Repsol along with its partners at the China Petroleum and Chemical Corp., Brazil's Petrobras and British energy company BG Group said it made a significant oil discovery about 170 miles off the coast of Sao Paulo.
The Spanish energy company said it found an oil reservoir about 650 feet thick containing medium-grade crude oil.
"Brazil's offshore boasts one of the world's fastest-growing oil and gas reserves," said Repsol in a statement.
The discovery was made in a new well in the Santos Basin in water depths of more than 7,000 feet.
Repsol and the Chinese company last year signed an agreement to develop Brazilian assets jointly, creating one of the largest energy companies in Latin America.