The Window of Oil Generation As burial continues and temperatures climb into what is known as the "oil window" (typically between 60°C and 120°C), a remarkable chemical process called catagenesis takes over. This process, known as diagenesis and catagenesis, transforms organic matter into the hydrocarbons we rely on, buried deep within the Earth's crust.
How Oils Form Deep Underground: The Process of Diagenesis, Catagenesis, and Migration
During this stage, the buried organic matter, now termed kerogen, undergoes physical compaction. Common reservoir rocks are sandstone and limestone.
Sealing the reservoir is the cap rock, typically an impermeable formation like shale, salt, or anhydrite. Burial and Initial Transformation Over time, the accumulation of new sediment layers continuously buries this organic-rich material.
How Oils Form Deep Underground: The Transformation Process
Buoyancy, driven by the oil's lower density compared to surrounding water-saturated rocks, causes the hydrocarbons to migrate. This cap rock is the essential lid that prevents the oil from escaping to the surface or into other geological layers, ensuring the oil remains contained until discovered by humans.
More About How are oils formed
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