Similarities and Contrasts Among Major Paleozoic Shale Gas Reservoir Plays in Texas and New Mexico

Ruppel, Stephen C.¹, R. G. Loucks², Wayne R. Wright³, Jeffrey A. Kane⁴, Fred P. Wang⁵ (1) University of Texas at Austin, Austin, TX (2) Bureau of Economic Geology, Jackson School of Geosciences,The University of Texas at Austin, Austin, TX (3) The University of Texas, Austin, TX (4) Jackson School of Geosciences, The University of Texas at Austin, Austin, TX (5) The University of Texas at Austin, Austin, TX

Dramatic success in exploitation of the Mississippian Barnett Shale in the Ft. Worth Basin (FWB) of central Texas has ignited interest in shale successions around the globe. In Texas, four middle and upper Paleozoic shale successions are known to be oil source rocks and have the potential to produce significant shale gas. Each succession, however, exhibits distinctive differences from the FWB Barnett and from one another that need to be recognized and interpreted before their gas production potential can be assessed. For example, both the Devonian Woodford shale (up to 700 ft thick) and Barnett of the Permian Basin of Texas and New Mexico (up to 1600 ft thick) were deposited under very similar conditions to the FWB Barnett, contain similar high TOC, kerogen, and thermal maturity, and are distributed over much larger areas than the FWB Barnett but both are at greater depths and appear to be very different mineralogically. Permian Basin Pennsylvanian and Permian shale successions are similarly widespread and much thicker (up to 5,000 and 12,000 ft, respectively) but are even less well characterized. Pennsylvanian Smithwick/Atoka shales overlying the Barnett in the FWB also display high TOC, kerogen quality, and thermal maturity and are much thicker than the Barnett, but are also poorly known. New studies of these four source rock shale successions provide important new insights into their sedimentology, mineralogy, geochemistry, fracture character, and potential as economic shale gas reservoirs.