Royal Dutch Shell has sought to calm concerns about diminishing oil reserves and access to new supplies, arguing that its existing resource base will provide 55 years of production at current production levels. "We still have a lot of legacy [positions] from the past,'' said Jeroen van der Veer, Shell's chief executive, in an interview with the Financial Times. Mr van der Veer's confidence comes in spite of increasing uncertainty surrounding international oil majors, many of whom are finding it difficult to explore new sources of oil amid rising costs and increasing nationalism in oil-rich countries, which control more than 80 per cent of the world's crude oil resources. Shell has "20 per cent of [its] balance sheet", or $30bn (