Sedimentation and subsurface characterization of the Lower Cretaceous muddy sandstone and the Upper Cretaceous Shell Creek and Mowry shales, Powder River Basin, Wyoming

Chavez, Chase Emilio

Item

Sedimentation and subsurface characterization of the Lower Cretaceous muddy sandstone and the Upper Cretaceous Shell Creek and Mowry shales, Powder River Basin, Wyoming

Chavez, Chase Emilio

Date

2025-04-28

Abstract

Foreland basins comprise some of the most prolific hydrocarbon producing reservoirs and source rocks in the North American Rocky Mountain region. One of these major producing basins is the Powder River Basin (PRB). Located in northeastern Wyoming and extending into southeastern Montana, the PRB is one of Wyoming’s largest and most active hydrocarbon producing basins. The basin comprises various Mesozoic and Paleozoic strata with productive conventional and unconventional plays. This study focuses on the upper Lower Cretaceous Muddy Sandstone Formation and lower Upper Cretaceous Mowry Shale intervals at basin scale, and the implications for tectonic and eustatic evolution prior to the development of the PRB. Which controlled sedimentation, infilling, and Total Organic Carbon (TOC) weight percentage distributions of the two formations. The Muddy being an older conventional reservoir and the Mowry a more recent unconventional play, the collection and utilization of digitized well log data from Enverus Prism with Petrel Software, in conjunction with analysis of in-house core, provides an effective approach for producing refined structure, isochore, net sand, and TOC maps for the basin. This information can then be used in generating interpretations of sedimentation history, basin infilling, and TOC distribution. In addition, published type wells with correlated Paleozoic stratigraphy from the United States Geological Survey (USGS) are being used to generate PRB subsidence curves for multiple well locations throughout the basin to compare with maps and figures produced in Petrel. To further enhance sedimentation interpretations, U-Pb detrital zircon analysis is conducted on the Muddy Formation sandstones collected from core. These data are compared with published detrital zircon work done in the western neighboring Big Horn Basin and its equivalent Muddy Formation interval, as well as equivalent Muddy Formation from the Black Hills to the east within North Dakota.