Origin of Crude Oil in the Wilcox Trend of Louisiana and Mississippi: Evidence of Long-Range Migration

Roger Sassen, Robert S. Tye, Elizabeth W. Chinn, Rowdy C. Lemoine

Geochemical characterization of crude oils from Wilcox reservoirs in central Louisiana and southwestern Mississippi suggests they represent a single crude oil family that is distinct when compared with crude oils in deeper Tuscaloosa and Smackover reservoirs. This observation is consistent with geologic constraints that suggest an origin of crude oil from within the Wilcox Group itself. Although shales of the shallow Wilcox Group in central Louisiana and southwestern Mississippi contain gas-prone kerogen and are thermally immature, a more oil-prone source facies is present in marine shales of the deep Wilcox Group in south-central Louisiana. Thermal maturity measurements based on pyrolysis suggest a broad area of effective Wilcox source rock in south-central Louisiana. Mi ration distances from source to reservoir rocks of the downdip Wilcox Trend of south-central Louisiana appear to be relatively short. However, long-range updip migration (sometimes > 100 km) from deeply buried Wilcox source facies provides the best explanation for emplacement of crude oil in the shallow Wilcox Trend of central Louisiana and southwestern Mississippi.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.