In announcing the lawsuit Wednesday, the prosecutor's office in Campos, in Rio de Janeiro state, said Chevron and Transocean "showed a lack of planning and environmental management" by allowing the leak that let an estimated 2,400 barrels of oil to flow into the ocean in November, The Wall Street Journal reported.
Chevron said Wednesday it hadn't received any formal notice of the lawsuit, saying it acted responsibly and that the flow of oil was stopped within four days.
The oil company said less than a single barrel of oil was on the ocean surface now and there was no impact on the coast or wildlife.
Experts on Brazil's oil industry say the companies weren't likely to shut down or pay the damages sought in the lawsuit.
"Unhappily, oil has become political; every prosecutor wants to get on television, and so we get absurd lawsuits like this," Adriano Pires, director of the energy consulting firm Brazilian Infrastructure Center in a Rio de Janeiro, told the Journal. "Nothing is going to happen to Chevron. But what will happen is that it will scare investors, Brazil loses credibility, and the cost of investment goes up."
A Nov. 7 drilling accident caused an oil spill at an appraisal well at the Frade oil field deep in the Atlantic Ocean off the coast of Rio de Janeiro state. Brazilian authorities levied fines and ordered the firm to stop all drilling, but allowed Chevron to drill about 79,000 barrels a day from its other wells.