The recent discovery of potentially vast new reserves of oil and gas off Brazil’s coast looks certain to transform the country into a leading oil-producing nation over the coming decade. No size has yet been put on the fields, although estimates of 50bn to 100bn barrels or more are common. The government is already preparing to spend the coming bonanza on education, poverty relief and other social goods.

But there is still much uncertainty over the “pre-salt” fields – so called because they are trapped beneath up to 7,000 metres of sea water, rock and a hard-to-penetrate layer of salt. Many analysts and industry figures say this could deter investment and open the door to waste and inefficiency.