Constraining Fracture Systems with Seismic Attributes: Teapot Dome, Wyoming

Salamoff, Scotty¹, Dennis L. Harry², Jerry F. Magloughlin² (1) Chevron North America Exploration and Production, New Orleans, LA (2) Colorado State University, Fort Collins, CO

Seismic attributes in a 3-D data volume are used to map fracture trends in the Teapot Dome anticline in south-central Wyoming. This Late Cretaceous-Paleogene doubly-plunging anticline is located on the western edge of the Powder River Basin. Linear low-coherence seismic anomalies are well-developed on reflections from the tops of the Upper Cretaceous Frontier Formation, Lower Cretaceous Dakota Group, Jurassic Sundance Formation, Triassic Chugwater Group, and Pennsylvanian Tensleep Formation. These anomalies trend NE-SW, sub-parallel to the inferred maximum stress orientation during the Laramide orogeny and parallel to joints mapped at the surface. The coherence anomalies correlate with seismic wavelet phase anomalies and with decreases in average wavelet energy, maximum amplitude, and instantaneous frequency. The attribute anomalies are associated with two different waveform character changes compared to adjacent traces. The first is a decrease in period and amplitude. The second is formation of a doublet in the seismic pulse and an increase in period and decrease in amplitude. The changes in attributes and waveform character are consistent with scattering of seismic energy through < 30 m sub-vertical hinge-perpendicular fracture swarms. The seismic data resolution constrains the vertical offset of reflection horizons across the fracture swarms to be less than 10 m, indicating that the hinge-normal fractures are joints, small offset (sub-seismic) dip-slip faults, or strike-slip faults. The fracture systems extend from the surface to the base of the hanging-wall, indicating that fracture-induced reservoir partitioning is consistent throughout the hanging-wall. The study demonstrates that fracture systems in fault-related folds that have vertical displacements below the typical seismic resolution can be reliably imaged through seismic wavelet attribute analysis.