(Adds details, context)
Initial estimates place the amount of recoverable oil from the Golfinho field at 150 million barrels, the state-run company told the security and exchange commission CVM in a statement.
The field lies some 60 kilometers from the Espirito Santo state capital Vitoria.
The reservoir is at a water depth of 1,374 meters, the statement said.
Due to its proximity to existing infrastructure, production could quickly begin, it said.
Petrobras has announced in recent months a series of discoveries in subsalt clusters at great depths at sea. (Reporting by Mair Pena Neto, writing by Raymond Colitt; editing by Carol Bishopric)