Brazil is holding an auction for exploration of four pre-salt oil fields.
Thursday's bidding is being closely watched in the wake of a truckers' strike over fuel price hikes that led to the resignation of the CEO of state oil company Petrobras.
More than a dozen companies, including Petrobras, are participating in the auction.
Last year, for the first time the government gave private companies the chance to operate pre-salt fields alone. It was part of President Michel Temer's plan to increase foreign investment and give Petrobras more independence to set fuel prices.
However, Petrobras' future is in doubt on the heels of a truckers' strike last month that brought Latin America's largest nation to a halt. The strike ended when the government agreed to temporarily subsidize diesel prices.