AAPG ANNUAL CONFERENCE AND EXHIBITION
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April 10-13, 2011, Houston, Texas, USA
USGS Assessment of Undiscovered Natural Gas Resources of the Ouachita Thrust Belt, Arkansas and Oklahoma, USA
(1) Department of Interior, U. S. Geological Survey, Reston, VA.
(2) Department of Interior, U. S. Geological Survey, Denver, CO.
The U. S. Geological Survey (USGS) has assessed mean volumes of 753 BCFG and 8 MMBNGL of undiscovered, technically recoverable gas resources in the Ouachita Thrust Belt of Arkansas and Oklahoma. Oil accumulations larger than 0.5 MMBO are not expected to be found. These resources were all attributed to the Arkoma - Ouachita Paleozoic Composite Total Petroleum System (TPS) and were determined to be most likely reservoired in conventional gas accumulations. The Ouachita Thrust Belt Assessment Unit (AU) encompasses that volume of Paleozoic rock extending from south of the structural front composed of the Ti Valley - Choctaw - Ross Creek - Bayou Meto fault zone; east of the Clear Boggy, Bryan, and Kingston faults, which define the boundary between the Tishomingo Uplift and the Ouachita Thrust Belt; north of the Red River boundary between Oklahoma and Texas and north of the main Gulf Coast Basin Mesozoic expansion fault zones; and west of the Black Warrior Basin Province in Mississippi. This area contains primarily thrust-faulted and folded Paleozoic strata, forming complex anticlinoria and anticline-syncline pairs, similar to that exposed in the Ouachita Mountains of Arkansas and Oklahoma. The Ouachita Thrust Belt AU extends over 430 miles from southeast Oklahoma to west central Mississippi and occupies approximately 25 million acres. Currently, only about 1/25th of this area is productive of oil and natural gas.
The Ouachita Thrust Belt AU contains at least 12 source rock intervals from Cambrian to Pennsylvanian in age. The most significant of this suite are the Ordovician Womble Shale and the Devonian Woodford Shale - Arkansas Novaculite. Two main reservoir intervals host much of the current and historic AU production: the Pennsylvanian Jackfork Sandstone and the Devonian Arkansas Novaculite, with additional contributions from the Pennsylvanian Atoka sandstone, the Mississippian Stanley sandstone, and the Ordovician Big Fork Chert. While the estimated undiscovered resources are characterized as conventional, there is some indication that a significant proportion of this gas may, in fact, be continuous, because several discovered gas accumulations are present outside of apparent structural closure in an area that is adjacent to the Arkoma - Ouachita Foredeep Continuous AU.