Exploration Geophysics
The major areas of research are:
Contact: Associate Professor Bruce Hartley (B.Hartley@curtin.edu.au) or Student Information (studentinfo@geophy.curtin.edu.au).
More information is also available at the following website: www.geophysics.curtin.edu.au
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
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Oblique incidence
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Shear waves
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Higher fracture densities
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Arbitrary aspect ratios.
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).
Seismic Signatures of Patchy Saturation
Another major effort of the group is focused on the study of the effects of patchy saturation on seismic signatures. The main objective is to quantify the effect of random spatial distribution of fluid patches. The approach is based on the general theory of heterogeneous poroelasticity developed in 2003-2005. The aim of the current effort is to build a general model for elastic properties of partially saturated rock with a given statistical distribution of fractures and with arbitrary contrast between the properties of the two fluids (e.g., gas and liquid). Future work will also involve analysis of the effect of self-similar distribution of fluid patches. We are also developing a series of fluid injection experiments with X-ray and ultrasonic control to validate theoretical findings. This research is partially funded by the ARC Discovery Project Seismic response of partially saturated petroleum reservoir zones: towards quantitative recovery monitoring.
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).
Velocity-Stress Relationships (for time-lapse seismic)
One of the major issues in planning and quantitative interpretation of time-lapse seismic data is quantification of the pressure and stress effects on seismic velocities. To this end we are developing theoretical models of rock deformation. In particular, we have developed a method to assess the effect of rock heterogeneity on effective stress coefficients and showed that the addition of a tiny amount of very soft material may significantly affect effective stress coefficients. This has been demonstrated for an idealised concentric spherical geometry. Currently we are examining the magnitude of this effect for more realistic geometries.
A related effort is to assess the effect of core damage of velocity-stress relationships measured in the laboratory. To study this effect we are developing a method to compare laboratory measured velocities with sonic log measurements for different types of rocks.
Research Leader: Prof Boris Gurevich (B.Gurevich@curtin.edu.au).
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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).
Greenhouse Gas (CO2) Sensing
New knowledge is being obtained into how greenhouse gases in general, and mixed quantities of CO2 and methane in particular, dissolve in water. Methods for remotely distinguishing water from carbon dioxide have been published. Such knowledge allows the ability to monitor and quantify the amount of CO2 injected during sequestration processes, and will allow the future dependable management of CO2 injection operations through controlled verification of the CO2 storage process. Supercritical CO2 research is being conducted in a large pressure chamber into which CO2 is injected and monitored using both 3D and seismic tomography methods. In addition, research into using the 3D seismic method for monitoring the injection process at Australia’s first injection test site is ongoing. Collaborative work is being done with the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) researchers at University of Adelaide and Melbourne, as well as researchers in Delft University (Holland) and Montana (US).
Research Contact: Prof Brian Evans (B.Evans@curtin.edu.au).
Physical Modelling of Reservoirs
Fluid flow through reservoir fractures and heterogeneities often cause reservoir simulators to fail to adequately predict oil and gas production. In addition, it is often very difficult to develop new algorithms without knowledge of the reservoir characteristics in the first place. The Curtin Physical Modelling laboratory builds models of geological structure and records ultrasonic data over the models to provide simulated field data for use with standard or new algorithms. In addition, the laboratory has a pressure chamber in which models may be pressured to simulate conditions underground. With visiting researchers from Montana University (US), techniques are developing to allow 3D and cross-well tomographic recording of models.
Research Leader: Prof Brian Evans (B.Evans@curtin.edu.au).
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Reservoir Imaging
Technologies have been developed over the years to understand how fluid flows through reservoirs during production. However, where karst or near-surface basalt conditions occur, it becomes impossible to image the reservoirs due to excessive seismic scattering. A new method has been developed and patented, in which a low cost horizontal well is drilled beneath the overburden, to allow the insertion of a seismic cable and consequent recording of seismic data, to produce an image of the reservoir for the first time. An initial experiment will be performed over methane coal fields in Queensland in an attempt to demonstrate this as a feasible solution to imaging reservoirs beneath complex karst and basalt topography.
Research Leader: Prof Brian Evans (B.Evans@curtin.edu.au).
Reversed Time Acoustics and Virtual Source Imaging
A low cost low power continuous vibratory system has been developed for seismic imaging applications over reservoirs. In addition, methods of time reversed acoustics have been successfully applied to imaging targets beneath strongly scattering near-surface layering. These methods are soon to be applied in field tests to assist the monitoring of injected CO2 and methane production. The use of continuous sources holds promise of considerably improving the precision of seismic measurements. Changes in travel time of less than a micro-second can be achieved and will lead to measurements of frequency dependent velocity measurements of fluids in porous media. Changes in the velocity dependent dispersion will lead to the characterisation of fluids and of reservoir conditions as fluids are injected or withdrawn from reservoirs.
Some work on time reversed acoustics was done in collaboration with the Laboratoire Ondes et Acoustique in Paris. This has developed now to laboratory and numerical simulation of the application of time reversed acoustics in simulating sources below surface multi-scattering layers in a method known in geophysics as the Virtual Source Method.
