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'''Migration''' of [[hydrocarbon]]s is a little-understood but critical process of the [[petroleum system]]. This chapter attempts to address the following questions:

'''Migration''' of [[hydrocarbon]]s is a little-understood but critical process of the [[petroleum system]]. The short definition is: Movement of petroleum from source rock toward a reservoir or seep. [[Primary migration]] is expulsion of petroleum from fine-grained source rock, while [[secondary migration]] moves petroleum through a coarse-grained carrier bed or fault to a reservoir or seep. [[Tertiary migration]] occurs when petroleum moves from one trap to another or to a seep.<ref name=Petersetal_2012>Peters, Kenneth E., David J. Curry, and Marek Kacewicz, 2012, [http://archives.datapages.com/data/specpubs/hedberg4/INTRODUCTION/INTRODUCTION.HTM An overview of basin and petroleum system modeling: Definitions and concepts], ''in'' Peters, Kenneth E., David J. Curry, and Marek Kacewicz, eds., Basin modeling: New horizons in research and applications: [http://store.aapg.org/detail.aspx?id=1106 AAPG Hedberg Series no. 4], p. 1-16.</ref>

 

The following questions are vital for understanding the complications of the process:

* How does oil escape from the [[source rock]]?

* How does oil escape from the [[source rock]]?

* Does oil migrate out of the [[trap]]?

* Does oil migrate out of the [[trap]]?

* Why are there marked differences in [[Wikipedia:API gravity|oil gravity]], wax content, and sulfur content in lateral and stratigraphically successive sands?

* Why are there marked differences in [[API gravity|oil gravity]], wax content, and sulfur content in [[lateral]] and stratigraphically successive sands?

* Why are there differences in water salinity for multiple sands in one [[structural trap system|structural trap]]?

* Why are there differences in water salinity for multiple sands in one [[structural trap system|structural trap]]?

* What is the role of [[fault]]s in transporting and trapping hydrocarbons?

* What is the role of [[fault]]s in transporting and trapping hydrocarbons?

==Chemistry of migrated hydrocarbons==

==Chemistry of migrated hydrocarbons==

Detailed chemical correlations made of [[reservoir]]ed [[hydrocarbon]]s with source rocks strongly indicate that the migration process does not significantly affect the overall geochemistry of the migrated hydrocarbons. However, general differences exist between the chemical composition of oils and the source rocks to which they are chemically correlated. These differences must be explained.

Detailed chemical correlations made of [[reservoir]]ed [[hydrocarbon]]s with source rocks strongly indicate that the migration process does not significantly affect the overall [[geochemistry]] of the migrated hydrocarbons. However, general differences exist between the chemical composition of oils and the source rocks to which they are chemically correlated. These differences must be explained.

==How we observe migration==

==How we observe migration==

* [[Migration by solution in water]]

* [[Migration by solution in water]]

* [[Migration by separate phase]]

* [[Migration by separate phase]]

[[Category:Critical elements of the petroleum system]][[Category:Migration of petroleum]]

[[Category:Critical elements of the petroleum system]][[Category:Migration of petroleum]]