--> Abstract: Structural, Lithological, and Regional Tectonic Controls from P-Wave Azimuthal Anisotropy: Casper Arch, Wyoming, by R. Duke Cooley and Eric A. Erslev; #90078 (2008)
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Structural, Lithological, and Regional Tectonic Controls from P-Wave Azimuthal Previous HitAnisotropyNext Hit: Casper Arch, Wyoming

R. Duke Cooley and Eric A. Erslev
Geosciences, Colorado State University, Fort Collins, CO

Subsurface fracture networks can enhance/retard subsurface fluid flow; therefore characterization of fractures is important to predict permeability anomalies in petroleum reservoirs. Direct fracture characterization is currently limited to core/logs from wells or outcrop data. New seismic processing methods that calculate seismic velocity Previous HitanisotropyNext Hit may help to characterize fractures if their signatures can be deciphered from that of other aligned crustal heterogeneities. This project compares an anisotropic 3D seismic data set with field data on structural fabrics from nearby analog structures to help interpret seismic Previous HitanisotropyNext Hit.

A 3D seismic volume of an anticlinal structure was mapped for variations in azimuthal Previous HitanisotropyNext Hit at multiple stratigraphic and structural positions. Azimuthal variations are observed at two distinct lithological boundaries. A regional Previous HitanisotropyNext Hit (110-130°) is observed with maxima in undeformed areas above the Frontier. The Frontier-Tensleep section exhibits a general 120° azimuth and the Tensleep-Basement section exhibits a general 20° azimuth in the backlimb and crest. Azimuths vary, more E-W, near the fault and in the synclinal hinge.

In nearby analog structures, fracture orientations at different stratigraphic levels within the same structural position were similar indicating Previous HitanisotropyNext Hit variations at lithological boundaries are related to sedimentary structures/composition and not fracturing. Azimuthal deviations at structural features, Previous HitanisotropyNext Hit magnitude variations paralleling faults, and surface fractures indicate that structural mechanisms related to Laramide compression are responsible for local variations in Previous HitanisotropyNext Hit azimuths. The regional Previous HitanisotropyNext Hit (110-130°) indicates a regional cause of Previous HitanisotropyTop. This azimuth matches a secondary joint orientation observed in the field and the present day stress orientation.


AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas