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AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Great Basin oil shales


The Great Basin contains age equivalent North American oil shales including the Ordovician Utica, Middle Devonian Marcellus, Mississippian-Devonian Bakken, Mississippian Barnett, Permian Bone Springs, and Eocene Uinta Basin oil shales. However, Great Basin age equivalent shales are typically much thicker, spatially more expansive, and are as organically rich as the other America shales. Ordovician Vinini shales found in hanging wall of the Roberts Mountain thrust fault are thousands of feet thick, produce good oil and gas shows in some wells, and are organically-rich enough to retort oil. Middle Devonian Simonson oil shales, exposed in a thrust fault fenster are hundreds of feet thick and boast of oil seeps. It has yet to be penetrated by a well. Mississippian-Devonian Pilot oil shale gets up to 900 feet thick in places, produces oil and gas shows in wells, is high in vanadium like the Bakken, and boasts of at least two surface oil occurrences. It is probably the source of the five million barrel Blackburn oil field. Mississippian Antler basin oil shales, sometimes called Chainman shale, make up about five thousand feet of Antler clastics is several measured sections, almost always produce good oil and gas shows in wells, are related to several seeps and surface oil occurrences, and are believed to be the source for the fifty million barrels of oil produced in Railroad Valley and the seven hundred million barrel Covenant field in central Utah. Furthermore, it is likely the source for the giant tar sands in eastern Utah and the hydrocarbons trapped at the leading edge of the Cordillera thrust belt in southwest Wyoming and northern Utah. Great Basin Permian oil shales have not been drilled and/or studied adequately. They are hundreds of feet thick in some sections and nearly always produce a strong hydrocarbon odor when freshly broken.