MORELOS-GARCIA, J. A., and R. M. MITTERER, University of Texas at Dallas, Richardson, TX; and R. SASSEN, P. COMET, and J. BROOKS, Geochemical and Environmental Research Group, College Station, TX

ABSTRACT: Organic Geochemistry of Southern Tampico-Misantla Basin, Mexico: Oil-Oil and Oil-Source Rock Correlation

Most oil in the southern Tampico-Misantla Basin is in middle Cretaceous reservoirs of the Golden Lane and Poza Rica Trend, with additional production from Upper Jurassic and Eocene reservoirs. Geochemical characterization of oils and potential source rocks from Tertiary, Cretaceous, and Upper Jurassic formations of this area is based on stable carbon isotopes, n-alkane and biomarker distributions of oils and rock extracts.

The data suggests that the oils have a common origin, and that they were generated from an organic carbon-rich carbonate source rock deposited in an anoxic environment. Tertiary formations are thermally immature and are regarded as poor source rocks, while Cretaceous formations have entered the oil window and are considered to be fair source rocks. Upper Jurassic formations (i.e., Santiago, Taman, and Pimienta Formations) are good source rocks in the early stage of oil generation. Upper Jurassic Formations in the study area consist of shales and carbonates, and were deposited in environments from suboxic to anoxic.

Despite certain similarities, it is difficult to correlate oils and source rocks in the study area. Therefore, it is possible that this Upper Jurassic-Cretaceous section has not contributed significantly to the oils entrapped locally. These data, and geologic interpretation, imply that oils have migrated from a deeper facies downdip of the study area, most likely from offshore Gulf of Mexico.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.