Geology and Assessment of Undiscovered Oil and Gas Resources in Tertiary Strata of the Gulf Coast, U.S.A

Russell F. Dubiel¹ and Peter D. Warwick^2
1U.S. Geological Survey, Denver, CO
²U.S. Geological Survey, Reston, VA

The U.S. Geological Survey (USGS) completed an assessment of undiscovered oil and gas resources in Tertiary strata of the onshore coastal plain and State waters of the Gulf Coast of the United States. The assessment is based on geologic elements of a total petroleum system (TPS), including hydrocarbon source rocks (source-rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and hydrocarbon traps (trap formation, timing, and seals). Using these criteria, the USGS defined an Upper Jurassic-Cretaceous-Tertiary Composite TPS for conventional oil and gas resources that extends around the entire Gulf of Mexico, including portions of both the United States and Mexico. However, the present assessment of undiscovered conventional oil and gas resources includes only that portion of the TPS that lies onshore and in State waters of the United States. The Upper Jurassic-Cretaceous-Tertiary Composite TPS contains 33 assessment units (AUs) for undiscovered conventional oil and gas resources that lie on the coastal plain and in State waters. Undiscovered conventional oil and gas resources are interpreted to reside primarily in clastic reservoirs that were deposited on continental shelves, in shelf-margin deltas, and in slope fans and basin-floor fans that formed lowstand systems tracts in response to episodic fluctuations in sea level. Additionally, four AUs were defined for continuous coalbed gas in both Cretaceous and Tertiary strata. The USGS assessment of undiscovered conventional oil and gas resources and continuous coalbed gas resources from the defined AUs resulted in estimated means of 113.7 trillion cubic feet of gas, 690 million barrels of oil, and 3.7 billion barrels of natural gas liquids.

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