Oil - a fossil fuel or a mineral?

This is in the nature of a question.

Wandering around the interweb I have found quite a bit of debate as to whether crude oil is actually, or entirely, a fossil fuel.  There is some speculation that oil is – possibly in part – a mineral created abiotically at depths where heat from the mantle and pressure synthesizes carbon and other elements into crude oil.

One of the arguments is that crude has been recovered at depths below the lowest fossil depths.  The latter being about 2,600 meters down.  Whereas crude oil has been recovered from depths way below that.  maybe 8,000 to 10,000 meters down.  I do acknowledge that one cannot simply take the length of a bore as a guide to depth because of the horizontal drilling that oil exploration is capable of (Deepwater Horizon was doing that – apparently).

Anyway, has anyone else any thoughts or evidence or whatever?