Origin of oil is very very likely biological:
1) Oil contains coomplex ccompounds that are only found in living organisms (porphyrines).
2) Other compounds (terpenes) are often optically active, not really possible when we assume abiotic oil, however, this would be the rule for compounds from plants or animals.
3) Distribution of chain lengths of hydrocarbons can easily be explained by degredation of more complex compounds (triterpenes, steroids), not by anorganic reaction.
4) Distribution of stable isotopes (13C, deuterium) in not activated groups like alkyl chains of longer hydrocarbons is typical for organic material.
The abiotiv theory was developed by guys who did not know anything about natural compound chemistry and biochemistry.
