Changes

[[file:oiloil-and-oilsource-rock-correlations_fig8-20.png|400px|thumb|{{figure number|16}}(left) Gas chromatograms of three oils from a common source in central Myanmar. A waxy oil (top) is sequentially converted into an extremely biodegraded remnant oil (bottom). (right) Whole-oil gas chromatograms of three oils from the offshore Mackenzie Delta, northwestern Canada, showing a modest decrease in the pristane–phytane ratio, apparently as the result of minor biodegradation. From Curiale et al.;<ref name=ch08r12>Curiale, J., A., 1994, [http://archives.datapages.com/data/specpubs/methodo2/data/a077/a077/0001/0250/0251.htm Correlation of oils and source rocks—a conceptual and historical perspective], in Magoon, L., B., Dow, W., G., eds., The [[Petroleum system]]—From Source to Trap: [http://store.aapg.org/detail.aspx?id=1022 AAPG Memoir 60], p. 251–260.</ref> and Curiale<ref name=ch08r9>Curiale, J., A., 1991, The petroleum geochemistry of Canadian Beaufort Tertiary “non-marine” oils: Chemical Geology, vol. 93, p. 21–45., 10., 1016/0009-2541(91)90062-V</ref> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-20.png|400px|thumb|{{figure number|16}}(left) Gas chromatograms of three oils from a common source in central Myanmar. A waxy oil (top) is sequentially converted into an extremely biodegraded remnant oil (bottom). (right) Whole-oil gas chromatograms of three oils from the offshore Mackenzie Delta, northwestern Canada, showing a modest decrease in the pristane–phytane ratio, apparently as the result of minor biodegradation. From Curiale et al.;<ref name=ch08r12>Curiale, J., A., 1994, [http://archives.datapages.com/data/specpubs/methodo2/data/a077/a077/0001/0250/0251.htm Correlation of oils and source rocks—a conceptual and historical perspective], in Magoon, L., B., Dow, W., G., eds., The [[Petroleum system]]—From Source to Trap: [http://store.aapg.org/detail.aspx?id=1022 AAPG Memoir 60], p. 251–260.</ref> and Curiale<ref name=ch08r9>Curiale, J., A., 1991, The petroleum geochemistry of Canadian Beaufort Tertiary “non-marine” oils: Chemical Geology, vol. 93, p. 21–45., 10., 1016/0009-2541(91)90062-V</ref> reprinted with permission from Elsevier.]]

Biodegradation can severely alter gas chromatograms. In the earliest stages of biodegradation, ''n''-alkanes are removed selectively, leading to significant loss of information.

[ http://www.oiltracers.com/services/exploration-geochemistry/oil-biodegradation.aspx Biodegradation] can severely alter gas chromatograms. In the earliest stages of biodegradation, [[Wikipedia:Alkane#Linear_alkanes|''n''-alkanes]] are removed selectively, leading to significant loss of information.

===Examples of biodegradation===

===Examples of biodegradation===

[[:file:oiloil-and-oilsource-rock-correlations_fig8-20.png|Figure 16]] (left) shows gas chromatograms of three oils from a common source in central Myanmar. A waxy oil (top) is sequentially converted into an extremely biodegraded remnant oil (bottom). The API gravity of the oil decreases and sulfur content increases substantially with increasing biodegradation.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-20.png|Figure 16]] (left) shows gas chromatograms of three oils from a common source in central Myanmar. A waxy oil (top) is sequentially converted into an extremely biodegraded remnant oil (bottom). The [[http://wiki.aapg.org/Petroleum_reservoir_fluid_properties#API_specific_gravity|API gravity]] of the oil decreases and sulfur content increases substantially with increasing biodegradation.

Pristane–phytane ratios may also be affected slightly at low stages of biodegradation. At moderate levels these compounds are removed completely (left figure). The right figure below shows whole-oil gas chromatograms of three oils from the offshore Mackenzie Delta, northwestern Canada, showing a modest decrease in the pristane–phytane ratio, apparently as the result of minor biodegradation.

[[Pristane-phytane ratio]]s may also be affected slightly at low stages of biodegradation. At moderate levels these compounds are removed completely (left figure). The right figure below shows whole-oil gas chromatograms of three oils from the offshore [[Mackenzie Delta]], northwestern Canada, showing a modest decrease in the pristane-phytane ratio, apparently as the result of minor biodegradation.

==See also==

==See also==