Research Leader: Associate Prof Bruce Hartley (B.Hartley@curtin.edu.au).
Effects of Shale/Sand Anisotropy on AVO-Based Reservoir Characterisation
Intrinsic shale anisotropy in combination with often present stress induced reservoir sand anisotropy presents a challenging situation for reservoir characterisation from seismic data. Research in this area includes analysis of the magnitude of anisotropy, separation of the sand from shale anisotropy contribution to AVO signature and fracture characterisation from borehole and surface seismic measurements.
Research Leader: Dr Milovan Urosevic (M.Urosevic@curtin.edu.au).
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Fracture Orientation from Anisotropy Measurements
Methods of finding orientation of symmetry axes of the medium from its elasticity parameters have been developed. Knowledge of the symmetry axes can aid in finding the orientation of fractures in the medium. However, the measurements of the elasticity parameters in seismology is prone to large errors. The scope of the current research is to adapt the developed methods to deal with these errors.
Research Leader: Dr Andrej Bona (ABona@curtin.edu.au).
Tomography in Heterogeneous Media
One of the main problems with imaging in heterogeneous media is the fact that the rays are generally curved. Imaging methods based on generalised Radon transform that takes into account the curved rays are being developed.
Research Leader: Dr Andrej Bona (A.Bona@curtin.edu.au).
Sea-bed Electromagnets
The use of electromagnets in mine site delineation has been a standard feature of mineral geophysics in the past but the application to sensing changes in oil field fluids is a relatively new application. Most of the activity in this area has been by groups historically involved in Magneto-telluric methods. Curtin’s long involvement in developing state-of-the-art instrumentation, signal processing analysis and interpretation of Transient Electromagnetics (TEM) for mineral exploration in geologically complex environments provides a different perspective upon the possible acquisition configurations and interpretation methodology for sub-sea EM for oil/gas.
Research Leaders: Dr Anton Kepic (A.Kepic@curtin.edu.au) and Dr Brett Harris (B.Harris@curtin.edu.au).
Ore-Body Delineation
As mines become deeper and most undiscovered mineral deposits lie beneath a complex surface geology a need to see deeper with more clarity arises. So the state-funded Centre for High Definition Geophysics (CHDG) extends current seismic technologies to provide 2D and 3D images of ore deposits with greater detail and contrast than ever before - and we’ve only just started! Areas of current and future research are: novel acquisition and signal processing techniques yielding a higher signal-to-noise ratio and an increased frequency content; robust and accurate static corrections in difficult conditions such as highly variable regolith and velocity inversion; modified swath and 2.5 dimensional crooked-line acquisition and processing; borehole seismic techniques for hard rock exploration such as 2D and 3D vertical seismic profiling (VSP; inversion for rock properties and interpretation; multi-component seismic data for geotechnical information. Collaboration on theoretical aspects of these problems exists with researchers from the University of Toronto (Canada) and University of Uppsala (Sweden).
Research Leaders: Dr. Anton Kepic (A.Kepic@curtin.edu.au) and Dr. Milovan Urosevic (M.Urosevic@curtin.edu.au).
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Seismoelectric Methods
Seismoelectric methods may provide the ability to directly infer the permeability of porous media, and can complement other geophysical data. Although the effect has been studied for decades seismoelectric effects are difficult to measure, requiring great care and skill in collecting and analysing electrical data. Curtin is at the forefront in trialling this method for application to water resource definition and management. This work is in close collaboration with researchers from the University of New Brunswick. In addition, further work is required to develop a reliable means to perform laboratory measurements in small-scale physical modelling and sample measurements.
Research Leader: Dr Anton Kepic (A.Kepic@curtin.edu.au).
Future Water Storage Options
Managed aquifer recharge (MAR) and aquifer storage and recovery (ASR) have become important tools for modern groundwater management. They offer the possibility of storing and retrieving large volumes of highly treated waste water that might otherwise be discharged to the Ocean. However these relatively new water management tools require a much higher standard of investigation and monitoring, especially in the near well environment. Curtin University Department of Exploration Geophysics is developing a set of very high resolution geophysical methods that may be used to help assess, design and monitor MAR and ASR projects. These include 3D seismic reflection, time lapse vertical seismic profiling, radar and time lapse geophysical logging.
Research Leader: Dr Brett Harris (B.Harris@curtin.edu.au).
Geophysical Instrumentation
Curtin currently supplies very low noise magnetic coil sensors and high-to-medium powered transmitters to several Australian explorers using the Transient Electromagnetic (TEM) method. Considerable in-house expertise on optimising electronic design for magnetic sensors exists. Curtin has strong ties with industry and a reputation for providing solutions that meet and anticipate industry needs. Current and future projects include improving and evaluating seismic sources for hard-rock seismic exploration, hybrid coil/fluxgate magnetometers, and sensors for seismic land-streamers.
Research Leader: Dr Anton Kepic (A.Kepic@curtin.edu.au).