Changes

==Alteration processes==

==Alteration processes==

Processes responsible for altering the composition of hydrocarbons during migration include the following:

Processes responsible for altering the composition of [[hydrocarbon]]s during migration include the following:

* Water-washing—selective removal of the more water-soluble components

* Water-washing—selective removal of the more water-soluble components

* Adsorption—selective removal and retardation of hydrocarbon migration rate by mineral and kerogen particles

* Adsorption—selective removal and retardation of hydrocarbon migration rate by mineral and [http://www.thefreedictionary.com/kerogen kerogen] particles

* Phase partitioning—concentration of different hydrocarbon species into gaseous and liquid phases with changes in pressure and temperature

* Phase partitioning—concentration of different hydrocarbon species into gaseous and liquid phases with changes in pressure and temperature

* Mixing—by (1) including hydrocarbons from post-source-rock kerogen particles along the migration path; (2) mixing migration streams from two or more source rocks; or (3) precipitation of asphaltenes and other high-molecular-weight compounds by the addition of methane

* Mixing—by (1) including hydrocarbons from kerogen particles along the migration path; (2) mixing [[migration]] streams from two or more source rocks; or (3) precipitation of [http://petrowiki.org/Asphaltenes_and_waxes asphaltenes] and other high-molecular-weight compounds by the addition of [http://scifun.chem.wisc.edu/chemweek/methane/methane.html methane]

* Biodegradation—biologic alteration of the hydrocarbons

* Biodegradation—biologic alteration of the hydrocarbons