One place where Western oil companies have found open doors is in deep-water exploration, because state-backed oil companies in Russia, China and the Middle East have little experience drilling these tricky wells.

WSJ: Exxon Struggles to Find Oil

Furthermore, so long as it remains government-owned, the company risks being attacked by Brazil's vocal nationalists over its plans to expand its foreign operations, taking advantage of its prowess in deep-water exploration, instead of investing at home.

ECONOMIST: Petrobras