I'll throw my 2¢ in,

Worked the oil patch for 18 years, petroleum engineering from USL, blow out prevention school, API production standards, etc etc.

While not acknowledged academically, it was openly discussed in the mid 80s, oil has multiple sources of origin.

Directional drilling lead to more robust tools of oil analyzation, (determining if your neighbor was pumping your oil field dry) mass spec. started deciphering differences in oils from specific field and origins.

Some oil is the byproduct of continuous decomposition of organic matter under pressure, while some oil is the byproduct of the earth's crust constantly recycling itself tru the core.

Shale oil or rock oil is a example of the latter. Supposedly there are massives field of shale oil under the grand canyon, and many other places where faults lie as well.

Cost of production is the problem, much cheaper just to pump it out of producing zones beneath cap rock under pressure.

Leaving all that aside, north america has oil reserves to last 100s if not a 1000 of years. The discoveries of massive reserves have been suppress over several decades that I am personally aware of. And this is just north america, occasionally I hear of "white elephants" being discovered in the Arctic.

This peak oil bull has always been just a contrived controversy to control the cost and distribution of energy.

Control the energy, control the economy...