Fracture Pattern Analysis using FMI Logs of the Tensleep Formation, Teapot Dome, Wyoming
Schwartz, Bryan C.1,2, Wilson, Thomas H.1,2, and Smith, Duane H.1
1Department of Energy, National Energy Technology Laboratory,
2West Virginia University, Department of Geology and Geography
This study presents a detailed analysis of fracture distributions and orientations in the Tensleep Formation along the axis of the Teapot Dome in northeastern Wyoming. Oil production from the Tensleep is restricted to a fault bounded culmination located on the southern part of the dome. 3D seismic data portray the major structural subdivisions of this basement cored uplift. The characteristics of fracturing in the Tensleep are inferred from FMI logs in wells distributed along the north-south trending axis of the dome. The Pennsylvanian aged Tensleep Formation is approximately 250 feet thick in the area. The formation was deposited in an aeolian sand/ sabkha evaporite environment and consists of a series of sand and dolomite intervals. Stereonets and rose diagrams of open fractures in the Tensleep reveal that fractures can be grouped predominantly into two clusters: one with vector mean strike of N71W and a second with vector mean strike of N22W. However, examination of fracture orientations in the lithologic subdivisions of the Tensleep reveals considerable variability from one unit to the next.
The Tensleep has relatively low permeability, averaging about 30 mD. Oil production is largely controlled by fracture connectivity and permeability. This study will be used to develop multilayer models of fracture properties. The National Energy Technology Laboratory code FRACGEN will be used to extend those descriptions into the surrounding region. Multiple realizations of possible fracture distributions will be derived in this study. These models will eventually serve as the basis for flow simulations of oil production.