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What conditions create the oil window where crude oil forms?
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petroleum
Liquid petroleum (crude oil)—which is refined into gasoline, diesel, heating fuels, asphalt, plastics, and other useful chemical compounds—is often extracted from the ground using a series of drills and pumps.
The oil window refers to the specific subsurface environment where kerogen undergoes thermal degradation and cracking to generate crude oil.1
This process occurs under the following conditions:
- Depth: Hydrocarbon generation typically takes place at depths ranging from approximately 760 to 4,880 metres (2,500 to 16,000 feet).1
- Temperature: The required temperature range is between 65 °C and 150 °C (150 °F and 300 °F).1
- Geologic Factors: The window is influenced by the geothermal gradient; in areas with higher gradients, the oil window may occur at shallower depths but will be narrower.1
Within this environment, the mild heating of kerogen over long periods causes the release of hydrocarbon chains, which eventually form the complex mixtures found in petroleum. Maximum generation generally occurs between 2,000 and 2,900 metres. If temperatures exceed these levels—typically below 4,800 metres—crude oil is no longer stable, and the primary product becomes dry thermal methane gas.1