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  = 8-15

  | topg    = 8-71

  | topg    = 8-16

  | 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

==Carbon isotope ratios==

==Carbon isotope ratios==

[[file:oiloil-and-oilsource-rock-correlations_fig8-3.png|300px|thumb|{{figure number|1}}Carbon isotope ratios for fractions of six oils comprising two families from the Zagros orogenic belt. The “Galimov” plot (left) and the Sofer diagram (right) show the δ¹³C values. From Bordenave and Burwood;<ref name=ch08r2>Bordenave, M., L., Burwood, R., 1990, [[Source rock]] distribution and [[maturation]] in the Zagros orogenic belt: provenance of the Asmari and Bangestan reservoir oil accumulations: Organic Geochemistry, vol. 16, p. 369–387., 10., 1016/0146-6380(90)90055-5</ref> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-3.png|300px|thumb|{{figure number|1}}Carbon isotope ratios for fractions of six oils comprising two families from the Zagros orogenic belt. The “Galimov” plot (left) and the Sofer diagram (right) show the δ¹³C values. From Bordenave and Burwood;<ref name=ch08r2>Bordenave, M. L., and R. Burwood, 1990, [[Source rock]] distribution and [[maturation]] in the Zagros orogenic belt: provenance of the Asmari and Bangestan reservoir oil accumulations: Organic Geochemistry, vol. 16, p. 369–387., 10., 1016/0146-6380(90)90055-5</ref> reprinted with permission from Elsevier.]]

Carbon isotope ratios are commonly measured on whole oils, kerogens, and whole extracts (bitumens) from rocks. In many cases they are also measured on the C₁₅₊ saturate and aromatic fractions and are often displayed on a Sofer.<ref name=ch08r50>Sofer, Z., 1984, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0068/0001/0000/0031.htm Stable carbon isotope compositions of crude oils: application to source depositional environments and petroleum alteration]: AAPG Bulletin, vol. 68, p. 31–49.</ref> diagram (e.g., the figure on the right, below). Less commonly, carbon isotope ratios are measured on the distillate and/or chromatographic fractions. For oil-[[source rock]] correlations, isotope ratios can also be measured on kerogen. Results of isotope analyses are often presented in a socalled Galimov diagram (left, below). Carbon isotope ratios can be characteristic of geologic age and environment.<ref name=ch08r4>Chung, H., M., Rooney, M., A., Toon, M., B., Claypool, G., E., 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0007/0000/1000.htm Carbon isotopic composition of marine crude oils]: AAPG Bulletin, vol. 76, p. 1000–1007.</ref><ref name=ch08r5>Chung, H., M., Rooney, M., A., Toon, M., B., Claypool, G., E., Rooney, M., A., Squires, R., M., 1994, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0078/0003/0350/0396.htm Source characteristics of marine oils as indicated by carbon isotopic ratios of volatile hydrocarbons]: AAPG Bulletin, vol. 78, p. 396–408.</ref>

Carbon isotope ratios are commonly measured on whole oils, [[kerogen]]s, and whole extracts (bitumens) from rocks. In many cases they are also measured on the C₁₅₊ saturate and aromatic fractions and are often displayed on a Sofer.<ref name=ch08r50>Sofer, Z., 1984, [http://archives.datapages.com/data/bulletns/1984-85/data/pg/0068/0001/0000/0031.htm Stable carbon isotope compositions of crude oils: application to source depositional environments and petroleum alteration]: AAPG Bulletin, vol. 68, p. 31–49.</ref> diagram (e.g., the figure on the right, below). Less commonly, carbon isotope ratios are measured on the distillate and/or chromatographic fractions. For oil-[[source rock]] correlations, isotope ratios can also be measured on kerogen. Results of isotope analyses are often presented in a socalled Galimov diagram (left, below). Carbon isotope ratios can be characteristic of geologic age and environment.<ref name=ch08r4>Chung, H. M., M. A. Rooney, M. B. Toon, and G. E. Claypool, 1992, [http://archives.datapages.com/data/bulletns/1992-93/data/pg/0076/0007/0000/1000.htm Carbon isotopic composition of marine crude oils]: AAPG Bulletin, vol. 76, p. 1000–1007.</ref><ref name=ch08r5>Chung, H. M., M. A. Rooney, M. B., Toon, G. E. Claypool, M. A. Rooney, and R. M. Squires, 1994, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0078/0003/0350/0396.htm Source characteristics of marine oils as indicated by carbon isotopic ratios of volatile hydrocarbons]: AAPG Bulletin, vol. 78, p. 396–408.</ref>

[[:file:oiloil-and-oilsource-rock-correlations_fig8-3.png|Figure 1]] shows carbon isotope ratios for fractions of six oils comprising two families from the Zagros orogenic belt. The “Galimov” plot (left) and the Sofer diagram (right) show the δ¹³C values. Oils 3 and 4 are from the Ahwaz field, whereas oils 13, 14, and 16 are from the northeastern Dezful area. The midrange position of oil 18 suggests that it could be a mixture of these two main oil types. These conclusions are also supported by molecular and elemental data.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-3.png|Figure 1]] shows carbon isotope ratios for fractions of six oils comprising two families from the Zagros orogenic belt. The “Galimov” plot (left) and the Sofer diagram (right) show the δ¹³C values. Oils 3 and 4 are from the Ahwaz field, whereas oils 13, 14, and 16 are from the northeastern Dezful area. The midrange position of oil 18 suggests that it could be a mixture of these two main oil types. These conclusions are also supported by molecular and elemental data.

