Petrobras, as the company is known, is considering the sale of a 60 percent stake in two blocks of refineries in the Northeastern and Southern regions. Each block would have two refineries and logistical assets, and Petrobras would keep a minority stake.

The company plans to keep full ownership of nine other refining units in Brazil_s richest region, the Southeast, according to a presentation the company will show to investors at an event on Thursday.

This partnership model, including the 60 percent stake sale in four refineries and keeping the other nine refineries, will leave Petrobras with a 75 percent market share of refining in Brazil, according to the presentation.

The northeastern block would include refineries, pipelines and terminals in the states of Pernambuco and Bahia, while the southern block includes two units in the states of Paran? and Rio Grande do Sul.

The partnership model to be presented is the result of internal discussions but no final decision has been made, and the company hopes to discuss it with private investors, the filing said.