--> Abstract: Compaction Localization—Rule or Exception During Sandstone Burial; #90063 (2007)

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Compaction Localization—Rule or Exception During Sandstone Burial?

 

Eichhubl, Peter1 (1) The University of Texas at Austin, Austin, TX

 

The localization of compaction into narrow zones has been documented in the field and reproduced in the laboratory. In the field, compaction localization is expressed as sets of tabular compaction bands. Their effect on the permeability structure, resulting in a horizontal permeability anisotropy of up to two orders of magnitude, has been documented through field observations and numerical models. Unclear is the significance of compaction localization for porosity reduction during burial compaction of sandstone reservoirs. Scanline surveys and porosity measurements of compaction bands in the Jurassic eolian Aztec Sandstone at Valley of Fire, NV, indicate that closely spaced compaction bands locally account for as much as 27% of bulk volume, resulting in up to 38% reduction in rock porosity. Compaction bands occur in two roughly orthogonal sets of 10-100 cm spaced subvertical bands, and a third set of bedding-parallel compactions bands. These widely spaced compaction bands occur throughout the stratigraphic section, though dominantly in the top third of the section. In addition, 0.5 to 1 cm spaced compaction bands, referred to as compaction lamellae, occur in addition, and parallel, to the widely spaced compaction bands. The occurrence of compaction lamellae appears confined to the vicinity of the Sevier Willow Tank thrust, and is attributed to deformation ahead of the advancing thrust sheet. Based on these current results it is suggested that compaction localization is the dominant mode of porosity reduction under specific stress loading conditions typically associated with tectonic processes.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California