Abstract of the paper ``The elastic coefficients of double-porosity
models for fluid transport in jointed rock,'' with H. F. Wang
Phenomenological equations (with coefficients to be determined by specified
experiments) for the
poroelastic behavior of a dual porosity
medium are formulated and the coefficients
in these linear equations are identified.
The generalization from the single porosity
case increases the number of independent
coefficients for volume deformation from three to six for
an isotropic applied stress.
The physical interpretations are based upon
considerations of different temporal and spatial scales.
For very short times, both matrix and fractures behave
in an undrained fashion.
For very long times, the double porosity medium
behaves as an equivalent single porosity medium.
At the macroscopic spatial level, the
pertinent parameters (such as the total compressibility) may
be determined by appropriate field tests.
At an intermediate or mesoscopic scale
pertinent parameters of the rock matrix can be determined
directly through laboratory measurements on core,
and the compressibility can be measured for
a single fracture.
All six coefficients are determined from the three poroelastic
matrix coefficients and the fracture compressibility
from the single assumption that the solid grain
modulus of the composite is approximately the same as
that of the matrix for a small fracture porosity.
Under this assumption, the total compressibility
and three-dimensional storage compressibility of the
composite are the
volume averages of the matrix and fracture contributions.
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