Deformation Band Networks in Mesozoic Eolian Sandstones of the Western United States and Offshore Hydrocarbon Reservoirs
Deformation bands are commonly associated with faults and flexure in porous, granular media. In the western United States, deformation bands are widely distributed in a number of Mesozoic eolian sandstones, particularly in association with monoclinal uplifts of the Colorado Plateau. Similar deformation bands have been observed in cores from deepwater hydrocarbon reservoirs, and there is some concern that permeability reduction in particularly dense band networks may negatively impact production. Predicting the spatial distribution of these networks is therefore critical. However, while the spatial characteristics of terrestrial bands can be mapped in great detail in 2 and sometimes 3 dimensions, the distribution of the deepwater bands is only known, at best, 1 dimensionally from core. Ultimately, prediction of the effect on reservoir permeability requires extrapolation from core data into a 3 dimensional characterization of band distribution.
Here, we examine deformation band populations at two sites in Utah: Buckskin Gulch (BSG) and Big Hole Fault (BFH). Both of these locations feature deformation band networks in the Navajo Sandstone with similar stratigraphic age and timing of deformation. However, the two locations differ in mode of deformation. Deformation bands at BSG occur in a thrust setting in the forelimb of the East Kaibab Monocline, while those at BHF are associated with an array of normal faults attributed to central flexure of the San Rafael Swell. Offshore, similar structures are often associated with hydrocarbon traps (albeit at a smaller scale) and therefore these locations serve as useful analogs. We apply spatial analysis techniques such as normalized correlation sum to deformation band populations at BSG and BHF, revealing fundamental differences. Ultimately, these characterizations may be useful in combining offshore core data with seismically interpreted structure to generate realistic 3D models of deformation band occurrence.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009