(Rewrites, adds Petrobras comment, detail on benefits of sale to Petrobras)
RIO DE JANEIRO, Aug 30 (Reuters) - Petrobras' sale of offshore oil rights in Brazil to Norway's Statoil ASA will free up about $11 billion that Brazil's cash-strapped state-run oil company can use to pay debt or develop areas that promise a quicker return, the company's chief executive said on Tuesday.
Of that amount, Petroleo Brasileiro SA - as Petrobras is formally known - will get $2.5 billion directly from Statoil for the July purchase of Carcara, south of Rio de Janeiro, the executive, Pedro Parente, told reporters in Stavanger, Norway.
The rest comes from the boost it will get as it is no longer obligated to invest $7.9 billion to $8.6 billion to transform the Carcara discovery into a productive oil and gas field, its 66 percent share of the estimated $12 billion to $13 billion overall investment needed, he added.
"First of all we are in a period where we need cash," Parente said. "By selling Carcara we will not only receive $2.5 billion, but we will be released from investing another $12 to $13 billion for the field as a whole... We would have had to invest 66 percent of (that) amount."
Petrobras also expects to control per-barrel production costs by redirecting the benefits of the sale to more promising areas closer to existing fields, pipelines and production equipment.
"Carcara is not close to the other fields we have, so by not being close to the fields we would not be able to use the synergies we can use when developing other fields that are closer," he added.
Parente also said Petrobras will meet its goal to sell $15.1 billion of assets by the end of 2016. The target, set in 2015, is designed to slash its nearly $125 billion of debt, the largest in the oil industry.
Statoil said it is excited about developing Carcara, where it expects to produce its first oil after 2020, when older mature fields in Norway will be in decline.
Statoil says Carcara contains 700 million to 1.3 billion barrels of oil and equivalent natural gas, enough for all U.S. oil needs for about two months.
While Statoil has no official estimate for Carcara development costs, Chief Executive Eldar Saetre told reporters on Tuesday that the $12 billion to $13 billion suggested by Parente "is a starting point."
"I think the numbers we are talking about are covering the whole field," Saetre said. "Our target is to go lower on the costs, but it is too early to give a number."
More than half of the oil and gas discovered in the Carcara prospect is believed to extend beyond the BM-S-8 block, in which Statoil bought a stake and will require Brazil to auction off adjacent areas to develop.
Statoil's partners in Carcara are Portugal's Galp Energia SGPS SA (14 percent), Brazil's QGEP SA (10 percent) and privately owned Barra Energia do Brasil Petróleo e Gás Ltda (10 percent). Barra Energia is backed by U.S. investment funds Riverstone Holdings LLC and First Reserve Corp. (Writing by Jeb Blount in Rio de Janeiro; Editing by Dan Grebler and Bill Rigby)