Changes

  | part    = Critical elements of the petroleum system

  | part    = Critical elements of the petroleum system

  | chapter = Oil–oil and oil–source rock correlations

  | chapter = Oil–oil and oil–source rock correlations

  | frompg  = 8-1

  | frompg  = 8-33

  | topg    = 8-71

  | topg    = 8-44

  | author  = Douglas W. Waples, Joseph A. Curiale

  | author  = Douglas W. Waples, Joseph A. Curiale

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch08/ch08.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch08/ch08.htm

==Steranes==

==Steranes==

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>

 

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., Wakefield, L., L., 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., Seifert, W., K., Gallegos, E., J., 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).

[[:file:oiloil-and-oilsource-rock-correlations_fig8-24.png|Figure 2]] shows a ternary diagram, a convenient and common way of displaying basic data on sterane distributions. This example shows the relative proportions of the C₂₇, C₂₈, and C₂₉ regular steranes for several extracts from two distinct facies within the nonmarine Elko Formation (Eocene/Oligocene) of Nevada. The lignitic siltstones are dominated by terrestrial plant material, whereas the oil shales are made up of lacustrine algae.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-24.png|Figure 2]] shows a ternary diagram, a convenient and common way of displaying basic data on sterane distributions. This example shows the relative proportions of the C₂₇, C₂₈, and C₂₉ regular steranes for several extracts from two distinct facies within the nonmarine Elko Formation (Eocene/Oligocene) of Nevada. The lignitic siltstones are dominated by terrestrial plant material, whereas the [[oil shales]] are made up of lacustrine algae.

==4-methylsteranes==

==4-methylsteranes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-25.png|thumb|left|{{figure number|3}}Distribution of 4-methylsteranes in selected rock extracts. Modified from Summons et al.;<ref name=ch08r52>Summons, R., E., Thomas, J., Maxwell, J., R., Boreham, C., J., 1992, Secular and environmental constraints on the occurrence of dinosteranes in sediments: Geochimica et Cosmochimica Acta, vol. 56, p. 2437–2444, DOI: 10.1016/0016-7037(92)90200-3.</ref> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-25.png|thumb|200px|{{figure number|3}}Distribution of 4-methylsteranes in selected rock extracts. Modified from Summons et al.;<ref name=ch08r52>Summons, R. E., J. Thomas, J. R. Maxwell, and C. J. Boreham, 1992, Secular and environmental constraints on the occurrence of dinosteranes in sediments: Geochimica et Cosmochimica Acta, vol. 56, p. 2437–2444, DOI: 10.1016/0016-7037(92)90200-3.</ref> reprinted with permission from Elsevier.]]

MRM analysis is useful in distinguishing ''n''-propylcholestanes from 4-methylsteranes and in assigning identities to different types of 4-methylsteranes. This sophisticated GC/MS analysis method will probably become commonplace because of its specificity in oil–oil and oil–source rock correlation efforts.

MRM analysis is useful in distinguishing ''n''-propylcholestanes from 4-methylsteranes and in assigning identities to different types of 4-methylsteranes. This sophisticated GC/MS analysis method will probably become commonplace because of its specificity in oil–oil and oil–source rock correlation efforts.

==Hopanes==

==Hopanes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-26.png|thumb|{{figure number|4}}m/z 191 mass fragmentogram of an oil displaying the most common type of homohopane distribution.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-26.png|200px|thumb|{{figure number|4}}m/z 191 mass fragmentogram of an oil displaying the most common type of homohopane distribution.]]

