1. Organic Matter Accumulation:
- Tiny marine organisms like plankton and algae die and sink to the ocean floor.
- In oxygen-poor environments, these organisms are buried under layers of sediment like clay and sand.
2. Burial and Pressure:
- Over time, more sediment accumulates, creating immense pressure and heat on the buried organic matter.
- The lack of oxygen prevents complete decomposition.
3. Transformation:
- Under the intense pressure and heat, the organic matter transforms into a waxy substance called kerogen.
- This process is called diagenesis.
4. Oil and Gas Formation:
- As the kerogen is buried deeper and exposed to even higher temperatures, it further transforms into oil and natural gas.
- This process is called catagenesis.
5. Migration and Accumulation:
- The oil and gas migrate upwards through porous rock formations, often finding pockets of impermeable rock (traps) where they become concentrated.
6. Reservoir Formation:
- These traps, often consisting of sandstone or limestone, hold the oil and gas, forming what we call reservoirs.
Key Factors for Petroleum and Natural Gas Formation:
- Source Rock: Must contain sufficient organic matter.
- Reservoir Rock: Porous and permeable to allow oil and gas to flow.
- Cap Rock: Impermeable layer that prevents further migration of oil and gas.
- Temperature and Pressure: Specific temperature and pressure ranges are needed for the transformation of kerogen into oil and gas.
Types of Fossil Fuels:
- Petroleum (Oil): A liquid hydrocarbon mixture found in underground reservoirs.
- Natural Gas: A gaseous hydrocarbon mixture consisting primarily of methane.
Important Note: It takes millions of years for these processes to occur, highlighting the importance of fossil fuels as a non-renewable resource.
