Abstract: Tertiary Petroleum System in the Northern Gulf of Mexico: United States and Mexico

Richard C. Haack, Jeremy E. Dahl, Wendell G. Olivier, Genaro Ziga-Rodriguez, R. L. Kaufman

In the onshore portion of the northern Gulf of Mexico, Tertiary source rocks are the principle factor controlling the transition regionally from oil and wet gas reservoirs in south Louisiana to dry gas reservoirs in southeast Texas and northeast Mexico. Gas Yield, calculated from Energy Information Administration Annual Reports, for gas reservoirs in the Houston Embayment and south Louisiana averages 70 Bbls condensate/MMCFG (moderately wet), and progressively decreases to less than 10 Bbls condensate/MMCFG in the Burgos basin of northeastern Mexico (extremely dry). Concomitantly, the amount of oil production also decreases from Louisiana to Mexico.

To the northeast (south Louisiana), Sassen (1990) concluded that Midway, Wilcox and Sparta strata were sources of oil in Tertiary reservoirs and noted a decrease in oil proneness to the west. To the southwest (southeast Texas and northeast Mexico), sterane and hopane biomarkers from condensates indicate Tertiary source rocks are gas-prone, and TOC/Rock-Eval data consistently imply gas-prone characteristics. Additionally, biomarker-maturity parameters and results from thermal modeling indicate that gas-prone source rocks, younger than the Midway and Wilcox, must make a significant contribution to source potential. We conclude therefore, from biomarker and TOC/Rock-Eval data as well as regional trends in hydrocarbon production, that Tertiary source rocks south of the Houston Embayment a e predominantly dry gas-prone. In contrast, in the Houston and Mississippi Embayments, wet gas-prone and oil-prone source rocks are significant contributors to Tertiary source potential.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994