The giant pre-salt discoveries made by Brazil's state-controlled Petrobras were a game changer for the country’s oil and gas industry more than a decade ago, but perceptions about super-productivity and plummeting exploration risks led the government of the day to create a whole new layer of contracting law for the sector.

The results can be baffling for those unfamiliar with the subject, and even industry veterans can be left scratching their heads in cases where up to three sets of rules can apply to the same unitised field, covering concessions, production-sharing contracts and a transfer of rights in favour of Petrobras.