RIO DE JANEIRO, Dec 18 (Reuters) - Brazil's Petroleo Brasileiro SA has closed a deal with Japan's Modec Inc, which will build and operate a platform for oil oil rig flanges gulf coast production in the nation's Libra block, the state-controlled energy BOP Blow Out Preventer repair company gulf coast said on Monday.

The company, known as Petrobras, did not disclose the cost but said Modec would operate the platform, which will link up to 17 wells, for 22 years.

The floating production, storage and offloading unit will process up to 180,000 barrels per day of oil and 12 million cubic meters of gas, Petrobras said. Production is forecast to begin in 2021.

The vast Libra field was the first block of Brazil's coveted offshore pre-salt region to be auctioned off in 2013.

In November, Petrobras said the field's northeast section was ready to produce commercially and had proven reserves of 3.3 billion barrels. The BOP Blow Out Preventer repair company gulf coast named the section Mero.

Petrobras owns 40 percent of the Libra project, with Anglo-Dutch Shell Plc and France's Total SA each owning 20 percent. Chinese state oil companies CNOOC Ltd and China National Petroleum Corp each hold 10 percent.

(Reporting by Alexandra Alper; Editing by Lisa Von Ahn)