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Line 72: − − [[file:oiloil-and-oilsource-rock-correlations_fig8-13.png|left|thumb|{{figure number|9}}Gas chromatograms of two oils from Wyoming. From Peters and Moldowan;<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> reprinted with permission from Prentice-Hall.]] + + + + + Line 83:
Line 86: − − [[file:oiloil-and-oilsource-rock-correlations_fig8-14.png|thumb|{{figure number|10}}Gas chromatograms of saturated hydrocarbons from an immature extract of coaly organic matter (top) and an oil with a fairly high wax content believed to have been sourced from a similar facies (bottom). Copyright: Unocal.]]
Gas chromatography: data obtained (view source)
Revision as of 13:20, 21 May 2014
, 13:20, 21 May 2014→Limitations due to maturity differences
==Limitations due to maturity differences==
==Limitations due to maturity differences==
Maturity-related differences are often observed when comparing oils with each other and with source rock extracts. High-wax oils are affected most strongly by maturity. Maturity differences involving source rocks can present particular difficulties when source rock samples are extremely immature.
Maturity-related differences are often observed when comparing oils with each other and with source rock extracts. High-wax oils are affected most strongly by maturity. Maturity differences involving source rocks can present particular difficulties when source rock samples are extremely immature.
For these reasons, and also because of the possibility of fortuitous similarities between unrelated samples, gas chromatography seldom provides definitive positive correlations. It may, however, provide fairly definitive negative correlations. When used in conjunction with other correlation parameters, it can often be valuable for positive correlations as well, as demonstrated in the following two examples.
For these reasons, and also because of the possibility of fortuitous similarities between unrelated samples, gas chromatography seldom provides definitive positive correlations. It may, however, provide fairly definitive negative correlations. When used in conjunction with other correlation parameters, it can often be valuable for positive correlations as well, as demonstrated in the following two examples.
<gallery mode=packed heights=200px widths=200px>
file:oiloil-and-oilsource-rock-correlations_fig8-13.png|{{figure number|9}}Gas chromatograms of two oils from Wyoming. From Peters and Moldowan;<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> reprinted with permission from Prentice-Hall.
file:oiloil-and-oilsource-rock-correlations_fig8-14.png|{{figure number|10}}Gas chromatograms of saturated hydrocarbons from an immature extract of coaly organic matter (top) and an oil with a fairly high wax content believed to have been sourced from a similar facies (bottom). Copyright: Unocal.
</gallery>
===Maturity difference example===
===Maturity difference example===
===Examples of maturity differences===
===Examples of maturity differences===
[[:file:oiloil-and-oilsource-rock-correlations_fig8-14.png|Figure 10]] shows gas chromatograms of saturated hydrocarbons from an immature extract of coaly organic matter (top) and an oil with a fairly high wax content believed to have been sourced from a similar facies (bottom). Both show many of the same characteristics—high wax content, odd-carbon preference in the wax range, high pristane–phytane ratio—but maturity effects have changed many of the details.
[[:file:oiloil-and-oilsource-rock-correlations_fig8-14.png|Figure 10]] shows gas chromatograms of saturated hydrocarbons from an immature extract of coaly organic matter (top) and an oil with a fairly high wax content believed to have been sourced from a similar facies (bottom). Both show many of the same characteristics—high wax content, odd-carbon preference in the wax range, high pristane–phytane ratio—but maturity effects have changed many of the details.