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Line 18: − + − − [[file:sedimentary-basin-analysis_fig4-51.png|thumb|{{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.]]
→Oil preservation pattern
==Oil preservation pattern==
==Oil preservation pattern==
[[file:sedimentary-basin-analysis_fig4-52.png|thumb|{{figure number|1}}The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about 130°F. After Dow et al.<ref name=ch04r29 /> Copyright: Gulf Coast SEPM.]]
[[file:sedimentary-basin-analysis_fig4-52.png|thumb|top|{{figure number|1}}The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about 130°F. After Dow et al.<ref name=ch04r29 /> Copyright: Gulf Coast SEPM.]] [[file:sedimentary-basin-analysis_fig4-51.png|thumb|top|{{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.]]
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]] ([[:file:sedimentary-basin-analysis_fig4-52.png|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.<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°F]] ([[temperature::71°C]]). The more poorly preserved alkanes in the HB-2 oil occur where the reservoir temperature is about [[temperature::130°F]] ([[:file:sedimentary-basin-analysis_fig4-52.png|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.<ref name=ch04r29 />
[[: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.
[[: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.