Reservoir-scale Facies and Stratigraphic Architecture of the Middle and upper Williams Fork Formation, upper Philadelphia Creek, Douglas Creek Arch, Colorado

John McFadden Jr., Rex D. Cole, and Matthew J. Pranter
University of Colorado at Boulder

This study explores the fluvial style and stratigraphic variability of the middle and upper Williams Fork Formation at the reservoir scale using high quality outcrops in upper Philadelphia Creek, Douglas Creek Arch, Colorado. The Late Cretaceous, upper interval (Kmvu) of the Mesaverde Group of the Douglas Creek Arch, is represented by a complex succession of crevasse splays and single-story, multistory, and amalgamated channel bodies that serve as outcrop analogs to laterally equivalent natural gas reservoirs in the Piceance and Uinta basins. Net-to-gross (N:G) ratios (generally >40% sandstone) present of this interval show direct ties to the stratigraphic framework and provide a predictive tool for subsurface reservoir characterization. Outcrop measured sections (N=6; 1,505 ft [458.7 m]) from Upper Philadelphia Creek were used to determine the characteristics and spatial relationships of lithofacies and architectural elements present in the study interval. Sections were spaced approximately 660 ft (201.2 m) apart to mimic the 10-acre well spacing commonly used by producers in the Piceance Basin. Spectral-gamma-ray (SGR) data were collected along measured section paths every foot in order to determine architectural element and lithofacies SGR signatures. Field descriptions, global-positioning-system (GPS) traverses, laser-ranging (LiDAR) data, and ground-based photomosaics were used to map and document the abundance, stratigraphic position, and dimensions of single-story and multistory channel bodies and crevasse splays. These data, in conjunction with recorded paleocurrent values and measured sections, are used to characterize the complex relationship between low-sinuosity braided and high-sinuosity meandering river deposits present in the middle and upper Williams Fork Formations.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013