Geologic Controls on Oil Production from the Niobrara Formation, Silo Field, Laramie County, Wyoming

Carrie M. Welker¹, Lisa Stright¹, and Thomas Anderson^2
1University of Utah, Salt Lake City, UT
²Energy & Geoscience Institute, Salt Lake City, UT

The Niobrara Formation, a carbonate-rich mudstone deposited during the Late Cretaceous in the Western Interior Seaway, is an important hydrocarbon play throughout the Rocky Mountain region. In the Denver basin, the basal Fort Hays Limestone Member is overlain by the Smoky Hill Member, a series of three chalk and marl cycles. Silo Field, located in the Denver Basin in Laramie County, Wyoming, has been producing almost exclusively from the Niobrara since 1981. Vertical wells were drilled in the 1980s, followed by horizontal wells in 1990. Horizontal drilling using modern technology began ~2005. Cumulative production to date is ~11.0 MMBO and 9,997 MMCF. At Silo Field, the Niobrara is ~300 ft. thick, and at depths between 6200- 8500 ft. The middle B chalk bench is the main production target. Despite over thirty years of production history at Silo Field, it is not well understood why only a few wells are top producers while neighboring wells have poor production rates. Our objective is to quantify relationships between geologic variables and production data, and to identify geologic factors that contribute the most to productive wells at Silo Field. Geologic variables analyzed include thickness, mineralogy, porosity, fracture intensity, and distance from faults. Correlations between production and geologic variables were determined by calibrating core and log data, creating cross-sections and maps, and using bivariate and multivariate analysis. Results from this study contribute to future Silo field development and understanding other Niobrara plays in the Denver basin like the nearby Wattenberg and Hereford fields in Colorado.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013