Assessment of Undiscovered, Technically Recoverable, Oil and Natural Gas Resources of the Eocene Jackson and Oligocene Vicksburg Groups, Onshore Gulf of Mexico Basin, U.S.A

James L. Coleman and Daniel O. Hayba
Department of Interior, U. S. Geological Survey, Reston, VA

The USGS has recently completed a resource assessment of the Upper Eocene Jackson and Lower Oligocene Vicksburg Assessement Units (AUs) of the Upper Jurassic - Cretaceous - Tertiary Composite Total Petroleum System in the Gulf of Mexico Basin. Stable shelf oil and gas, expanded fault zone gas and oil, and slope and basin floor gas AUs were defined based on source rock, migration pathway, structure, and sedimentology. Mean undiscovered resources of 61 MMBO, 987 BCFG, and 1 MMBNGL were attributed to the Jackson AUs, and 172 MMBO, 17896 BCFG, and 5 MMBNGL were attributed to the Vicksburg AUs.

Hydrocarbons have been produced for over 80 years from sandstone reservoirs in the Jackson and Vicksburg Groups in the Gulf Coastal Plain of Texas and Louisiana. Jackson Group reservoirs are primarily shallow water marine sandstones in stratigraphic traps in the Lower Texas Coast, and fluvial deltaic sandstones in structural traps in the Upper Texas Coast. Vicksburg Group fluvial-deltaic sandstone reservoirs extend from the Rio Grande to southwestern Louisiana in combination traps on large fault blocks in the Lower Texas Coast and on salt domes and faulted anticlines in the Upper Texas Coast and southwestern Louisiana. Remaining discoveries in both of these trends will probably be extensions of existing fields.

Future potential resources will probably be located where down-to-the-basin faults have translated these groups below previous economic drilling depths or beneath established Upper Oligocene Frio Formation sandstone production. New discoveries in the Burgos and Houston Salt Dome Basins suggest that additional fields will be found with deeper drilling.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas