Methane hydrate litters the ocean floor. Plate induction would carry some (most?) of it under the adjoining plate. The methane hydrate would cook off quickly and rise to the bottom of the plate above. You now have a simple hydrocarbon in the presence of oxygen and under great heat and pressure. The basalt would cook off more slowly and rise as granite next.
There is your oil layer and impervious layer and a source of micro-fossils.
If this is correct the entire hydrocarbon system is naturally recycling itself over geologic time.
Induction zones are a small fraction of the ocean floor.
The methane hydrate would cook off quickly and rise to the bottom of the plate above.
Okay, to the bottom of the impervious granite...
You now have a simple hydrocarbon in the presence of oxygen and under great heat and pressure.
What oxygen source?
Heat and pressure beak down carbon bonds, not form them.
There is your oil layer and impervious layer and a source of micro-fossils.
No oil, and below the plate with impervious layer of granite separating it from the sedimentary layers where we produce oil from.
If this is correct
Lots of flaws here...
Also note lots of oil found thousands of miles from subduction zones.
And still doesn’t explain how in the sedimentary layer, different types of oil found under different layers of sealing rock.