Oil-Source Rock Correlation--A Powerful Geochemical Tool for the Petroleum Explorationist

CURIALE, JOSEPH A., Unocal, Inc., Brea, CA

A successful oil-source rock correlation results from the application of geological and geochemical methods to establish a genetic relationship between a petroleum source rock and crude oil. Molecular (hydrocarbon biomarker and heterocompound concentrations and ratios), isotopic (stable carbon and sulfur isotope ratios), and elemental (concentration of sulfur, vanadium, nitrogen, etc.) geochemical comparisons are necessary parameters of an oil-source rock correlation, but they are not sufficient. Geological knowledge of basinal history and structural setting must also be applied to deduce migration timing and pathway(s). Geologically "blind" correlations often lead to misinterpretations.

As a part of an oil-source rock correlation, the geochemist must distinguish between the genetic (source-induced) and nongenetic (maturation-, migration-, and alteration-induced) processes affecting the chemistry of crude oil. Techniques for making such a distinction are described here. In addition, worldwide examples of successful oil-source rock correlations are reviewed from geological and geochemical perspectives. Finally, anticipated technological advances are discussed, including (1) whole oil/whole source rock correlation efforts using pyrolysis-gas chromatography coupled to high resolution mass spectrometry and (2) compound-specific stable carbon isotope ratio techniques (i.e., GC-IRMS). Using these techniques and others we will eventually be able to analyze the entire oil and thus, fully acquire complete information about its source rock characteristics and post sourcing history.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)