Curtin University is widely recognised for its achievements in applied research that is firmly focused on solving real-world problems.
Underpinning our research endeavours are strong partnerships with industry, business and government, which result in outcomes that greatly benefit the broader community locally, nationally and globally.
Theoretical and experimental rock physics
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 cfmect ratios
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.
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.
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.
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).
Geophysical imaging and reservoir characterisation
The department is involved in the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), one of the world’s leading collaborative research organisations focused on carbon dioxide capture and geological sequestration (geosequestration, carbon capture and storage, or CCS). The Curtin node of CO2CRC is involved in research, development and testing of geophysical technologies for monitoring the processes of carbon dioxide containment within the sub-surface. In particular, researchers from the department of exploration geophysics are involved in development and deployment of integrated geophysical technology for monitoring CO2 storage in the world-leading Otway demonstration project in south-western Victoria.
AVO analysis and inversion are widely used in characterisation of hydrocarbon reservoirs. Seismic anisotropy is known to have considerable effect on amplitudes. This effect is often ignored in AVO studies. This project aims to extract information about polar anisotropy of shales and azimuthal anisotropy of sand reservoirs from well logs, VSP and surface seismic data, and apply this knowledge to improve the accuracy and reliability of amplitude-based reservoir characterisation.
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.
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.
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.
Mining and environmental geophysics
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 cfmects of these problems exists with researchers from the University of Toronto (Canada) and University of Uppsala (Sweden).
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.
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.
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.