Physical Properties of a Set of Sandstones, III: the Effects Of Fine Grained Pore Filling Material on Compressional Wave Velocity
Name
1985.14 Wilkens et al.pdf
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720.83 KB
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Author(s)
Wilkens, R. H.
Simmons, G.
Wissler, T. M.
Caruso, L.
Date Issued
1985
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1985-14
Abstract
We have used aspect ratio modeling to explain the measured compressional
wave velocities of twenty different dry sandstone samples with varying clay
contents at a single confining pressure of 0.5 kbar. Velocities of the sandstones
range between 3.1 km/sec and 5.7 km/sec. Measured porosities are between 6%
and 33%, clay contents between 2% and 30%. Pores were described using three
simple type classifications. The pore type distributions of the samples were
quantified by point counting polished impregnated thin sections using a scanning
electron microscope. A representative aspect-ratio was assigned to each of the
three categories of pore type. Velocities were modeled using these aspect ratios
weighted by the observed distribution of the porosity types. Agreement between
theoretical and measured velocities is generally within 10%. The modeling suggests
that the effects of clays in sandstone pores is to reduce the sample porosity without
reducing the non-framework (void + clay) volume. Thus, for a given porosity, clay rich
samples contain greater non-framework volume, which in turn lowers velocity. The
model derived from the dry measurements can be used to successfully approximate
empirical relationships for saturated samples of velocity-porosity-clay content taken
from the literature.
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