I'm referring to T. Gold's theory that terrestrial petroleum may be abiogenic. Gold argued:
1. The geographical distribution of oil seems derived from features much larger in scale than individual sedimentary features.
2. The quantities of oil and gas available are hundreds of times those estimated on the basis of biological origins.
3. The so-called "molecular fossils" found in oil and claimed as proof of a biogenic origin are simply biological contaminants, particularly bacteria that feed upon the petroleum.
4. Petroleum is largely saturated with hydrogen, whereas buried biological matter should exhibit a deficiency of hydrogen.
5. Oil and gas are often rich in helium, an inert gas which biological processes cannot concentrate.
6. The great oil reservoirs of the Middle East are in diverse geological provinces. There is no unifying feature for the region as a whole and, especially, no sediments rich in biological debris that could have produced these immense concentrations of oil and gas.
Anyway, the Siljan Ring in Sweden, an ancient 70km diameter meteor impact was drilled in the late '80s to a depth of 10km. The idea was the impact had fractured the overlying rock to a depth exceeding 40km and this fracturing would allow the postulated abiotic hydrocarbons to seep upwards to a recoverable depth. The last I heard was the results were inconclusive. Because the theory seems dormant today, I assume it may be either unverifiable or has been debunked. Here's a link which gives a synopsis of the theory:
http://www.rense.com/general58/biot.htm
Mariss