Brazilian prosecutors sued Chevron Corp…and…Transocean Ltd for 20 billion reais ($10.6 billion) over their alleged roles in a November oil spill near Rio de Janeiro. The civil suit filed by federal prosecutors in Rio de Janeiro state also seeks to suspend the companies from operating in Brazil...Some legal experts said the action may be a politically motivated suit…The suit could also jeopardize oil companies' plans to step up their presence in Brazil after the discovery of huge offshore reserves…Chevron, which has said it takes full responsibility for the spill, said it has not received any formal notice of the suit and that the spill was staunched in four days with minimal or no damage to the environment. Transocean had similar comments…The document outlining the prosecutor's case…said the fine was to compensate for environmental and social damage. [also refers to Texaco (part of Chevron), Petrobras, Frade Japao, BG Group, Galp]