Repsol and its partners at Norwegian energy company Statoil and Brazil's Petrobras announced the discovery of oil in a deposit in the lauded Campos Basin dubbed Gavea.
The Spanish energy company in a statement said the find was the "most significant" made in the region but added it was analyzing well data before moving ahead with evaluation of the find and exploration plans.
The Stena Drillmax I drillship positioned itself about 120 miles off the coast of Rio de Janeiro to drill a well in a water depth of 8,885 feet.
Executives and regulators involved in the energy sector are reviewing safe operations of hydrocarbon exploration in deep waters following the BP disaster in the Gulf of Mexico.
The Brazilian well is nearly twice as deep as the Macondo well that failed last year in the Gulf of Mexico, leading to one of the worst disasters in the history of the oil industry.