what happens to crude oil when it is left alone in the earth?

what happens to crude oil when it is left alone in the earth? i know that crude oil is a biproduct from way back when, but if left alone in the earth what would it "turn" into, if left alone for say, how ever long?

One Response to “what happens to crude oil when it is left alone in the earth?”

  1. Girrl I Says:

    2012.^_^