The Twilight of the Western Oil Majors http://www.foreignpolicy.com/articles/2010/04/26/the_twilight_of_the_western_oil_majors

Brazil is home to one of the last major oil frontiers in the world -- and a case study for how the balance of power in the international oil industry is shifting. In 2007, 10 years after the Brazilian government opened its oil industry to foreign investment, the state oil company Petrobras struck one of the richest oil veins in decades. Western oil companies such as Chevron, Total, and BP, thrilled by the rare prospect of a new exploration opportunity, lined up eagerly to invest. 

But the outsiders have been stymied. Brazil, generally one of Latin America's most investment-friendly countries, is now boosting the state's role in developing its vast new oil reserves. And it's doing so with help from China, which has recently provided Petrobas with a massive loan, making the old titans of Big Oil increasingly superfluous