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Earth and Space Sciences · Glossary

What is Maturation; oil window; gas window?

Also known as: maturation · oil window · gas window

Definition 18.3 High School Earth and Space Sciences · Chapter 18 — The Geology of Coal, Oil and Gas

The maturation of a source rock is the transformation of its kerogen into oil and gas as it is buried and heated. The oil window is the range of temperature, from about 60 to 120∘C120{}^{\circ}\mathrm{C}, in which the kerogen mostly forms oil. Beyond about 120∘C120{}^{\circ}\mathrm{C}, in the gas window, it forms mostly methane.

Left: burial history of the Merrow Basin, an invented basin (computed model, compaction ignored). Each line follows one layer through time, from the day it was laid down at the surface; the thick line is the source rock, laid down 165 million years ago. With the surface at 20 C and a gradient of 30 C per kilometre, the oil window is the band between 1.3 and 3.3\, km. The dots mark when the source rock entered it and when it left it, for the gas window. Right: depth of the top and the base of the oil window against the geothermal gradient (surface at 20 C).
Left: burial history of the Merrow Basin, an invented basin (computed model, compaction ignored). Each line follows one layer through time, from the day it was laid down at the surface; the thick line is the source rock, laid down 165 million years ago. With the surface at 20∘C20{}^{\circ}\mathrm{C} and a gradient of 30∘C30{}^{\circ}\mathrm{C} per kilometre, the oil window is the band between 1.31.3 and 3.3 km3.3\,\mathrm{km}. The dots mark when the source rock entered it and when it left it, for the gas window. Right: depth of the top and the base of the oil window against the geothermal gradient (surface at 20∘C20{}^{\circ}\mathrm{C}).
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