It is often claimed that crude oil forming is a process that takes millions of years. However, under the right circomstances, this can happen within an hour. See: Algae to crude oil: Million-year natural process takes minutes in the lab
What you need for that are:
- Bio material (like algea)
- Heat (350 degrees celsius)
- Pressure (3000 psi, or 2 km deep water)
A global flood would provide enough water… and enough bio material, as it is ripped off everywhere… and enough heat. All flood models that are available show that there must have been a lot of heat involved during the flood.
Generating crude oil takes millions of years, or a global flood.