Unconventional petroleum potential in the Mowry Shale, Southern Powder River Basin, Wyoming

Abstract

The Lower Cretaceous Mowry Shale is a major source rock in the northern Rocky Mountain region (Schrayer and Zarrella, 1968; Nixon, 1973; Byers and Larson, 1979; Burtner and Warner, 1984; Momper and Williams, 1984; Davis et al., 1989; Modica and Lapierre, 2012). The source rock contains primarily Type II organic matter with an admixture of Type III kerogen towards the west. Thermally mature Mowry Shales are closely associated with petroleum accumulations in both Lower and Upper Cretaceous reservoirs. The Mowry Shale has produced modest amounts of oil from older vertical wells in the Powder River basin (Figure 1). With technology improvements (horizontal drilling and multistage hydraulic fracture stimulation) over the past decade, the Mowry is now a prospective target for hydrocarbon production (Finley, 2017). Horizontal drilling is currently targeting the Mowry in the deeper parts of the Powder River Basin. The Mowry Shale overlies the Shell Creek Shale or Muddy/Newcastle sandstones and is overlain by the Frontier Formation or Belle Fourche Shale (Figure 2). The Mowry petroleum system consists of the Mowry source rock and the following Cretaceous reservoirs: Lakota, Fall River, Muddy, Newcastle, Mowry, Frontier, and Turner.