Sedimentologic and diagenetic heterogeneities as an influence on structural deformation: Nugget Formation, Anschutz Ranch East field, Northeast Utah and Southwest Wyoming

Dustin Keele

Utah State University, Geology Department

Logan, Utah

[email protected]

Well-bore based studies of large amounts of core are crucial to develop an understanding of how sedimentologic and digenetic characteristics in eolian sandstone influence geomechanical processes. The Nugget Formation provides an example in how these primary heterogeneities can later act as preferred paths of structural deformation. Characterization of facies architecture, hierarchical nature of bounding surfaces, and digenetic features will demonstrate relationships with different types of structural compartmentalization.

The Anschutz Ranch East field is located in northeast Utah and southwest Wyoming, where the Jurassic Nugget Formation is the dominate hydrocarbon reservoir. This field has a vast amount of bore-hole data that are poorly synthesized and are scattered across the US. Core and wireline logs will be analyzed in order to develop a comprehensive reservoir description of the Nugget Formation.

Petrographic and statistical analysis of sedimentological attributes in thin sections obtained from core will include lithological descriptions, compositional contrasts in sediment, and texture parameters. Detailed analysis of core will also be conducted in order to determine facies, transport mechanisms, and bedform characteristics. The nature of diagenesis will be analyzed by x-ray diffraction; along with cathodolumenesce petrography for determination of cement histories and whether gouge-filled fractures have the same mineralology as authigenic clays. Petrographic and statistical analysis will also be preformed to determine if lithostatic loading affected sand grain boundaries.

A better understanding of how eolian sandstones deform and control fluid flow in a depleted hydrocarbon field will allow enhanced production in new fields, such as the Covenant field of central Utah.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid