Abstract: Hydrocarbon Systems of the Northern Gulf of Mexico Basin - Delineation through Integration of Geochemical and Geophysical Approaches
Lloyd M. Wenger, Kenneth C. Hood, Stanley C. Harrison, Oliver P. Gross, Alan T. James
The sources for hydrocarbons in young Tertiary reservoirs of the offshore Gulf of Mexico have been enigmatic in the past due to the lack of source rock penetration. To better understand the hydrocarbon systems, Exxon has carried out an integrated, multidisciplinary study of hydrocarbon sources, maturation, and migration pathways in the offshore U.S. Gulf of Mexico. We developed a geologic framework from 2-D and 3-D seismic specifically acquired to image the complete hydrocarbon system. Hydrocarbon compositions from over 2000 oils, 600 gases, and 1200 hydrocarbon-bearing sea bottom dropcores, provide insights into regional characteristics and maturity of source rocks. Direct hydrocarbon to source rock correlations were made onshore, offshore east of the present day Mississippi. River Delta, and from sheaths overlying salt diapirs in the western Gulf of Mexico. The major sources identified offshore are centered on the Eocene, Turonian, Tithonian, and Oxfordian.
Cross-stratal migration is required to move hydrocarbons from deep source intervals to young Tertiary reservoirs. Cross-stratal conduits are formed by two mechanisms: salt-movement and faulting, and are most effective where disruption between source and reservoir is greatest. Modern seismic, e.g., 6000 m cable and 15 sec. recording times, provide dramatic improvements in imaging migration pathways and deep source intervals. Improved understanding of regional hydrocarbon systems has provided new exploration methodologies and play concepts.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela