Talk Abstract:
Spatial Statistics of Permeability Data from Carbonate Outcrops
of West Texas and New Mexico and Implications for Fluid Flow
and Reactive Transport Modeling
James W. Jennings Jr.
The University of Texas at Austin
University Station, Box X
Austin, Texas, 78713-8924, USA
jenningsj@mail.utexas.edu
Joint work with Steven L. Bryant,
and Rashidul Hassan.
For
10 years the Carbonate Reservoir Characterization Research Laboratory
at The University of Texas at Austin has been collecting petrophysical
data from carbonate outcrops in West Texas and New Mexico to
advance knowledge in the geological, petrophysical, geostatistical,
and fluid flow aspects of this important class of fresh water
aquifer and hydrocarbon reservoir rocks. This presentation summarizes
the spatial statistics of permeability data collected from these
outcrops and the implications for fluid flow and reactive transport
modeling in analogous subsurface situations. In addition speculations
will be offered on the role of reactive transport in the origin
of some of the observed heterogeneity patterns.
The permeability data from these outcrops exhibit 2-5 orders
of magnitude variability, much of it occurring within distances
of a few feet or less in single rock fabric units. This short-range
variability is present in every outcrop and composes most of
the overall variance in each case. It has weak spatial correlation
that can be modeled with semivariograms having asymptotic power-law
behavior at small lags.
A variety of longer-range features are also observed including
(1) vertical trends within grainstone bodies, (2) vertical average
permeability contrasts between grainstone bodies, (3) 140-180
ft lateral periodicities within high frequency cycles, and (4)
lateral trends at scales from several hundred to several thousand
feet in high frequency cycles. The longer-range features compose
a smaller fraction of the overall variability and may require
careful analysis to detect.
Stochastic
models explore the fluid-flow effects of these heterogeneities.
Tracer and waterflood simulations demonstrate that the long-range
features can control overall large-scale displacement, even
though they compose much less than half of the overall variance.
Special attention when modeling them is encouraged. The small-scale
variability contributes to smearing of displacement fronts and
enhancement of larger scale effective permeability.
Slides
for the talk pdf
(8MB)
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1999-2000
Reactive Flow and Transport Phenomena
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