Rock
Physics
Rock Property Characterisation
To improve the understanding and characterisation of rock properties, particularly using geophysical sensing techniques, research is being done to understand the seismic response of fractured media, and to develop the use of compressional and shear-waves for better understanding of rock properties such as Poisson’s Ratio.
The Centre for Rock Characterisation (CRC) is
developing new tools for testing and monitoring changing
conditions of rock bolts by observing the effects of the full
seismic wave-field between in-situ bolts without the need for
their removal. The end product of this work will be the ability
to see changes between any two rock bolts, in the form of CT
scans - this project is being developed by a group of
geophysicists and rock mechanics. In addition, a new laser
system is to be installed which will provide an additional range
of rock properties not presently available to mining engineers.
Research Leader: Prof Brian Evans (B.Evans@curtin.edu.au).
Modelling Elastic
Properties of Fractured Reservoirs
A major effort of the rock physics group is directed towards
modelling attenuation, dispersion and frequency dependent
anisotropy of porous reservoirs permeated by aligned fractures.
In 2001-2003 we have developed a methodology of fluid
substitution in fractured reservoirs. In 2003-2006 we developed
a model for attenuation and dispersion of P-waves propagating
perpendicular to a periodic system of parallel planar fractures,
and validated this model with numerical simulations using a
poroelastic extension of the reflectivity method. These
simulations helped to extend the attenuation/dispersion model to
randomly spaced fractures and to oblique incidence.
More recently we developed a model for seismic attenuation and
dispersion caused by the presence of sparsely distributed finite
fractures in the porous reservoirs. The model is based on the
combination of Biot’s theory of poroelasticity with the ideas of
a multiple scattering theory. The current effort in this area is
focused on the deeper understanding of the implications of this
theory, and its extensions to
• Oblique incidence
• Shear waves
• Higher fracture densities
• Arbitrary aspect ratios.
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).
Simulation of Rock
Properties from Microstructure
A large effort of our group is directed towards modelling elastic properties of rocks from their microstructure. This approach has been made possible by recent advances in high-resolution X-ray imaging of rocks (down to 1 m) and by advances in computer technology which allow simulations on large 3D microtomographic images. This approach has a potential for a multitude of applications. Our current effort is mainly directed towards validation of existing theoretical effective-medium models, both for static and dynamic elastic properties.
For
static properties, our current approach utilises Finite-Element
simulations, and is focused on the validation of mixture models
for fractured and porous rocks, velocity-porosity models, models
of the effect of clay on the properties of sandstones. For
dynamic properties, the effort is aimed at the validation of the
models of local (squirt) and mesoscopic flow models. The
methodology here is based on the use of advanced
Finite-Difference algorithms. We do not aim to develop any new
numerical algorithms, and prefers to cooperate on this with
leading groups in 3D numerical simulations. However our
significant effort is applied to testing and validation of these
algorithms using a variety of exact solutions, as well as
adaptation of these algorithms to rock physics problems.
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).
Modelling of Properties of Rocks Saturated With Heavy Oil.
Rock physics for heavy oil is different from
rock physics for conventional fluids because its viscoelastic
rheology makes Gassmann theory and all its extensions, in
principle, inapplicable. We aim to develop an approximate
methodology for fluid substitution in heavy-oil reservoirs. The
methodology is based on one particular equivalent-medium
approach known as coherent potential approximation (CPA).
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).