Hopanes, which originate from bacteria, are the most abundant triterpanes. A distribution with a regular decrease of homohopanes from C₃₁ to C₃₅ is thought to be associated with clastic environments.<ref name=ch08r59>Waples, D., W., Machihara, T., 1991, Biomarkers for geologists: Tulsa, AAPG, 91 p.</ref> and/or more oxidizing conditions<ref name=ch08r39>Peters, K., E., Moldowan, J., M., 1993, The Biomarker Guide—Interpreting [[Molecular fossils]] in Petroleum and Ancient Sediments: Englewood Cliffs, New Jersey, Prentice-Hall, 363 p.</ref>

Hopanes, which originate from bacteria, are the most abundant triterpanes. A distribution with a regular decrease of homohopanes from C₃₁ to C₃₅ is thought to be associated with clastic environments.<ref name=ch08r59>Waples, D. W., and T. Machihara, 1991, Biomarkers for geologists: AAPG Methods in Exploration 9, 91 p.</ref> and/or more oxidizing conditions<ref name=ch08r39>Peters, K. E., and J. M. Moldowan, 1993, The Biomarker Guide—Interpreting [[Molecular fossils]] in Petroleum and Ancient Sediments: Englewood Cliffs, New Jersey, Prentice-Hall, 363 p.</ref>

[[:file:oiloil-and-oilsource-rock-correlations_fig8-26.png|Figure 4]] shows the m/z 191 mass fragmentogram of an oil displaying the most common type of homohopane distribution.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-26.png|Figure 4]] shows the m/z 191 mass fragmentogram of an oil displaying the most common type of homohopane distribution.

==Irregular homohopanes==

==Irregular homohopanes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-27.png|thumb|left|{{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 />

[[:file:oiloil-and-oilsource-rock-correlations_fig8-27.png|Figure 5]] shows 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 (right). We would expect the oils sourced from these sediments to show these same characteristics.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-27.png|Figure 5]] shows 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 (right). We would expect the oils sourced from these sediments to show these same characteristics.

==Gammacerane==

==Gammacerane==

[[file:oiloil-and-oilsource-rock-correlations_fig8-28.png|thumb|{{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.

In addition to the hopane family, several other types of triterpanes that are occasionally encountered can be very useful in correlations. Gammacerane is often found in sediments deposited under abnormal salinites, including lacustrine facies. Identification of gammacerane can be difficult, however, both because it is usually only a minor component and because it elutes at different places with different chromatographic columns.

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.

[[file:oiloil-and-oilsource-rock-correlations_fig8-29.png|thumb|left|{{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.]]

In addition to the hopane family, several other types of triterpanes that are occasionally encountered can be very useful in correlations. Gammacerane is often found in sediments deposited under abnormal salinites, including lacustrine facies. Identification of gammacerane can be difficult, however, both because it is usually only a minor component and because it [http://www.thefreedictionary.com/elution elutes] at different places with different chromatographic columns.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-28.png|Figure 6]] shows gammacerane in the m/z 191 mass chromatograms of two genetically related oils from southern Sicily. In this example, gammacerane elutes after the C₃₁ homohopanes. Note also the relative increase in the C₃₄ and C₃₅ homohopanes. The presence of gammacerane and the homohopane distribution suggest a strongly reducing, possibly carbonate or hypersaline depositional setting for the source rock of these oils.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-28.png|Figure 6]] shows gammacerane in the m/z 191 mass chromatograms of two genetically related oils from southern Sicily. In this example, gammacerane elutes after the C₃₁ homohopanes. Note also the relative increase in the C₃₄ and C₃₅ homohopanes. The presence of gammacerane and the homohopane distribution suggest a strongly reducing, possibly carbonate or hypersaline depositional setting for the source rock of these oils.

==Oleananes==

==Oleananes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-30.png|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.

==C_x and C_z triterpanes==

==C_x and C_z triterpanes==

[[file:oiloil-and-oilsource-rock-correlations_fig8-31.png|left|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).

==28,30-bisnorhopane==

==28,30-bisnorhopane==

[[file:oiloil-and-oilsource-rock-correlations_fig8-32.png|thumb|{{figure number|10}}m/z 191 mass fragmentogram of an oil with a high relative concentration of 28,30-bisnorhopane, eluting to the left of norhopane (C₂₉ hopane).]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-32.png|200px|thumb|{{figure number|10}}m/z 191 mass fragmentogram of an oil with a high relative concentration of 28,30-bisnorhopane, [http://www.thefreedictionary.com/elution eluting] to the left of norhopane (C₂₉ hopane).]]

