RIO DE JANEIRO, May 23 (Reuters) - The oil firm to be created from the merger of Brazil's 3R Petroleum and Enauta wants to explore the Foz do Amazonas' basin if state-run firm Petrobras finds oil there, its future CEO Decio Oddone told Reuters.

Enauta has rights over an oil block in Foz do Amazonas, considered the most promising area in Brazil's so-called Equatorial Margin due to geological similarities with nearby Guyana, where Exxon is developing huge fields.

The new firm will wait until Petrobras has obtained authorization from environmental agency Ibama to drill a well in a different block also in Foz do Amazonas. If it proves to be productive, the new firm will also invest there, said Oddone.

"If Petrobras has authorization and finds something there, we will follow," said Oddone on the sidelines of an event in Rio de Janeiro on Wednesday.

3R and Enauta reached a deal to merge last Friday, which if completed would create a company potentially able to produce more than 100,000 barrels of oil equivalent per day.

Oddone said the new firm would look for partners to explore their block in Foz do Amazonas.

"You can't drill this thing alone. This way we share the risk," he said, adding that it could propose a partnership to Petrobras.

Petrobras has been waiting for about a year for Ibama to rule on an appeal made after the agency denied it a license to drill in Foz do Amazonas due to concerns about the impact it could have on the environment and on Indigenous peoples.

Last week Petrobras said it would not do studies requested by Ibama to proceed with the licensing process, because they considered the request unreasonable.

This week, Mines and Energy Minister Alexandre Silveira defended the country's right to explore Foz do Amazonas, and said future Petrobras CEO Magda Chambriard holds the same views.

While it waits, Oddone said the new firm will first look for synergies and then at developing their current assets, but in the future it wants to expand its onshore and offshore portfolios.

"Wherever there are opportunities we'll go." (Reporting by Rodrigo Viga Gaier; Writing by Fabio Teixeira; Editing by Jan Harvey)