Changes

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The relative amounts of C₂₇, C₂₈ and C₂₉ steranes in oils are controlled by the types of photosynthetic organisms that contributed to the organic matter. A dominance of C₂₇ steranes is almost always associated with marine organisms. Most nonmarine organic matter has a dominance of the C₂₉ sterane precursors, but C₂₉ steranes can dominate in marine systems as well. The abundance of C₂₈ steranes in marine systems may depend primarily on geologic age<ref name=ch08r16>Grantham, P. J., and L. L. Wakefield, 1988, Variations in the sterane carbon number distributions of marine [[source rock]] derived crude oils through geological time: Organic Geochemistry, vol. 12, p. 61–73, DOI: 10.1016/0146-6380(88)90115-5.</ref> but this idea is controversial. In nonmarine systems, there is no proposed relationship between C₂₈ sterane abundance and age. C₃₀ steranes (''n''-propylcholestanes) are usually less abundant than the other regular steranes and occur only in samples deposited where marine organisms lived.<ref name=ch08r32>Moldowan, J. M., W. K. Seifert, and E. J. Gallegos, 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0008/1250/1255.htm Relationship between petroleum composition and depositional environment of petroleum source rocks]: AAPG Bulletin, vol. 69, p. 1255–1268.</ref>

The relative amounts of C₂₇, C₂₈ and C₂₉ steranes in oils are controlled by the types of photosynthetic organisms that contributed to the organic matter. A dominance of C₂₇ steranes is almost always associated with marine organisms. Most nonmarine organic matter has a dominance of the C₂₉ sterane precursors, but C₂₉ steranes can dominate in marine systems as well. The abundance of C₂₈ steranes in marine systems may depend primarily on geologic age<ref name=ch08r16>Grantham, P. J., and L. L. Wakefield, 1988, Variations in the sterane carbon number distributions of marine [[source rock]] derived [[crude oil]]s through geological time: Organic Geochemistry, vol. 12, p. 61–73, DOI: 10.1016/0146-6380(88)90115-5.</ref> but this idea is controversial. In nonmarine systems, there is no proposed relationship between C₂₈ sterane abundance and age. C₃₀ steranes (''n''-propylcholestanes) are usually less abundant than the other regular steranes and occur only in samples deposited where marine organisms lived.<ref name=ch08r32>Moldowan, J. M., W. K. Seifert, and E. J. Gallegos, 1985, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0069/0008/1250/1255.htm Relationship between petroleum composition and depositional environment of petroleum source rocks]: AAPG Bulletin, vol. 69, p. 1255–1268.</ref>

[[:file:oiloil-and-oilsource-rock-correlations_fig8-23.png|Figure 1]] shows m/z 217 mass fragmentograms from two oils showing quite different distributions of regular steranes. The top example is dominated by C₂₉ steranes with only moderate amounts of C₂₇ and C₂₈. The bottom sample, in contrast, shows similar amounts of all three homologs plus moderate amounts of the C₃₀ steranes (four unlabeled peaks to the far right).

[[:file:oiloil-and-oilsource-rock-correlations_fig8-23.png|Figure 1]] shows m/z 217 mass fragmentograms from two oils showing quite different distributions of regular steranes. The top example is dominated by C₂₉ steranes with only moderate amounts of C₂₇ and C₂₈. The bottom sample, in contrast, shows similar amounts of all three homologs plus moderate amounts of the C₃₀ steranes (four unlabeled peaks to the far right).

==Irregular homohopanes==

==Irregular homohopanes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-27.png|thumb|left|200px|{{figure number|5}}m/z 191 mass chromatograms for two sediment extracts from the Brac-1 well (Croatia) showing irregular homohopane distributions [relative enhancement of the C₃₅ species (left) and C₃₄ species. From Moldowan et al.;<ref name=ch08r33>Moldowan, J., M., Lee, C., Y., Sundararaman, P., Salvatori, T., Alajbeg, A., Gjukic, B., Demaison, G., J., Slougue, N.-E., Watt, D., S., 1992, Source correlation and maturity assessment of select oils and rocks from the central Adriatic Basin (Italy and Yugoslavia), in Moldowan, J., M., Albrecht, P., Philp, R., P., eds., Biological markers in sediments and petroleum: Englewood Cliffs, New Jersey, Prentice-Hall, 411 p.</ref> reprinted with permission from Prentice-Hall.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-27.png|thumb|left|200px|{{figure number|5}}m/z 191 mass chromatograms for two sediment extracts from the Brac-1 well (Croatia) showing irregular homohopane distributions [relative enhancement of the C₃₅ species (left) and C₃₄ species. From Moldowan et al.;<ref name=ch08r33>Moldowan, J. M., C. Y. Lee, P. Sundararaman, T. Salvatori, A. Alajbeg, B. Gjukic, G. J. Demaison, N.-E. Slougue, and D. S. Watt, 1992, Source correlation and maturity assessment of select oils and rocks from the central Adriatic Basin (Italy and Yugoslavia), in J. M. Moldowan, P. Albrecht, and R. P. Philp, eds., Biological markers in sediments and petroleum: Englewood Cliffs, New Jersey, Prentice-Hall, 411 p.</ref> reprinted with permission from Prentice-Hall.]]

