Integrated seismic and geologic analysis of high density fracture zones within the Niobrara Formation in Moffat County, NW Colorado

Vivian Lin, J. Frederick Sarg, and Stephen Sonnenberg

The Niobrara Formation is a self-sourced resource play with key production occurring in 'sweet spots' that may extend downdip off structure, unlike in conventional reservoirs. Mapping the location and orientations of high density fracture zones is key to identifying these productive areas in tight petroleum systems. This study integrates a 3D seismic interpretation with a well log analysis in order to determine how high density fracture zones in the Niobrara relate to facies distribution and regional structures (particularly from the Laramide compressional and Neogene extensional tectonics). Maps of high density fracture zones were produced from seismic attribute analysis including dip azimuth and curvature. The high density fracture zone maps were then compared to local structures to determine whether regional tectonics could account for the location and orientations of all or a subset of the high density fracture zones. The fracture zone maps were also compared to facies distribution maps, which were produced from sequence stratigraphic analysis of seismic and well log data. The results of this study conclude that tectonics, facies, brittleness, and current stress regimes all contribute to the location, orientations, and density of the fracture zones within the Niobrara. It is suspected that other processes (such as hydrocarbon generation and the solution of evaporites) also play a role in fracture development. This integrated approach using seismic and well log analyses can be applied to explore other trends within the Sand Wash basin and nearby regions. The relationships identified in this study between facies, brittleness, current stress regimes and regional structure allow for better identification and prediction of 'sweet spots'. In areas where good seismic and well log data are available, the same procedures conducted in this study may be applied to produce high density fracture zone, structural, and facies maps that may then be analyzed to determine the most prospective locations. Even in areas where seismic and well log data may be limited, these relationships permit exploration play trends to be high-graded for further data acquisition and analyses.

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