structural geology, propagation mechanics and - Stanford School of ...

Introduction
Some brittle structures in rock act to enhance and channel fluid flow, others to
impede and compartmentalize it. Commonly, structures of both types interact with and
overprint each other to form complex fabrics that exert a dominating influence on flow in
subsurface aquifers and reservoirs, even those endowed with high intrinsic permeability
such as porous sandstone. Understanding the distribution, geometry and flow properties
of these structural fabrics is therefore vital to optimal resource production and
management. Unfortunately, data on the attributes of these fabrics—whether from 3-D
seismic surveys, borehole geophysical logs, pump tests and production data, or core
analysis—are generally limited and may be virtually nonexistent for small-scale
structures. One approach to addressing this problem is to study exhumed analog aquifers
and reservoirs, where structures and fabrics can easily be observed (at least in 2-D),
sampled and analyzed. The ultimate goal of such studies is to develop insights and tools
for forecasting the presence and influence of structures in the subsurface based on limited
hard data.
That has been the theme of an ongoing, decade-long research project undertaken by
David Pollard and Atilla Aydin with funding from the U.S. Department of Energy, Office
of Basic Energy Sciences—Structural Heterogeneities and Paleo Fluid Flow in an
Analog Sandstone Reservoir. My thesis work fits into this larger research initiative, just
as my topic—deformation bands and, more specifically, compaction bands—fits into the
framework of structures that did demonstrably impact paleo fluid flow in the Aztec
sandstone and are now breathtakingly exposed in the aptly named Valley of Fire of
southeastern Nevada. My effort follows three earlier Stanford dissertations that also took
shape from the colorful outcrops of the Valley of Fire: Fluid flow and chemical alteration
in fractured sandstone (W.L. Taylor, 1999); Structure and hydraulics of brittle faults in
sandstone (R.D. Myers, 1999); and Structural evolution, petrophysics and large-scale
permeability of faults in sandstone, Valley of Fire, Nevada (E.A. Flodin, 2003).
This dissertation focuses on the oldest structural fabric components present in the
Aztec sandstone—compaction bands—and endeavors to comprehend what they are, why
they formed, and how they influence bulk permeability and fluid flow. In essence, I take
a broad look at a specific structural phenomenon, one which physical logic dictates is
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