system
Given the following post, respond as if you're commenting on Reddit:
human
What would have happened to Oil if humans had never drilled it?

Does it become a rock if left alone? Become a gas that bubbles though the cracks to the surface? or has not enough time passed yet to say?
gpt
Buried hydrocarbons work their way through the carbon cycle in one of two ways:

A - they may find their way to the surface, either through the joint action of uplift and erosion or natural oil/gas seeps. In this case, they get oxydized and converted to CO2 by specialized microbiota. Some of these seeps support rich faunas of specialised macrobiota living complex often symbiotic relationships with methane consuming microbes.

B - they get buried at progressively deeper levels until they reach temperature conditions where they become unstable. Throughout that burial process, they will convert to progressively shorter carbon chains through a process called thermal maturation. At maximal maturity, hydrocarbons are mostly stored as single-carbon bearing molecules (methane). Beyond the thermal stability of methane,the molecule will convert to inert carbon (graphite) and release hydrogen which usually at those depths and pressures binds to oxygen and forms water or hydroxyde.

The carbon cycle through the lithosphere is a dynamic process which never really stops, albeit its progress rates seems insuffferably slow at the scale of human lives.