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Line 28: + + + − The figures below are typical gas chromatograms of saturated hydrocarbons for group I (left) and group IV (right) oils from the Brazilian continental margin. Note the many source-distinctive differences, including pristane–phytane ratio and the dominance of waxy ''n''-alkanes in the group I oil. Supplemental numerical data indicate these differences extend to the sulfur concentration, the vanadium–nickel ratio, and the δ<sup>13</sup>C value.+ − − [[file:oiloil-and-oilsource-rock-correlations_fig8-49.png|thumb|{{figure number|8-49}}From Mello et al.<ref name=ch08r30 />); reprinted with permission from Marine and Petroleum Geology.]]
Oil correlation case history: Brazilian offshore basins (view source)
Revision as of 21:13, 13 February 2014
, 21:13, 13 February 2014→Group I oils, freshwater lacustrine setting
==Group I oils, freshwater lacustrine setting==
==Group I oils, freshwater lacustrine setting==
[[file:oiloil-and-oilsource-rock-correlations_fig8-49.png|thumb|{{figure number|2}}From Mello et al.<ref name=ch08r30 />); reprinted with permission from Marine and Petroleum Geology.]]
For illustrative purposes, we discuss here differences in the characteristics of group I and group IV oils.<ref name=ch08r30 /> The group I oils are very low in sulfur (13C values more negative than –28.0 ‰. Concentrations of diasteranes, steranes, 4-methylsteranes, and gammacerane are low; ''n''-propylcholestanes (C<sub>30</sub> steranes) are absent. A distinctive odd-carbon ''n''-alkane dominance and a waxy appearance to the [[gas chromatogram]] of these oils is evident. These and other features suggest a freshwater lacustrine depositional setting.
For illustrative purposes, we discuss here differences in the characteristics of group I and group IV oils.<ref name=ch08r30 /> The group I oils are very low in sulfur (13C values more negative than –28.0 ‰. Concentrations of diasteranes, steranes, 4-methylsteranes, and gammacerane are low; ''n''-propylcholestanes (C<sub>30</sub> steranes) are absent. A distinctive odd-carbon ''n''-alkane dominance and a waxy appearance to the [[gas chromatogram]] of these oils is evident. These and other features suggest a freshwater lacustrine depositional setting.
[[:file:oiloil-and-oilsource-rock-correlations_fig8-49.png|Figure 2]] represents typical gas chromatograms of saturated hydrocarbons for group I (left) and group IV (right) oils from the Brazilian continental margin. Note the many source-distinctive differences, including pristane–phytane ratio and the dominance of waxy ''n''-alkanes in the group I oil. Supplemental numerical data indicate these differences extend to the sulfur concentration, the vanadium–nickel ratio, and the δ<sup>13</sup>C value.
==Group I and group IV oils contrasted==
==Group I and group IV oils contrasted==