Sealing the reservoir is the cap rock, typically an impermeable formation like shale, salt, or anhydrite. The type of kerogen present—classified as Type I, II, or III—largely dictates the potential for generating oil or gas.
Burial Compaction Heat Driving Oil Generation Mechanism
Source Rock: The Organic Foundation The first critical step in oil formation begins with the accumulation of organic material in an environment rich in nutrients. Here, they mix with sediments like clay and silt, becoming partially protected from complete decay by the lack of oxygen.
The generated oil is initially trapped within the micropores of the source rock, bonded to the mineral matrix by strong molecular forces. When these organisms—primarily algae, plankton, and other microorganisms—die, their remains sink to the seabed or lake floor.
Burial Compaction Heat Driving Oil Generation Mechanism
Common reservoir rocks are sandstone and limestone. Burial and Initial Transformation Over time, the accumulation of new sediment layers continuously buries this organic-rich material.
More About How are oils formed
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