Sometimes in great abundance, 28,30-bisnorhopane has been found in a few important source rocks and related oils (Monterey Formation, Kimmeridge Clay). It is probably of microbial origin. Because bisnorhopane is most common in sulfur-rich environments, its origin may have to do with bacteria that participate in the sulfur cycle. Denis Miiller (personal communication, 1994) notes that in the Monterey oils of southern California, bisnorhopane contents are proportional to sulfur contents.

Sometimes in great abundance, 28,30-bisnorhopane has been found in a few important source rocks and related oils (Monterey Formation, Kimmeridge Clay). It is probably of microbial origin. Because bisnorhopane is most common in sulfur-rich environments, its origin may have to do with bacteria that participate in the sulfur cycle. Denis Miiller (personal communication, 1994) notes that in the Monterey oils of southern California, bisnorhopane contents are proportional to sulfur contents.

==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==

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! This class of compound …

! This class of compound … || May indicate an origin of …

! May indicate an origin of …

|-

|-

| C₂₇ steranes

| C₂₇ steranes || Marine organisms (minor amounts occur in nonmarine organisms)

| Marine organisms (minor amounts occur in nonmarine organisms)

|-

|-

| C₂₉ steranes

| C₂₉ steranes || Marine or nonmarine organic matter

| Marine or nonmarine organic matter

|-

|-

| C₃₀ steranes

| C₃₀ steranes || Marine or lacustrine organisms

| Marine or lacustrine organisms

|-

|-

| Diasteranes

| Diasteranes || Clastic environment

| Clastic environment

|-

|-

| Hopanes

| Hopanes || Bacteria

| Bacteria

|-

|-

| Gammacerane

| Gammacerane || Abnormal salinites

| Abnormal salinites

|-

|-

| Oleanane

| Oleanane || Late Cretaceous or Tertiary terrestrial flowering plants

| Late Cretaceous or Tertiary terrestrial flowering plants

|-

|-

| Bicadinanes

| Bicadinanes || Tertiary terrestrial plants

| Tertiary terrestrial plants

|-

|-

| C_z and C_x triterpanes

| C_z and C_x triterpanes || Terrestrial organic matter or environment

| Terrestrial organic matter or environment

|-

|-

| 28,30-bisnorhopane

| 28,30-bisnorhopane || Microbes

| Microbes

|-

|-

| Tricyclic terpanes

| Tricyclic terpanes || Bacteria or ''Tasmanites''

| Bacteria or ''Tasmanites''

|-

|-

| Diterpanes

| Diterpanes || Terrestrial resins or microbes

| Terrestrial resins or microbes

|-

|-

| Sesquiterpanes

| Sesquiterpanes || Terrestrial plant resins

| Terrestrial plant resins

|-

|-

| Carotanes

| Carotanes || Anoxic marine or lacustrine environment

| Anoxic marine or lacustrine environment

|}

|}

==See also==

==See also==

* [[Molecular parameter data]]

* [[Molecular parameter data for oil–oil and oil–source rock correlations]]

* [[Data obtained by gas chromatography]]

* [[Gas chromatography: data obtained]]

* [[How is GC/MS done?]]

* [[Gas chromatography/mass spectrometry (GC/MS): procedures]]

* [[Examples of correlations using GC/MS]]

* [[Gas chromatography/mass spectrometry (GC/MS): examples of correlations]]

* [[Gas chromatography/mass spectrometry (GC/MS): limitations]]

* [[Gas chromatography/mass spectrometry (GC/MS): limitations]]

* [[High-performance liquid chromatography]]

* [[High-performance liquid chromatography]]

[[Category:Critical elements of the petroleum system]]  

[[Category:Critical elements of the petroleum system]]  

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

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