore Alaska, but has yet to complete a single well there, amid ongoing regulatory problems and equipment issues. The company said it would be considering both internal and external candidates to replace him. One contender in the frame is Simon Henry, the company's current chief financial officer. But in a conference call with reporters, he dismissed a question on his chances as "highly inappropriate." Shell said its first-quarter earnings on a clean current cost of supplies basis was $7.5bn, up 3 per cent on a year ago and well ahead of market expectations. The results were helped by improved profit margins in Shell's refining and marketing division as well as increased contributions from trading. Earnings were $1.8bn in the downstream, compared with $1.12bn a year ago. Production was impacted by security problems in Nigeria, where Shell said oil theft is on the increase. Mr Henry said some $5bn-$7bn of oil was being stolen a year in the west African country. Cash flow from operating activities for the first quarter was $11.6bn, while net capital investment was $8.2bn. Production of 3.56m barrels of oil equivalent a day was up 2 per cent on last year. Shell's shares rose 1 per cent to £22.17½ following the news. The shares have increased nearly 50 per cent since Mr Voser took over as CEO but he joined at a time when a low oil price and the global financial crisis suppressed the value of shares in major oil companies.