Jan. 7 (Bloomberg) -- Petroleo Brasileiro SA, Brazil’s state-controlled oil company, cut its purchases of Bolivian natural gas after Brazil’s power-grid operator banned thermal- power generation in the southeast of the country.

Petrobras, as the company is known, is maintaining imports at levels that allow it to avoid paying for more gas than it needs under its contract with Bolivia, the Rio de Janeiro-based company’s press office said today in an e-mailed response to questions. Petrobras reduced its imports as of Jan. 1.

Grid manager Operador Nacional do Sistema Eletrica shut thermal-power plants, many of them operated by Petrobras, after rains filled reservoirs, making cheaper hydroelectric power available, Petrobras said.

In Brazil’s southeast and central west, which includes Rio de Janeiro and Sao Paulo states, reservoirs were 56 percent full in December, compared with 46 percent a year earlier, according to the operator’s Web site.

Under the contract with Bolivia, Brazil must buy an average of 24.8 million cubic meters of gas a day over the course of a year and a monthly average of no less than 19 million cubic meters a day, Petrobras said.

If imports fall below the minimums, Petrobras still has to pay for the gas it doesn’t use. Petrobras has the right to buy as much as 30 million cubic meters of gas a day, the maximum that can be shipped through the pipeline that links the two countries.

To contact the reporter on this story: Jeb Blount in Rio de Janeiro at jblount@bloomberg.net

Last Updated: January 7, 2009 15:39 EST