Brazil is to tighten control of new oil finds in the Tupi and Libra fields through new oil regulations approved by the country’s lower house of congress.

The regulations will increase the government’s hold over the oil blocks and reduce competition against Petrobras, the state-controlled producer, according to Bloomberg.

The regulations will allow Petrobras to be sole operator of oilfields where licences have not yet been auctioned and hold a 30% stake in joint ventures that bid for exploration licences.

The government expects other oil firms to bid for the rights to explore fields as Petrobras’ partner. Firms offering the highest share of oil output to the government will win the contracts.

The Tupi and Libra fields are estimated to hold eight billion barrels and 15 billion barrels, respectively.