|MadSci Network: Chemistry|
I visited http://minerals.usgs.go v/minerals/pubs/commodity/ but didn't see any reference to crude oil or petroleum as a commodity. Crude oil is definitely an organic compound. One of my favorite sites is the American Petroleum Institute, which is full of interesting and historical facts related to the oil industry, a must read web site.
There are certainly theories behind the sedimentation process, but that is not the only theory. Please search for yourself to learn more.
Try the links in the MadSci Library for more information on Chemistry.