Irregular distributions of the C₃₂–C₃₅ homohopanes are associated with carbonates<ref name=ch08r59 /> and/or more reducing conditions.<ref name=ch08r39 /> Unusually large amounts of the C₃₁ homohopanes are sometimes associated with coals and coaly material.<ref name=ch08r59 />

Irregular distributions of the C₃₂–C₃₅ homohopanes are associated with carbonates<ref name=ch08r59 /> and/or more reducing conditions.<ref name=ch08r39 /> Unusually large amounts of the C₃₁ homohopanes are sometimes associated with coals and coaly material.<ref name=ch08r59 />

==Gammacerane==

==Gammacerane==

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oiloil-and-oilsource-rock-correlations_fig8-28.png|{{figure number|6}}Gammacerane in the m/z 191 mass chromatograms of two genetically related oils from southern Sicily. From Ocampo et al.;<ref name=ch08r35>Ocampo, R., Riva, A., Trendel, J., M., Riolo, J., Callot, H., J., Albrecht, P., 1993, Petroporphyrins as biomarkers in oil-oil and oil-source rock correlations: Energy & Fuels, vol. 7, p. 191–193, DOI: 10.1021/ef00038a005</ref> reprinted with permission from American Chemical Society.

oiloil-and-oilsource-rock-correlations_fig8-28.png|{{figure number|6}}Gammacerane in the m/z 191 mass chromatograms of two genetically related oils from southern Sicily. From Ocampo et al.;<ref name=ch08r35>Ocampo, R., A. Riva, J. M. Trendel, J. Riolo, H. J. Callot, and P. Albrecht, 1993, Petroporphyrins as biomarkers in oil-oil and oil-source rock correlations: Energy & Fuels, vol. 7, p. 191–193, DOI: 10.1021/ef00038a005</ref> reprinted with permission from American Chemical Society.

oiloil-and-oilsource-rock-correlations_fig8-29.png|{{figure number|7}}Samples with gammacerane, but in this case gammacerane essentially coelutes with the C₃₁-22R epimer. From Mattavelli and Novelli;<ref name=ch08r29>Mattavelli, L., Novelli, L., 1990, Geochemistry and habitat of the oils in Italy: AAPG Bulletin, vol. 74, p. 1623–1639.</ref> reprinted with permission from AAPG.

oiloil-and-oilsource-rock-correlations_fig8-29.png|{{figure number|7}}Samples with gammacerane, but in this case gammacerane essentially coelutes with the C₃₁-22R epimer. From Mattavelli and Novelli;<ref name=ch08r29>Mattavelli, L., and L. Novelli, 1990, Geochemistry and habitat of the oils in Italy: AAPG Bulletin, vol. 74, p. 1623–1639.</ref> reprinted with permission from AAPG.

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==Oleananes==

==Oleananes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-30.png|200px|thumb|{{figure number|8}}Three mass chromatograms (m/z 191.18, 177.16, and 217.20, from top to bottom) for an oil from central Myanmar. From Curiale<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> reprinted with permission from AAPG.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-30.png|200px|thumb|{{figure number|8}}Three mass chromatograms (m/z 191.18, 177.16, and 217.20, from top to bottom) for an oil from central Myanmar. From Curiale<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 L. B. Magoon, and W. G. Dow, eds., The Petroleum system—From Source to Trap: [http://store.aapg.org/detail.aspx?id=1022 AAPG Memoir 60], p. 251–260.</ref> reprinted with permission from AAPG.]]

