I thought they discovered at least decades ago that our oil is actually largely inorganic? It's not dinosaurs & ferns but a direct chemical & physical process. I know a lot of people still say it's just a competing theory but they have found many large deposits in places where it's not possible for it to have been organic. (too deep, in the middle of pure granite with only raw volcanic material and no other organics, etc)

Oil is fluid, so it will not necessarily stay where it is formed, but it will flow through the rocks until it is stopped by impermeable rocks, like granite.

So there is nothing surprising in finding oil elsewhere than where it has formed.

Some hydrocarbons can form in the absence of life, e.g. by Fischer-Tropsch synthesis from syngas, catalyzed by some minerals, where syngas can form in volcanic gases or in hydrothermal vents. However that is likely to have been a negligible contribution to the oil reserves of the Earth and most or all oil ever found has a chemical composition that has clear indications of being produced by the decay of organic matter from living beings.

As far as I understand it, people looking for oil using theories that oil is formed from organic processes have had significantly more success than people looking for oil using inorganic theories, and not for lack of trying on the latter side.

Wikipedia seems to disagree https://en.wikipedia.org/wiki/Petroleum#Abiogenic_petroleum

It's pretty common for hydrocarbons to migrate down from source rocks down into basement along fracture lines or surface weathering, no abiogenesis required.