Assessment of the Mowry Shale and Niobrara Formation as Continuous Hydrocarbon Systems, Powder River Basin, Montana and Wyoming

Map of assessed continuous (unconventional) oil resources in the United States, 2014

“…The Niobrara Formation averages more than 3 weight percent TOC of Type II kerogen (Anna and others, 2009). Burial-history modeling by Anna and Cook (2008) indicated that hydrocarbon generation for both the Mowry Shale and the Niobrara Formation started at about 0.60 percent R o at depths of about 8,000 feet. At maximum depths, R o for the Mowry is about 1.2 to 1.3 percent and about 0.80 percent for the Niobrara.…”

“…At maximum depths, R o for the Mowry is about 1.2 to 1.3 percent and about 0.80 percent for the Niobrara. Anna and Cook (2008) defined overpressuring caused by hydrocarbon generation at an upper depth limit of 8,000 ft. Current and historical production data from unconventional fractured shale reservoirs with vertical wells were used to determine the EUR distribution for untested cells. Anna and Cook (2008) contended that horizontal drilling, state-of-the-art completion practices, and comprehensive fracture and fault analysis might increase the Mowry and Niobrara EUR distribution analogous to the Permian Spraberry Formation EURs in the Permian Basin, Texas.…”

“…Anna and Cook (2008) defined overpressuring caused by hydrocarbon generation at an upper depth limit of 8,000 ft. Current and historical production data from unconventional fractured shale reservoirs with vertical wells were used to determine the EUR distribution for untested cells. Anna and Cook (2008) contended that horizontal drilling, state-of-the-art completion practices, and comprehensive fracture and fault analysis might increase the Mowry and Niobrara EUR distribution analogous to the Permian Spraberry Formation EURs in the Permian Basin, Texas. Mean estimates of undiscovered, technically recoverable, continuous-oil resources in the Powder River Basin are 0.42 BBO, 424 BCFG, and 25 MMBNGL (Anna and others, 2006).…”

“…The AU occupies approximately 1,000 mi 2 in the eastern and southern parts of the Bighorn Basin, and extends to depths of 12,000 ft (Finn and others, 2010). The closest analog for the Mowry Fractured Shale Continuous-Oil AU is the Mowry Continuous-Oil AU in the Powder River Basin (Anna and Cook, 2008); however, the Mowry source rock there has higher TOC content and Type II kerogen (Burtner and Warner, 1984). The mean estimate for undiscovered, technically recoverable oil resources in the Mowry Fractured Shale Continuous-Oil AU has potential for additions to reserves of 0.005 BBO and 2 BCFG (Kirschbaum and others, 2008).…”

Natural fracture systems in Mowry Shale outcrops, Bighorn Basin, Wyoming

“…The Upper Cretaceous Mowry Shale has long been recognized as a source rock for unconventional hydrocarbon production within the Laramide structural basins of Wyoming (Schrayer and Zarrella, 1963;Davis, 1970;Davis et al, 1989;Anna and Cook, 2008;Finn, 2010). In addition, recent studies by the Wyoming and U.S. Geological…”