1,705
edits
Changes
Jump to navigation
Jump to search
Primary migration and compositional changes (view source)
Revision as of 14:33, 24 January 2014
, 14:33, 24 January 2014Initial import
{{publication
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Critical elements of the petroleum system
| chapter = Migration of petroleum
| frompg = 7-1
| topg = 7-38
| author = Martin D. Matthews
| link = http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The composition of hydrocarbons expelled from a [[source rock]] is a primary control on the composition of reservoired hydrocarbons. In general, the larger-molecular-weight compounds are preferentially retained in the source rock while the smaller compounds are expelled.
==Factors favoring oil expulsion==
The following factors favor oil expulsion from a source rock:
* Type I or 2 kerogen
* Sufficient time in the oil window
* High levels of TOC
* Concentration of organic matter in lamina
* Low-capillary-pressure conduits
==Factors favoring gas expulsion==
Five factors favor gas expulsion from a source rock:
* Type 3 kerogen
* Rapid burial through the oil window
* Low TOC
* Dissemination of organic matter
* High-capillary-pressure conduits
==Composition of early vs. later generation==
Early generation concentrates light products into large pores and fracture networks. Thus, the oil expelled is lighter in composition than the oil retained. However, as maturity continues, the difference between these two disappears and oil–source correlation improves.
==Compositional changes and correlation==
Expulsion favors light compounds over heavy compounds and saturated hydrocarbons over aromatics. This is due to molecular filtering and adsorption–desorption phenomena, particularly during the early stages. However, because significant quantities of hydrocarbons are retained in the large and medium pore systems within the source rock, the correlation of reservoired oil with its respective source rock is not significantly affected. The effect of continued [[maturation]] of the source rock after expulsion is a more significant impediment to correlation.
==See also==
* [[Changes in hydocarbon composition during migration]]
* [[Compositional changes during postprimary migration]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Critical elements of the petroleum system]]
[[Category:Migration of petroleum]]
| image = exploring-for-oil-and-gas-traps.png
| width = 120px
| series = Treatise in Petroleum Geology
| title = Exploring for Oil and Gas Traps
| part = Critical elements of the petroleum system
| chapter = Migration of petroleum
| frompg = 7-1
| topg = 7-38
| author = Martin D. Matthews
| link = http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
The composition of hydrocarbons expelled from a [[source rock]] is a primary control on the composition of reservoired hydrocarbons. In general, the larger-molecular-weight compounds are preferentially retained in the source rock while the smaller compounds are expelled.
==Factors favoring oil expulsion==
The following factors favor oil expulsion from a source rock:
* Type I or 2 kerogen
* Sufficient time in the oil window
* High levels of TOC
* Concentration of organic matter in lamina
* Low-capillary-pressure conduits
==Factors favoring gas expulsion==
Five factors favor gas expulsion from a source rock:
* Type 3 kerogen
* Rapid burial through the oil window
* Low TOC
* Dissemination of organic matter
* High-capillary-pressure conduits
==Composition of early vs. later generation==
Early generation concentrates light products into large pores and fracture networks. Thus, the oil expelled is lighter in composition than the oil retained. However, as maturity continues, the difference between these two disappears and oil–source correlation improves.
==Compositional changes and correlation==
Expulsion favors light compounds over heavy compounds and saturated hydrocarbons over aromatics. This is due to molecular filtering and adsorption–desorption phenomena, particularly during the early stages. However, because significant quantities of hydrocarbons are retained in the large and medium pore systems within the source rock, the correlation of reservoired oil with its respective source rock is not significantly affected. The effect of continued [[maturation]] of the source rock after expulsion is a more significant impediment to correlation.
==See also==
* [[Changes in hydocarbon composition during migration]]
* [[Compositional changes during postprimary migration]]
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch07/ch07.htm Original content in Datapages]
* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]
[[Category:Critical elements of the petroleum system]]
[[Category:Migration of petroleum]]