Comparison of Producing and Potential Shale Gas Reservoirs in the Eastern United States
Gas shale reservoirs are the latest continuous hydrocarbon resource to be brought into the mainstream of US petroleum production as significant production fairways in shale basins are being developed across the United States. Even though shale gas was being produced from Devonian strata as early as 1821 in the Appalachian Basin of the eastern United States, it was not until natural gas prices and technology advanced that additional shale gas resources could be developed more widely. Now, as many as thirty shale intervals of Precambrian to Cretaceous age may continue as or potentially become viable shale gas reservoirs east of the Mississippi River.
At least fourteen different Paleozoic shale gas intervals are currently being produced or undergoing testing in the Appalachian, Michigan, and Illinois Basins. Sixteen other candidate shale gas reservoir intervals are in the Precambrian Nonesuch Formation and generally equivalent shales of Precambrian rift basins, a Silurian shale with a Gondwanan affinity in North Florida - South Georgia, the Triassic Lockatong Formation and generally equivalent shales in Mesozoic rift basins, and shales in the Jurassic Bossier and lower Smackover and Cretaceous Eagle Ford Formations of the Gulf Coast Basin. Natural gas within these shale reservoirs may be thermogenic and (or) biogenic, and different exploration concepts may be needed for these different gas types. Examination of each potential interval and comparison with existing producing intervals show key commonalities (such as thickness, depth, and total organic carbon content) and potential significant differences (such as thermal maturity, structural style, and organic matter characteristics and convertibility).
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas