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East Breaks geochemistry (view source)
Revision as of 20:02, 30 January 2014
, 20:02, 30 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 = Sedimentary basin analysis
| frompg = 4-1
| topg = 4-123
| author = John M. Armentrout
| link = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
Two oil samples ''(Glob alt ='' GA-3 and ''Hyal B ='' HB-2) from two different reservoirs in the East Breaks 160-161 field provide data for [[modeling]] the history of hydrocarbon generation and [[migration]] within this minibasin. Dow et al.<ref name=ch04r29>Dow, W., G., Yukler, M., A., Senftle, J., T., Kennicutt, M., C., IIArmentrout, J., M., 1990, Miocene oil source beds in the East Breaks basin, Flex-Trend, offshore Texas: Proceedings, Gulf Coast Section SEPM 9th Annual Research conference, p. 139–150.</ref> report that the East Breaks oils are biodegraded and mixed lower molecular weight, thermally mature oil. The C<sub>10</sub> through C<sub>30</sub> alkanes of the GA-3 oil are better preserved than those of the HB-2 oil. This is demonstrated by the higher peaks of C<sub>10</sub> through C<sub>30</sub> alkanes on the [[gas chromatogram]]s below, suggesting that the stratigraphically deeper GA-3 oil is less degraded and slightly more mature than the stratigraphically shallower HB-2 oil. Neither oil exhibits evidence of evaporative fractionation reported by Thompson<ref name=ch04r95>Thompson, K., F., M., 1987, Fractionated aromatic petroleums and the generation of gas-condensates: Organic Geochemistry, vol. 11, p. 573–590., 10., 1016/0146-6380(87)90011-8</ref> in over 75% of Gulf Coast Tertiary oils.
==Oil preservation pattern==
The oil preservation pattern is attributed to the history of generation, expulsion, secondary migration, and accumulation.<ref name=ch04r29 /> The better preserved C<sub>10</sub> to C<sub>30</sub> alkanes in the GA-3 oil occur where the reservoir temperature is about [[temperature::160°F]] ([[temperature::71°C]]). The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about [[temperature::130°F]] (Figure 4-52). Microbial activity responsible for biodegradation occurs at temperatures below [[temperature::140°F]] ([[temperature::60°C]]). The earliest migration fluids would have been the least mature and potentially most biodegraded due to the shallow level of accumulation. With increasing burial of the [[source rock]], more mature oil and condensate would have been generated and better preserved in deeper reservoirs below the depth of microbial activity. These observations suggest sequential expulsion and migration of progressively more mature products as the source(s) passed through the oil window. Alternative interpretations are offered in Dow et al.<ref name=ch04r29 />).
The figure below shows whole oil chromatograms of crude oils from two reservoirs in the East Breaks 160-161 field. Oil 1 is from the HB-2 reservoir; oil 2 is from the ''Glob alt'' GA-3 reservoir. Both are interpreted as biodegraded and mixed with fresh oil, suggesting multiple pulses of accumulation.
[[file:sedimentary-basin-analysis_fig4-51.png|thumb|{{figure number|4-51}}. Copyright: Dow et al. (1990); courtesy Gulf Coast SEPM.]]
[[file:sedimentary-basin-analysis_fig4-52.png|thumb|{{figure number|4-52}}After Dow et al.<ref name=ch04r29 />). Copyright: Gulf Coast SEPM.]]
==See also==
* [[East breaks petroleum system processes]]
* [[Trap formation]]
* [[Hydrocarbon generation model]]
* [[Hydrocarbon migration model]]
* [[Hydrocarbon accumulation model]]
* [[Critical moment (or Interval)]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.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:Sedimentary basin analysis]]
| 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 = Sedimentary basin analysis
| frompg = 4-1
| topg = 4-123
| author = John M. Armentrout
| link = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm
| pdf =
| store = http://store.aapg.org/detail.aspx?id=545
| isbn = 0-89181-602-X
}}
Two oil samples ''(Glob alt ='' GA-3 and ''Hyal B ='' HB-2) from two different reservoirs in the East Breaks 160-161 field provide data for [[modeling]] the history of hydrocarbon generation and [[migration]] within this minibasin. Dow et al.<ref name=ch04r29>Dow, W., G., Yukler, M., A., Senftle, J., T., Kennicutt, M., C., IIArmentrout, J., M., 1990, Miocene oil source beds in the East Breaks basin, Flex-Trend, offshore Texas: Proceedings, Gulf Coast Section SEPM 9th Annual Research conference, p. 139–150.</ref> report that the East Breaks oils are biodegraded and mixed lower molecular weight, thermally mature oil. The C<sub>10</sub> through C<sub>30</sub> alkanes of the GA-3 oil are better preserved than those of the HB-2 oil. This is demonstrated by the higher peaks of C<sub>10</sub> through C<sub>30</sub> alkanes on the [[gas chromatogram]]s below, suggesting that the stratigraphically deeper GA-3 oil is less degraded and slightly more mature than the stratigraphically shallower HB-2 oil. Neither oil exhibits evidence of evaporative fractionation reported by Thompson<ref name=ch04r95>Thompson, K., F., M., 1987, Fractionated aromatic petroleums and the generation of gas-condensates: Organic Geochemistry, vol. 11, p. 573–590., 10., 1016/0146-6380(87)90011-8</ref> in over 75% of Gulf Coast Tertiary oils.
==Oil preservation pattern==
The oil preservation pattern is attributed to the history of generation, expulsion, secondary migration, and accumulation.<ref name=ch04r29 /> The better preserved C<sub>10</sub> to C<sub>30</sub> alkanes in the GA-3 oil occur where the reservoir temperature is about [[temperature::160°F]] ([[temperature::71°C]]). The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about [[temperature::130°F]] (Figure 4-52). Microbial activity responsible for biodegradation occurs at temperatures below [[temperature::140°F]] ([[temperature::60°C]]). The earliest migration fluids would have been the least mature and potentially most biodegraded due to the shallow level of accumulation. With increasing burial of the [[source rock]], more mature oil and condensate would have been generated and better preserved in deeper reservoirs below the depth of microbial activity. These observations suggest sequential expulsion and migration of progressively more mature products as the source(s) passed through the oil window. Alternative interpretations are offered in Dow et al.<ref name=ch04r29 />).
The figure below shows whole oil chromatograms of crude oils from two reservoirs in the East Breaks 160-161 field. Oil 1 is from the HB-2 reservoir; oil 2 is from the ''Glob alt'' GA-3 reservoir. Both are interpreted as biodegraded and mixed with fresh oil, suggesting multiple pulses of accumulation.
[[file:sedimentary-basin-analysis_fig4-51.png|thumb|{{figure number|4-51}}. Copyright: Dow et al. (1990); courtesy Gulf Coast SEPM.]]
[[file:sedimentary-basin-analysis_fig4-52.png|thumb|{{figure number|4-52}}After Dow et al.<ref name=ch04r29 />). Copyright: Gulf Coast SEPM.]]
==See also==
* [[East breaks petroleum system processes]]
* [[Trap formation]]
* [[Hydrocarbon generation model]]
* [[Hydrocarbon migration model]]
* [[Hydrocarbon accumulation model]]
* [[Critical moment (or Interval)]]
==References==
{{reflist}}
==External links==
{{search}}
* [http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.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:Sedimentary basin analysis]]