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AAPG Bulletin
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AAPG Bulletin; Year: 2020; Issue: June DOI: 10.1306/0122201618217407
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Figure 11. Plot of C27 βα 20(S + R)/[C27 βα 20(S + R) + C29 ααα 20(S + R) + C29 αββ 20(S + R) (diasterane/sterane ratios) against (diginane + 5α pregnane + 20-methyldiginane + 5α methylpregnane)/[(diginane + 5α pregnane + 20-methyldiginane + 5α methylpregnane) + (C29 ααα 20(S+R) + C29 αββ 20(S+R))] (pregnane ratios), showing that most of the Niger Delta oil samples appear of lower maturity than the those of the thermally mature North Sea oil. Five Niger Delta oil samples biodegraded up to level 6, as described in Peters and Moldowan (1991), were excluded from the plot.
Figure 11. Plot of C27 βα 20(S + R)/[C27 βα 20(S + R) + C29 ααα 20(S + R) + C29 αββ 20(S + R) (diasterane/sterane ratios) against (diginane + 5α pregnane + 20-methyldiginane + 5α methylpregnane)/[(diginane + 5α pregnane + 20-methyldiginane + 5α methylpregnane) + (C29 ααα 20(S+R) + C29 αββ 20(S+R))] (pregnane ratios), showing that most of the Niger Delta oil samples appear of lower maturity than the those of the thermally mature North Sea oil. Five Niger Delta oil samples biodegraded up to level 6, as described in Peters and Moldowan (1991), were excluded from the plot.