I am not able to access my resources at the moment, but if I recall from school, a particular politically powerful Russian scientist essentially mandated that the abiogenic petroleum theory would be the one accepted by the Russian establishment. At the time, they justified this by pointing to large oil fields for which source rocks (underlying rock containing thermally decomposed organic matter) had not been discovered. Of course since then the source rocks have been discovered.

Amusingly, if you Google "abiogenic petroleum theory" you will find lovely quack articles explaining how plausible the theory is and how it means we will never run out of oil.