The prize is called Stabroek — a series of oil fields off the coast of Guyana, the Latin American nation bordering Venezuela and Brazil. The potential riches are incredible — about 11 billion barrels of oil, worth nearly $1 trillion at current prices. And Stabroek is now at the center of a legal battle that hinges on the meaning of a few words contained in a secret document, probably about 100 pages long. The outcome will reshape Big Oil.