Oleanane (two major isomers exist) originates from terrestrial flowering plants of Late Cretaceous or, more commonly, [[Tertiary]] age and as such is very valuable in correlation problems when deciding whether an oil comes from a source rock that is young or old.<ref name=ch08r45>Riva, A., Caccialanza, P., G., Quagliaroli, F., 1988, Recognition of 18β(H)-oleanane in several crudes and Cainozoic-Upper Cretaceous sediments. Definition of a new maturity parameter: Organic Geochemistry, vol. 13, p. 671–675, DOI: 10.1016/0146-6380(88)90088-5.</ref>

Oleanane (two major isomers exist) originates from terrestrial flowering plants of Late Cretaceous or, more commonly, [[Tertiary]] age and as such is very valuable in correlation problems when deciding whether an oil comes from a source rock that is young or old.<ref name=ch08r45>Riva, A., P. G. Caccialanza, and F. Quagliaroli, 1988, Recognition of 18β(H)-oleanane in several crudes and Cainozoic-Upper Cretaceous sediments. Definition of a new maturity parameter: Organic Geochemistry, vol. 13, p. 671–675, DOI: 10.1016/0146-6380(88)90088-5.</ref>

[[:file:oiloil-and-oilsource-rock-correlations_fig8-30.png|Figure 8]] shows three mass chromatograms (m/z 191.18, 177.16, and 217.20, from top to bottom) for an oil from central Myanmar. The peak marked “o” is a combination of 18α(H) and 18β(H) oleanane. The tallest peak in the m/z 191 mass chromatogram is hopane, and the peaks indicated by solid dots are bicadinanes.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-30.png|Figure 8]] shows three mass chromatograms (m/z 191.18, 177.16, and 217.20, from top to bottom) for an oil from central Myanmar. The peak marked “o” is a combination of 18α(H) and 18β(H) oleanane. The tallest peak in the m/z 191 mass chromatogram is hopane, and the peaks indicated by solid dots are bicadinanes.

==Bicadinanes==

==Bicadinanes==

Bicadinanes are among the very few compounds that give substantial peaks in both the m/z 191 and 217 fragment ions. Bicadinane resins are derived from terrestrial plants that evolved in the [[Tertiary]]. The primary source plants, dipterocarps, spread slowly through Southeast Asia during the middle to late Tertiary. Bicadinanes are rare in other places and at other times, except from the Tertiary of New Zealand and Australia, where they probably originated from other species.<ref name=ch08r34>Murray, A., P., Summons, R., E., Bradshaw, J., Pawih, B., 1993, Cenozoic oil in Papua New Guinea—evidence from geochemical analysis of two newly discovered seeps, in Carman, G., J., Carman, Z., eds., Petroleum Exploration and Development in Papua New Guinea: Proceedings of the Second PNG Petroleum Convention, Australian Geological Survey, p. 489–498.</ref> Bicadinanes are often found together with oleanane.

Bicadinanes are among the very few compounds that give substantial peaks in both the m/z 191 and 217 fragment ions. Bicadinane resins are derived from terrestrial plants that evolved in the [[Tertiary]]. The primary source plants, dipterocarps, spread slowly through Southeast Asia during the middle to late Tertiary. Bicadinanes are rare in other places and at other times, except from the Tertiary of New Zealand and Australia, where they probably originated from other species.<ref name=ch08r34>Murray, A. P., R. E. Summons, J. Bradshaw, and B. Pawih, 1993, Cenozoic oil in Papua New Guinea—evidence from geochemical analysis of two newly discovered seeps, in G. J. Carman, and Z. Carman, eds., Petroleum Exploration and Development in Papua New Guinea: Proceedings of the Second PNG Petroleum Convention, Australian Geological Survey, p. 489–498.</ref> Bicadinanes are often found together with oleanane.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-30.png|Figure 8]] shows bicadinanes in an oil sample from Myanmar. Note that the bicadinane peaks (indicated by solid dots) appear in all three fragment ions.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-30.png|Figure 8]] shows bicadinanes in an oil sample from Myanmar. Note that the bicadinane peaks (indicated by solid dots) appear in all three fragment ions.

[[file:oiloil-and-oilsource-rock-correlations_fig8-31.png|left|200px|thumb|{{figure number|9}}m/z 191 mass chromatograms of three oils from the Cooper/Eromanga basin of Australia. From Philp and Gilbert;<ref name=ch08r42 /> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-31.png|left|200px|thumb|{{figure number|9}}m/z 191 mass chromatograms of three oils from the Cooper/Eromanga basin of Australia. From Philp and Gilbert;<ref name=ch08r42 /> reprinted with permission from Elsevier.]]

