Oil and gas extraction causing depletion and thereby reducing the amount available for extraction is NOT evidence that abiogenic oil & gas does not exist, or is too small a proportion of extracted fuel to be significant. Also, it turns-out that fully-depleted wells have been known to regenerate themselves. Quite a few in the Gulf of Mexico that were shutdown in the 70s and 80s were checked, and they had regenerated somewhat. The FACT is that methane, in particular, is a very simple molecule and is abundant. Your example of Titan shows that it doesn't require life to create. The Russians have long felt that abiogenic oil is a thing, and drill just about everywhere. They have lots of oil, and it seems to come from everywhere. There could well be processes within the Earth that can create the relatively-simple hydrocarbon molecules. The main part of refining oil is to get rid of nasty contaminants such as sulphur. I think dismissing the concept of abiogenic oil is based-upon superficial reasoning. Oh, and the kind of "oils" that make up flora and fauna are NOT the same as petroleum!

I too have a ecucaion in geology. And as far as know, there are some Brazilian offshore oilfields that are 8000 meters deep down. It might be a very rare case of abiogenic oil, but it is rare, and stull possible. Oil and gas under volcanic rock is often described as abiogenic oil, and a proof of unorganic origin, but when the volcanic rock is much younger than the underlaying sedymentary rock it points to organic oil. But when we had the oil crisis in 1973, the oil would end in 1980. Obama was wrong when he told us that there isn't more oil to find. The sources is just being redefined. With the known resourses today, we can have oil and natural gas for about 500 years. The origin of the resources is just an academic question. +46 722 082 899.