Date of Award:

5-2007

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

James P. Evans

Committee

James P. Evans

Committee

W. David Liddell

Committee

Carol M. Dehler

Abstract

The Nugget Formation in the Anschutz Ranch East field, northeast Utah and southwest Wyoming, provides an exceptional example of how primary eolian rock properties have a considerable influence on the style of structural deformation. Both new and existing subsurface data were integrated for an overall characterization of sedimentologic and diagenetic heterogeneities, which demonstrate relationships with different styles of structural compartmentalization in reservoirs. The Anschutz Ranch East field is a large asymmetric anticlinal trap in the Utah-Wyoming thrust belt. Three cores were analyzed in order to investigate brittle deformation in eolian facies: dune, apron, and interdune. Selected cores are located along the back limb of the main structure and are nearly perpendicular to the fold axis. Each eolian facies appears to have an associated style of deformation that generally occurs within this tectonic setting. Within the dune facies, deformation bands are the most common style of deformation, unless a fault is present; when faults are present open fractures and breccia occur. In the apron facies, open fractures are more prevalent; however deformation bands are still very frequent. The primary styles of brittle deformation observed in interdune facies are breccias and closed fractures. This relationship between facies and rheology also correlates with porosity. These results support a hypothesis that high porosity rocks tend to be weaker and develop deformation bands, while low porosity rocks have a greater strength and will deform brittlely.

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