Petrobras and Spanish-Chinese joint venture Repsol Sinopec are handing back exploration rights at the Piracuca Field in the Santos Basin due to lack of commercial viability, the companies said.

Brazil's oil regulator, ANP, said the companies had given up the concession to explore the oil and gas field, which was awarded by the government in 2000, according to a statement in Brazil's Official Gazette.

Piracuca was declared commercial in 2009, but further studies showed the area was not commercially viable, Petrobras said in a statement sent to Reuters.

It did not elaborate on any possible financial charges related to the decision.

Repsol Sinopec told Reuters in a statement that it has booked a charge, but did not elaborate on its value.