Abstract of the paper ``Volume Averaging, Effective Stress Rules, and
Inversion for Microstructural Response of Multicomponent Porous Media''
with S. R. Pride
A general volume-averaging technique
is used to derive equations satisfied by the average scalar
stresses and strains
in multicomponent porous rock. The resulting equations are
combined with general thought experiments to produce the
effective-stress rules that determine the volumetric changes
of the rock induced by changes in the confining and fluid
pressures.
The composite porous material specifically treated is an
isotropic mixture of
two Gassmann materials.
Two distinct cases are considered depending on whether
the grains at the interface between
the Gassmann materials are either 1) welded together
(no ``cracks''
can open between the two constituents) or 2) nonwelded
(cracks can open).
The effective-stress laws determine not only the overall
volumetric changes of a given sample ({\it i.e.,} changes
in sample volume, total pore volume, and fluid-mass content),
but determine as well the changes within each Gassmann
component individually. This additional level of detail achieved in the
analysis is referred to as the inversion for the microstructural response.
In the nonwelded case, the effective-stress law relating the
variation of crack porosity with macroscopic changes in
confining
and fluid stress can be used to determine optimum
strategies for increasing fracture/crack porosity with
applications
to reservoir production analysis.
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