Difference between revisions of "East Breaks geochemistry"

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  | part    = Critical elements of the petroleum system
 
  | part    = Critical elements of the petroleum system
 
  | chapter = Sedimentary basin analysis
 
  | chapter = Sedimentary basin analysis
  | frompg  = 4-1
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  | frompg  = 4-97
  | topg    = 4-123
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  | topg    = 4-97
 
  | author  = John M. Armentrout
 
  | author  = John M. Armentrout
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm
 
  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm
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  | isbn    = 0-89181-602-X
 
  | isbn    = 0-89181-602-X
 
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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.
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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., M. A. Yukler, J. T. Senftle, M. C. Kennicutt, and J. M. Armentrout, 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 [[biodegradation|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==
 
==Oil preservation pattern==
 +
<gallery mode=packed heights=300px widths=300px>
 +
sedimentary-basin-analysis_fig4-52.png|{{figure number|1}}The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about 130&deg;F. After Dow et al.<ref name=ch04r29 /> Copyright: Gulf Coast SEPM.
 +
sedimentary-basin-analysis_fig4-51.png|{{figure number|2}}whole oil chromatograms of crude oils from two reservoirs in the East Breaks 160-161 field. Copyright: Dow et al.<ref name=ch04r29 /> Courtesy Gulf Coast SEPM.
 +
</gallery>
  
[[file:sedimentary-basin-analysis_fig4-52.png|thumb|{{figure number|1}}After Dow et al.<ref name=ch04r29 /> Copyright: Gulf Coast SEPM.]]
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The oil preservation pattern is attributed to the history of [[Petroleum generation|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&deg;F]] ([[temperature::71&deg;C]]). The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about [[temperature::130&deg;F]] ([[:file:sedimentary-basin-analysis_fig4-52.png|Figure 1]]). Microbial activity responsible for [[biodegradation]] occurs at temperatures below [[temperature::140&deg;F]] ([[temperature::60&deg;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 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&deg;F]] ([[temperature::71&deg;C]]). The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about [[temperature::130&deg;F]] ([[:file:sedimentary-basin-analysis_fig4-52.png|Figure 1]]). Microbial activity responsible for biodegradation occurs at temperatures below [[temperature::140&deg;F]] ([[temperature::60&deg;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 />
+
[[:file:sedimentary-basin-analysis_fig4-51.png|Figure 2]] shows whole oil chromatograms of [[crude oil]]s 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|2}}. Copyright: Dow et al.<ref name=ch04r29 /> Courtesy Gulf Coast SEPM.]]
 
 
 
[[:file:sedimentary-basin-analysis_fig4-51.png|Figure 2]] 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.
 
  
 
==See also==
 
==See also==
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[[Category:Sedimentary basin analysis]]
 
[[Category:Sedimentary basin analysis]]
 
[[Category:East Breaks]]
 
[[Category:East Breaks]]
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[[Category:Treatise Handbook 3]]

Latest revision as of 15:33, 23 March 2022

Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Critical elements of the petroleum system
Chapter Sedimentary basin analysis
Author John M. Armentrout
Link Web page
Store AAPG Store

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.[1] report that the East Breaks oils are biodegraded and mixed lower molecular weight, thermally mature oil. The C10 through C30 alkanes of the GA-3 oil are better preserved than those of the HB-2 oil. This is demonstrated by the higher peaks of C10 through C30 alkanes on the gas chromatograms 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[2] 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.[1] The better preserved C10 to C30 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 1). 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.[1]

Figure 2 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.

See also

References

  1. 1.0 1.1 1.2 1.3 1.4 Dow, W. G., M. A. Yukler, J. T. Senftle, M. C. Kennicutt, and J. M. Armentrout, 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.
  2. 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

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