Two triterpanes, often called “C_z” and “C_x,” are also empirically associated with terrestrial organic matter, but their origin is unknown. They can be seen in [[:file:oiloil-and-oilsource-rock-correlations_fig8-26.png|Figure 4]]. C_z has also been called compound X<ref name=ch08r42>Philp, R., P., Gilbert, T., D., 1986, Biomarker distributions in oils predominantly derived from terrigenous source material, in Leythaeuser, D., Rullkötter, J., eds., Advances in Organic Geochemistry 1985: New York, Elsevier, p. 73–84.</ref> and has been shown to be a diahopane.<ref name=ch08r39 /> C_x is probably a neohopane. They often co-occur with other terrestrial markers, such as high C₂₉ steranes, oleanane, and bicadinanes, but they can also occur alone.

Two triterpanes, often called “C_z” and “C_x,” are also empirically associated with terrestrial organic matter, but their origin is unknown. They can be seen in [[:file:oiloil-and-oilsource-rock-correlations_fig8-26.png|Figure 4]]. C_z has also been called compound X<ref name=ch08r42>Philp, R. P., and T. D. Gilbert, 1986, Biomarker distributions in oils predominantly derived from terrigenous source material, in D. Leythaeuser, and J. Rullkötter, eds., Advances in Organic Geochemistry 1985: New York, Elsevier, p. 73–84.</ref> and has been shown to be a diahopane.<ref name=ch08r39 /> C_x is probably a neohopane. They often co-occur with other terrestrial markers, such as high C₂₉ steranes, oleanane, and bicadinanes, but they can also occur alone.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-31.png|Figure 9]] shows m/z 191 mass chromatograms of three oils from the Cooper/Eromanga basin of Australia. The highest relative concentrations of C_z and C_x occur in the oil that appears to have the lowest absolute concentration of other triterpanes (Karmona), as judged by the greatest amount of noise in the baseline. C_z and C_x (unlabelled but visible to the left of peak “b” in the Karmona sample) are probably more resistant to thermal destruction, and thus increase in relative concentration as other triterpanes are destroyed at high levels of maturity.<ref name=ch08r59 /> C_x often coelutes with T_m (peak “b” in this figure).

[[:file:oiloil-and-oilsource-rock-correlations_fig8-31.png|Figure 9]] shows m/z 191 mass chromatograms of three oils from the Cooper/Eromanga basin of Australia. The highest relative concentrations of C_z and C_x occur in the oil that appears to have the lowest absolute concentration of other triterpanes (Karmona), as judged by the greatest amount of noise in the baseline. C_z and C_x (unlabelled but visible to the left of peak “b” in the Karmona sample) are probably more resistant to thermal destruction, and thus increase in relative concentration as other triterpanes are destroyed at high levels of maturity.<ref name=ch08r59 /> C_x often coelutes with T_m (peak “b” in this figure).

==Diterpanes==

==Diterpanes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-34.png|thumb|{{figure number|12}}m/z 123 mass chromatograms of two oils from northeast China. From Huang et al.;<ref name=ch08r19>Huang, Y., Ansong, G., Jiamo, F., Guoying, S., Biqiang, Z., Yixian, C., Maofen, L., 1992, The investigation of characteristics of biomarker assemblages and their precursors in Damintun ultra-high wax oils and related source rocks: Organic Geochemistry, vol. 19, p. 29–39, DOI: 10.1016/0146-6380(92)90025-S.</ref> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-34.png|thumb|{{figure number|12}}m/z 123 mass chromatograms of two oils from northeast China. From Huang et al.;<ref name=ch08r19>Huang, Y., G. Ansong, F. Jiamo, S. Guoying, Z. Biqiang, C. Yixian, and L. Maofen, 1992, The investigation of characteristics of biomarker assemblages and their precursors in Damintun ultra-high wax oils and related source rocks: Organic Geochemistry, vol. 19, p. 29–39, DOI: 10.1016/0146-6380(92)90025-S.</ref> reprinted with permission from Elsevier.]]

