By Gram Slattery and Carolina Mandl

RIO DE JANEIRO/SAO PAULO (Reuters) – A consortium of Brazil’s 3R Petroleum and Norway-linked DBO Energy is in bilateral talks with Brazil’s Petrobras to purchase a cluster of offshore natural gas fields, according to two sources with direct knowledge of the matter.

The Peroa cluster, located off the coast of Espirito Santo state, would be among the first all-gas offshore fields sold by Petrobras amid a larger push to break the company’s near-monopoly in Brazil’s natural gas value chain.

Petroleo Brasileiro SA , as the state-controlled firm is formally known, has long dominated most segments of the Brazilian natural gas sector. But in recent years, it has begun selling off pipelines and assets in transport and distribution, in a move the company and the government hope will spur competition.

Several international firms already produce significant amounts of natural gas in Brazil, as they operate