Identifying Geologic Variables Controlling Production from the Niobrara Formation at Silo Field, Laramie County, Wyoming

Carrie Welker, Lisa Stright, and Tom Anderson

The Niobrara Formation, deposited in the Cretaceous Western Interior Seaway, is an interbedded source-rock shale and low-porosity limestone formation extending from Montana to New Mexico. Silo Field, located in the Denver-Julesburg Basin in Laramie County, Wyoming has been producing from the Niobrara since 1981. Cumulative production to date is 10.5 MMBO and 9,348 MMCFG. At Silo Field, the Niobrara consists of the lower Fort Hayes Limestone Member and the upper Smoky Hill Member, which contains three limestone benches named A, B, and C; the B bench being the main production target. Despite a long production history and comprehensive well data, it is not well understood why neighboring wells can have very different production rates. Our objective is to identify geologic factors that contribute to the most productive wells or groups of wells ("sweet spots") at Silo Field. We will present the correlation between production data and geologic parameters determined from core, well logs, cross-sections and maps. These parameters include mineralogy, distance from faults, fracture intensity, structure, interval thickness, and porosity. We will interpret and correlate geologic characteristics of the main production target, the B bench, to evaluate changes in vertical and lateral heterogeneity. Our goal is to build a predictive model of spatial and stratigraphic heterogeneity for Silo field that considers geologic parameters and apply that model to other Denver-Julesburg fields like the Hereford and Wattenberg Fields in Colorado. Understanding which geologic variables are most important in defining "sweet spots" will aid future reservoir development in shale oil plays.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012