Other diterpane and sesquiterpane distributions are also used for correlations. Most diterpanes originate from terrestrial resins, but microbial sources are also known.<ref name=ch08r39 /> Sesquiterpanes derive primarily from terrestrial plant resins. Most resin-derived compounds are of Tertiary or possibly Late Cretaceous age.

Other diterpane and sesquiterpane distributions are also used for correlations. Most diterpanes originate from terrestrial resins, but microbial sources are also known.<ref name=ch08r39 /> Sesquiterpanes derive primarily from terrestrial plant resins. Most resin-derived compounds are of Tertiary or possibly Late Cretaceous age.

[[file:oiloil-and-oilsource-rock-correlations_fig8-35.png|left|thumb|{{figure number|13}}Carotanes are sometimes so abundant that they can be analyzed using gas chromatography. Modified. Copyright: Peters and Moldowan (1993); courtesy Prentice-Hall.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-35.png|left|thumb|{{figure number|13}}Carotanes are sometimes so abundant that they can be analyzed using gas chromatography. Modified. Copyright: Peters and Moldowan (1993); courtesy Prentice-Hall.]]

Carotanes—hydrocarbons derived from photosynthetic organisms and associated with anoxic marine and lacustrine facies—are also used as oil–oil and oil–source rock correlation parameters. Peters et al.<ref name=ch08r40>Peters, K., E., Moldowan, J., M., Driscole, A., R., Demaison, G., J., 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0004/0450/0454.htm Origin of Beatrice oil by co-sourcing from Devonian and Middle Jurassic source rocks, Inner Moray Firth, UK]: AAPG Bulletin, vol. 73, p. 454–471.</ref> used the occurrence of β-carotane in Devonian rocks (of the U.K. offshore) to suggest a Devonian input to the source composition of the Beatrice oil. These compounds are particularly useful in hypersaline settings. Lacustrine and marine facies containing carotanes can often be distinguished by other indicators, such as the presence of 4-methylsteranes and pristane-phytane ratios less than 1.0 for lacustrine facies.

Carotanes—hydrocarbons derived from photosynthetic organisms and associated with anoxic marine and lacustrine facies—are also used as oil–oil and oil–source rock correlation parameters. Peters et al.<ref name=ch08r40>Peters, K. E., J. M. Moldowan, A. R. Driscole, and G. J. Demaison, 1989, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0004/0450/0454.htm Origin of Beatrice oil by co-sourcing from Devonian and Middle Jurassic source rocks, Inner Moray Firth, UK]: AAPG Bulletin, vol. 73, p. 454–471.</ref> used the occurrence of β-carotane in Devonian rocks (of the U.K. offshore) to suggest a Devonian input to the source composition of the Beatrice oil. These compounds are particularly useful in hypersaline settings. Lacustrine and marine facies containing carotanes can often be distinguished by other indicators, such as the presence of 4-methylsteranes and pristane-phytane ratios less than 1.0 for lacustrine facies.

Unfortunately many analyses overlook carotanes because these high-molecular-weight compounds elute very late on gas Chromatograph columns. To obtain this information, you may have to make special arrangements prior to analysis. Thus, the absence of carotanes in chromatograms may simply indicate that they were not looked for, rather than that they are truly absent.

Unfortunately many analyses overlook carotanes because these high-molecular-weight compounds elute very late on gas Chromatograph columns. To obtain this information, you may have to make special arrangements prior to analysis. Thus, the absence of carotanes in chromatograms may simply indicate that they were not looked for, rather than that they are truly absent.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-35.png|Figure 13]] shows that carotanes are sometimes so abundant that they can be analyzed using gas chromatography (More definitive identification and analysis of samples in which carotanes are less abundant can be done using GC/MS.) The gas chromatograms are of the Beatrice Field oil in the Moray Firth (U.K.) and of the extract of a Devonian rock believed to be one of the source contributors.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-35.png|Figure 13]] shows that carotanes are sometimes so abundant that they can be analyzed using [[gas chromatography]] (More definitive identification and analysis of samples in which carotanes are less abundant can be done using GC/MS.) The gas chromatograms are of the Beatrice Field oil in the Moray Firth (U.K.) and of the extract of a Devonian rock believed to be one of the source contributors.

==Summary of application of GC/MS to correlation studies==

==Summary of application of GC/MS to correlation studies==

[[Category:Oil–oil and oil–source rock correlations]]

[[Category:Oil–oil and oil–source rock correlations]]

[[Category:Geochemistry]]

[[Category:Geochemistry]]