Brazil's state-owned oil and gas company Petrobras on Friday signed an agreement with Portuguese corporations Galp Energia and Partex on oil exploration and production.

Brazil's Chief of Staff Dilma Rousseff and Minister of Finance Guido Mantega took part in the signing ceremony in Lisbon.

With its 50 percent stake, Petrobras will be the operator of this project, and the two Portuguese groups will hold 30 and 20 percent stakes.

The project will be launched in four Lusitaniana Basin blocks, off the coast of Portugal, to the north of Lisbon, Petrobras said, adding that the the Camarao, Ameijoa, Mexilhao and Ostra blocks are located at water depths ranging from 200 to 3,000 meters and cover a total area of 12,000 square km.

The initial investment will cost at least 20 million to 30 million U.S. dollars, Petrobras said.

The Brazilian company added that the agreement is the outcome of the memorandum of understanding signed between Portugal's government and Petrobras last year.