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Application of Isotopic Type Curves to Multiple Source Oil-Source Rock Correlation in the Gulf of Suez, Egypt

M. Y. Zein El Din, Essam M. Shaltout

Isotopic type curves are obtained by plotting carbon isotopic ratios of the saturate, aromatic, NOSs, and asphaltene fractions according to increasing polarity. Extrapolating the regression line, a good approximation of the measured ^dgr13C values of the genetically related kerogen can be obtained.

Isotopic type curves for 46 crude oil samples from 15 fields in the Gulf of Suez, Egypt, were constructed. In all the analyzed samples the ^dgr13C values of asphaltene fractions were found to deviate from the regression line towards the more negative ^dgr13C values. The data suggest that these oils were generated from multiple sources. The main part of saturate and aromatic fractions is derived from a relatively more mature source rock. By linear extrapolation of ^dgr13C values of saturate and aromatic fractions, the ^dgr13C value of kerogen of the mature source rock can be calculated. The main part of the asphaltene fraction might have been derived from a relatively less-mature source rock, and its ^dgr13C value was used to calcu ate ^dgr13C value of the genetically related kerogen.

The oil in each field is thought to be sourced from two different source rocks. The more mature one has ^dgr13C values of kerogen that vary from one field to another, while the second, less-mature source has commonly provided oil to all studied fields.

This conclusion may prove to be very helpful in oil prospecting in the studied area.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.