--> Abstract: Petroleum Geochemistry of Texas and Oklahoma Oils from the Marathon/Ouachita Fold Belt, by J. A. Curiale; #91004 (1991)

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Petroleum Geochemistry of Texas and Oklahoma Oils from the Marathon/Ouachita Fold Belt

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

The Marathon uplift of west Texas and the Ouachita Mountains of Oklahoma and Arkansas comprise the surface expressions of a Paleozoic orogenic belt extending across the south-central United States. A century of petroleum exploration in the Marathon and Ouachita exposures has yielded several oil discoveries. In this study, detailed molecular, elemental, and isotopic data are presented for nine Texas oils, five Oklahoma oils, and four Oklahoma solid bitumens, all associated with thrust belt rocks of the Marathons and Ouachitas. Oil-oil and oil-solid bitumen correlations are proposed, and the character of the organic matter in the source rock(s) is deduced from the chemistry of the oils and solid bitumens.

All 18 samples are sourced from the same (or very similar) organic matter. This indicates that they are probably cogenetic, despite geographic separations of hundreds of miles. Chemical differences in these samples derive from secondary effects, including biodegradation (e.g., solid bitumens) and differing levels of thermal maturity. The occurrence of unusual chemical compounds (certain bisnor- and trisnor-hopanes) in all samples probably indicates the presence of anaerobic bacteria in the depositional environment. Source deductions from oil chemistry suggest that an Ordovician unit is responsible for these oils and solid bitumens. This conclusion is consistent with previous literature suggesting an Upper Ordovician source for Oklahoma Ouachita oils and supports tectonic reconstructio s of the region during Ordovician time.

 

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