Catagenesis is a term used in petroleum geology to describe the cracking process which results in the conversion of organic kerogens into hydrocarbons.

This chemical reaction is believed to be a time, temperature and pressure dependent process which creates liquid and/or gaseous hydrocarbon Hc from primary kerogen X and can be summarised using the formula:

where X₀ is the initial kerogen concentration and X(t) is the kerogen concentration at time t.

It is generally held that the dependence on pressure is negligible, such that the process of catagenesis can be given as a first-order differential equation:

where X is the reactant (kerogen) and κ is the reaction-rate constant which introduces the temperature-dependence via the Arrhenius equation.

Catagenesis is also retrogressive evolution. Contrast with anagenesis.

See also

• diagenesis
• fossil fuels