Brazilian state-controlled oil company Petrobras said Friday that it has started up an offshore platform with the capacity to extract 150,000 barrels per day.

Cidade de Ilhabela, a giant vessel that was converted into a floating production, storage and offloading, or FPSO, unit at a Chinese shipyard and which has the capacity to store 1.6 million barrels of oil and house 140 people, began operating Thursday at the Sapinhoa pre-salt field.

That field in the Santos basin is part of the BM-S-9 block, located 310 kilometers (190 miles) off the coast of Sao Paulo state, in which Petrobras has a 45 percent stake and BG Group and the Repsol-Sinopec alliance have 30 percent and 25 percent interests, respectively.

Sapinhoa is one of Brazil's major pre-salt fields, so-named because the oil they contain is located under water, rocks and a shifting layer of salt at depths of up to 7,000 meters (22,950 feet) below the surface of the Atlantic.

That offshore region, the main focus of investment by Petrobras, could vastly increase Brazil's proved reserves and turn the country into a major crude exporter.

The pre-salt area is governed by a special regulatory regime that allows only for production-sharing contracts, not outright concessions.

"The new platform is part of series of production projects scheduled to enter into operation this year under our Business Plan for the 2014-2018 period," Petrobras said in a statement.

In addition to its daily production capacity of 150,000 barrels, Cidade de Ilhabela can compress up to 6 million cubic meters (211.5 million cubic feet) of natural gas per day.

The platform began extracting hydrocarbons after it was connected to the 3-SPS-69 well, which has the capacity to produce 32,000 barrels per day of high-quality crude.

The FPSO will gradually be connected to eight other producing wells and seven water-injection wells until it attains its maximum capacity in the second half of 2015.