--> Abstract: USGS Assessment of Undiscovered Oil and Gas Resources in the Oligocene Frio and Anahuac Formations, Onshore Gulf of Mexico Basin, U.S.A, by Sharon M. Swanson and Alexander W. Karlsen; #90078 (2008)

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USGS Assessment of Undiscovered Oil and Gas Resources in the Oligocene Frio and Anahuac Formations, Onshore Gulf of Mexico Basin, U.S.A

Sharon M. Swanson and Alexander W. Karlsen
U.S. Geological Survey, Reston, VA

The sand-rich, fluvio-deltaic Oligocene Frio Formation, a mature to supermature exploration trend, has been one of the largest hydrocarbon producers from Paleogene strata in the Gulf of Mexico Basin. The overlying Anahuac Formation is a transgressive marine shale having deltaic, shoreface, and slope sandstones in addition to carbonate sediments. In a recent U.S. Geological Survey assessment of undiscovered, technically recoverable oil and gas resources in Tertiary strata of onshore lands and State waters, estimated total mean values of undiscovered resources for the Frio and Anahuac Formations were 172 million barrels of oil, 9,384 billion cubic feet of natural gas (BCFG), and 542 million barrels of natural gas liquids. Five assessment units (AUs) for the Frio (including the Hackberry embayment) and Anahuac Formations were quantitatively assessed. Three of the Frio AUs were defined based on the character of reservoirs in relation to structural and depositional features: (1) the “Frio Stable Shelf Oil and Gas AU”, containing reservoirs with a mean depth of about 4,800 ft in normally pressured intervals; (2) the “Frio Expanded Fault Zone Oil and Gas AU”, containing reservoirs with a mean depth of about 9,000 ft in overpressured intervals; and (3) the “Frio Slope and Basin Floor Gas AU”, which currently has no production, but has potential for deep gas resources (>15,000 ft). AUs also were defined for the Hackberry embayment and the Anahuac Formation. Of the five units assessed, the “Frio Slope and Basin Floor Gas AU” shows the greatest potential for undiscovered gas resources, having an estimated mean of 5,589 BCFG.

 

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