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Assessing Undiscovered, Technically Recoverable Oil and Gas Resources of the Mississippian Barnett Shale


The Mississippian Barnett Shale within the Dallas-Fort Worth Basin, Texas is one of the most developed and productive self-sourced shale-gas reservoirs in the U.S. The Barnett Shale is also well established as a premier analog for comparing additional prospective shale-gas plays on a global scale with regard to reservoir characteristics and exploration and production techniques. The most recent U.S. Geological Survey (USGS) assessment for the Barnett Shale was released in 2004, which established an estimated mean of 26.7 trillion cubic feet (TCF) of undiscovered natural gas, a mean of 98.5 million barrels of undiscovered oil, and a mean of 1.1 billion barrels of undiscovered natural gas liquids within reservoirs of the Bend Arch-Fort Worth Basin Province. These assessment numbers reflect postulated undiscovered, technically recoverable resources only. Although the 2004 assessment included additional conventional Paleozoic clastic and carbonate reservoirs, over 98% of the projected undiscovered natural gas resource was attributed to continuous gas within the Barnett Shale. Most recently, the Bureau of Economic Geology (BEG) in Austin, Texas completed a comprehensive assessment of the Barnett Shale (2013) and estimated approximately 44 trillion cubic feet of recoverable resources based on production histories and decline-curve analyses culled from over 16,000 wells drilled within the basin through 2011. Although the BEG predicts the Barnett Shale will remain a major contributor to shale-gas production through 2030, their assessment methodology incorporates several economic parameters that are not utilized within the established USGS based methodology for oil and gas assessments. In order to revise estimates made in 2004, the USGS is currently reassessing the Barnett Shale to provide a non-economic based assessment of remaining undiscovered, technically recoverable oil and gas resources. This new resource assessment of the Barnett Shale will included a more detailed understanding of the unit's Geology and resource potential based on improved geologic mapping related to lithology, geochemistry, and thermal maturity trends. Ongoing geochemical analyses includes: (1) determining regional total organic carbon (TOC) trends, (2) establishing thermal maturation windows and oil and gas generation zones via vitrinite reflectance measurements and Rock-Eval data, and (3) defining reservoir properties of the Barnett Shale petroleum system.