RIO DE JANEIRO/SAO PAULO, July 5 (Reuters) - Brazil's Petroleo Brasileiro SA is scheduled to hold a final "re-bid" for two oilfields off the coast of Rio de Janeiro on July 8, four sources told Reuters this week, after the state-run oil firm annulled a previous bidding round.
Among the possible bidders for the firm's Pampo and Enchova shallow-water fields are Trident Energy, backed by private equity firm Warburg Pincus, and a group composed of Brazilian independent oil firm Ouro Preto Oleo e Gas, UK-based Seacrest Capital and Anglo-French firm Perenco, said the sources.
A successful sale of the fields would help Petrobras, as the firm is commonly known, in its ongoing drive to reduce debt, a key goal of Chief Executive Roberto Castello Branco. However, the drawn-out nature of the sale has underlined what potential buyers characterize as a bureaucratic and complex divestment process.
Rio de Janeiro-based oil firm Petro Rio SA is also in the running, added the sources, who requested anonymity to discuss confidential matters.
The process kicked off in mid-2018, when Petrobras entered exclusive talks to sell the asset to a consortium composed of Ouro Preto Oleo e Gas and private equity firm EIG Global Energy Partners.
In December, Petrobras opened a final re-bidding round, as mandated by federal rules, in which competing parties could raise or lower their offers as long as they kept the same contractual terms as those agreed upon in the bilateral negotiations.
The Ouro Preto group took advantage of that opportunity to lower its own bid, provoking Petrobras to walk away from the table. Petrobras then began bilateral negotiations with Trident.
In June, Petrobras opened a second re-bidding round after agreeing upon terms with Trident, Reuters reported, and received bids surpassing $1 billion in value. At that point, Ouro Preto presented the highest offer in a re-jigged consortium. Perenco and Seacrest joined the new group, with EIG exiting, the sources said.
However, the Trident group challenged the Ouro Preto bid, arguing that the change in the other consortium - with Perenco taking an equity stake - violated the rules of the tender, the sources said.
Petrobras then annulled the results of the round and set a new re-bid date, saying publicly it was clarifying the tender rules to the involved parties.
Trident and Warburg Pincus declined to comment. All other parties did not respond to requests for comment.
The Ouro Preto group disagreed vehemently with Petrobras' decision, believing its bid followed the rules, three of the sources said. The bid was accepted by Petrobras before the process was scuttled, the sources added.
Both parties are considering participating in the new bidding round, according to the sources.
Pampo and Enchova produced almost 39,000 barrels of oil equivalent per day, according to July 2018 figures, making it the largest mature production asset in Petrobras' divestment portfolio.
Reporting by Gram Slattery and Carolina Mandl Editing by Chizu Nomiyama