Over the last decade, much interest has developed in compound-specific isotope analysis, in which carbon isotope ratios are measured for numerous individual compounds in a sample and then plotted to give a fingerprint.

Over the last decade, much interest has developed in compound-specific isotope analysis, in which carbon isotope ratios are measured for numerous individual compounds in a sample and then plotted to give a fingerprint.

In addition to ''n''-alkanes, isotope ratios have been measured for pristane, phytane, and other biomarkers.<ref name=ch08r1>Bjorøy, M., Hall, K., Gillyon, P., Jumeau, J., 1991, Carbon isotope variations in n-alkanes and isoprenoids of whole oils: Chemical Geology, vol. 93, p. 13–20., 10., 1016/0009-2541(91)90061-U</ref><ref name=ch08r6>Clayton, C., J., Bjorøy, M., 1994, Effect of maturity on 13C/12C ratios of individual compounds in North Sea oils: Organic Geochemistry, vol. 21, p. 737–750., 10., 1016/0146-6380(94)90016-7</ref> Although this technique is highly promising for correlations, initial attempts to interpret the data suggest that additional research to identify causes for isotopic variations will be necessary before the technique can be applied routinely and with confidence.

In addition to ''n''-alkanes, isotope ratios have been measured for pristane, phytane, and other biomarkers.<ref name=ch08r1>Bjorøy, M., K. Hall, P. Gillyon, and J. Jumeau, 1991, Carbon isotope variations in n-alkanes and isoprenoids of whole oils: Chemical Geology, vol. 93, p. 13–20., 10., 1016/0009-2541(91)90061-U</ref><ref name=ch08r6>Clayton, C. J., and M. Bjorøy, 1994, Effect of maturity on 13C/12C ratios of individual compounds in North Sea oils: Organic Geochemistry, vol. 21, p. 737–750., 10., 1016/0146-6380(94)90016-7</ref> Although this technique is highly promising for correlations, initial attempts to interpret the data suggest that additional research to identify causes for isotopic variations will be necessary before the technique can be applied routinely and with confidence.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-4.png|Figure 2]] shows an example of a correlation between an oil and a condensate using δ¹³C values for individual C₁₀ – C₂₇ ''n''-alkanes. These two samples are from a single oil field on the U.S. Gulf Coast. The condensate does not contain measurable ''n''-alkanes beyond ''n-''C₁₈, rendering biomarker techniques of little value. The similarity in ''n''-alkane δ¹³C values for these two samples supports the conclusion that they are sourced from similar organic facies.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-4.png|Figure 2]] shows an example of a correlation between an oil and a condensate using δ¹³C values for individual C₁₀ – C₂₇ ''n''-alkanes. These two samples are from a single oil field on the U.S. Gulf Coast. The condensate does not contain measurable ''n''-alkanes beyond ''n-''C₁₈, rendering biomarker techniques of little value. The similarity in ''n''-alkane δ¹³C values for these two samples supports the conclusion that they are sourced from similar [[organic facies]].

==Sulfur and hydrogen isotopes==

==Sulfur and hydrogen isotopes==

Sulfur isotopes are frequently measured for high-sulfur oils and related kerogens. They are useful primarily in distinguishing among various types of anoxic environments.<ref name=ch08r36>Orr, W., L., 1986, Kerogen/asphaltene/sulfur relationships in sulfur-rich Monterey oils: Organic Geochemistry, vol. 10, p. 499–516., 10., 1016/0146-6380(86)90049-5</ref> Hydrogen isotopes are used occasionally, particularly for gases. Interpretation of hydrogen isotopes for oils is difficult.<ref name=ch08r48>Schoell, M., 1982, Application of isotopic analyses in oil and natural-gas research: Spectra, vol. 8, no. 2 & 3, p. 32–41.</ref>

Sulfur isotopes are frequently measured for high-sulfur oils and related kerogens. They are useful primarily in distinguishing among various types of anoxic environments.<ref name=ch08r36>Orr, W. L., 1986, Kerogen/asphaltene/sulfur relationships in sulfur-rich Monterey oils: Organic Geochemistry, vol. 10, p. 499–516., 10., 1016/0146-6380(86)90049-5</ref> Hydrogen isotopes are used occasionally, particularly for gases. Interpretation of hydrogen isotopes for oils is difficult.<ref name=ch08r48>Schoell, M., 1982, Application of isotopic analyses in oil and natural-gas research: Spectra, vol. 8, no. 2 & 3, p. 32–41.</ref>

==References==

==References==

[[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]]