OSLO (Reuters) - Norway's Statoil (>> Statoil) will triple its output off the coast of Brazil after agreeing to buy a 25 percent stake in Roncador, one of the country's largest oilfields, from national oil company Petrobras (>> Petroleo Brasileiro SA Petrobras) for up to $2.9 billion (£2.16 billion).

The deal announced on Monday fits Statoil's strategy of bolstering its presence in Brazil as it seeks to add new barrels which are becoming more difficult to obtain closer to home on the Norwegian continental shelf.

"This transaction adds material and attractive long-term production to our international portfolio, further strengthening the position of Brazil as a core area for Statoil," said Chief Executive Eldar Saetre.

In exchange, Petrobras will get access to Statoil's unique knowledge of how to pump more barrels from mature fields, Petrobras CEO Pedro Parente said, noting skills perfected in the Norwegian offshore sector.

The agreement consists of an initial payment of $2.35 billion plus "additional contingent payments" of up to $550 million, Statoil said in a statement.

The additional payment related to Statoil's investments into specific increased oil recovery (IOR) projects to be agreed later, Saetre told a news conference.

The deal's structure showed Statoil was betting on increased recovery from the mature field, Sparebank 1 Markets analyst Teodor Sveen-Nilsen said in a note.

"With Statoil's very strong track record on the Norwegian continental shelf for increasing recovery rates, we believe the outlook for increasing recovery rate for Roncador is good," he added.

Roncador, Petrobras' third-largest producing field in the Campos basin offshore Brazil, is estimated to contain around 10 billion barrels of oil (boe) equivalent in place and more than 1 billion boe in expected remaining recoverable volumes, Statoil said.

The Norwegian company said its ambition was to increase the recovery factor by at least 5 percentage points, bringing the field's total remaining recoverable volumes to more than 1.5 billion barrels of oil equivalent (boe).

The production from the field, which started in 1999, stood at around 240,000 barrels of oil per day in November.

After the transaction, Statoil's output off Brazil will increase to 110,000 barrels of oil equivalent per day from around 40,000 boe per day, the company said.

Petrobras will continue to operate the field and will hold a 75-percent stake.

Parente said he expected a Brazilian court to scrutinise the deal, as with previous assets sales which were not put up for open bidding, but said he was confident that the deal would be approved eventually.

"This is a strategic partnership... It makes no sense to have a competitive process because what we want only Statoil has," he added, referring to the sharing of knowhow.

(Reporting by Gwladys Fouche, Ole Petter Skonnord and Nerijus Adomaitis; Editing by Keith Weir)

Stocks treated in this article : Statoil, Petroleo Brasileiro SA Petrobras