The state-led company said its Pitu well, 1-BRSA-1205-RNS, found a hydrocarbons column 188 metres thick as the well was drilled to a total depth of 5353 metres.
Petrobras had first reported the presence of oil shows to regulators on 17 December. Tests confirmed oil of 24 degrees API for the discovery.
Petrobras operates the BM-POT-17 block with an 80% share with Portugal's Galp on 20%.
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