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Tassone D.R.,University of Adelaide | Holford S.P.,University of Adelaide | Duddy I.R.,Geotrack International | Green P.F.,Geotrack International | Hillis R.R.,Deep Exploration Technologies Cooperative Research Center
AAPG Bulletin | Year: 2014

In prospective basins affected by exhumation, uncertainty commonly exists regarding the maximum burial depths of source, reservoir, and seal horizons. One such basin is the Otway Basin, an important gas province in southeastern Australia, which has witnessed several exhumation events. Here, we present estimates of net exhumation magnitudes for 110 onshore and offshore petroleum wells based on the sonic transit time analyses of Lower Cretaceous fluvial shales. Our results show significant post-Albian net exhumation in the eastern onshore Otway Basin (>1500 m [̃4920 ft]) and a generally minor net exhumation (<200 m [̃655 ft]) elsewhere in the Otway Basin, consistent with estimates based on thermal history data. The distribution of net exhumation magnitudes in relation to mid-Cretaceous and Neogene compressional structures indicates that exhumation was dominantly controlled by short-wavelength basin inversion driven by plate-boundary forces. Deeper burial coupled with high geothermal gradients in the onshore eastern Otway Basin and along the northern basin margin during the early Cretaceous have rendered Lower Cretaceous source rocks mostly overmature, with any remaining hydrocarbons from the initial charge likely to be trapped in tightly compacted reservoirs and/or secondary (fracture-related) porosity. However, the embrittlement of these reservoirs during their deeper burial may present opportunities for the development of low-permeability plays through hydraulic fracturing where smectite clay minerals are illitized. Source rocks at near-maximum burial at present day are at temperatures suitable for gas generation, with key controls on prospectivity in these areas including the sealing potential of faulted traps and the relationship between charge and trap development. ©2014. The American Association of Petroleum Geologists. ©2014. The American Association of Petroleum Geologists. All rights reserved. Source


Munoz H.,Deep Exploration Technologies Cooperative Research Center | Munoz H.,University of Adelaide | Taheri A.,University of Adelaide | Chanda E.K.,University of Adelaide
Rock Mechanics and Rock Engineering | Year: 2016

A non-contact optical method for strain measurement applying three-dimensional digital image correlation (3D DIC) in uniaxial compression is presented. A series of monotonic uniaxial compression tests under quasi-static loading conditions on Hawkesbury sandstone specimens were conducted. A prescribed constant lateral-strain rate to control the applied axial load in a closed-loop system allowed capturing the complete stress–strain behaviour of the rock, i.e. the pre-peak and post-peak stress–strain regimes. 3D DIC uses two digital cameras to acquire images of the undeformed and deformed shape of an object to perform image analysis and provides deformation and motion measurements. Observations showed that 3D DIC provides strains free from bedding error in contrast to strains from LVDT. Erroneous measurements due to the compliance of the compressive machine are also eliminated. Furthermore, by 3D DIC technique relatively large strains developed in the post-peak regime, in particular within localised zones, difficult to capture by bonded strain gauges, can be measured in a straight forward manner. Field of strains and eventual strain localisation in the rock surface were analysed by 3D DIC method, coupled with the respective stress levels in the rock. Field strain development in the rock samples, both in axial and shear strain domains suggested that strain localisation takes place progressively and develops at a lower rate in pre-peak regime. It is accelerated, otherwise, in post-peak regime associated with the increasing rate of strength degradation. The results show that a major failure plane, due to strain localisation, becomes noticeable only long after the peak stress took place. In addition, post-peak stress–strain behaviour was observed to be either in a form of localised strain in a shearing zone or inelastic unloading outside of the shearing zone. © 2016 Springer-Verlag Wien Source


Munoz H.,Deep Exploration Technologies Cooperative Research Center | Munoz H.,University of Adelaide | Taheri A.,University of Adelaide | Chanda E.K.,University of Adelaide
Rock Mechanics and Rock Engineering | Year: 2016

To reliably estimate drilling performance both tool–rock interaction laws along with a proper rock brittleness index are required to be implemented. In this study, the performance of a single polycrystalline diamond compact (PDC) cutter cutting and different drilling methods including PDC rotary drilling, roller-cone rotary drilling and percussive drilling were investigated. To investigate drilling performance by rock strength properties, laboratory PDC cutting tests were performed on different rocks to obtain cutting parameters. In addition, results of laboratory and field drilling on different rocks found elsewhere in literature were used. Laboratory and field cutting and drilling test results were coupled with values of a new rock brittleness index proposed herein and developed based on energy dissipation withdrawn from the complete stress–strain curve in uniaxial compression. To quantify cutting and drilling performance, the intrinsic specific energy in rotary-cutting action, i.e. the energy consumed in pure cutting action, and drilling penetration rate values in percussive action were used. The results show that the new energy-based brittleness index successfully describes the performance of different cutting and drilling methods and therefore is relevant to assess drilling performance for engineering applications. © 2016 Springer-Verlag Wien Source


Schnaidt S.,Deep Exploration Technologies Cooperative Research Center | Schnaidt S.,University of Adelaide | Heinson G.,University of Adelaide
Geophysical Journal International | Year: 2015

Uncertainty estimation is a vital part of geophysical numerical modelling. There exist a variety of methods aimed at uncertainty estimation, which are often complicated and difficult to implement. We present an inversion technique that produces multiple solutions, based on bootstrap resampling, to create a qualitative uncertainty measure for 2-D magnetotelluric inversion models. The approach is easy to implement, can be used with almost any inversion code, and does not require access to the inversion software's source code. It is capable of detecting the effect of data uncertainties on the model result rather than just analysing the effect of model variations on the model response. To obtain uncertainty estimates for an inversion model, the original data set is resampled repeatedly and alternate data set realizations are created and inverted. This ensemble of solutions is then statistically analysed to determine the variability between the different solutions. The process yields interpretable uncertainty maps for the inversion model and we demonstrate its effectiveness to qualitatively quantify uncertainty in synthetic model tests and a case study. © The Authors 2015. Published by Oxford University Press on behalf of The Royal Astronomical Society. Source


Fisher L.,CSIRO | Fisher L.,Deep Exploration Technologies Cooperative Research Center | Gazley M.F.,Barrick Australia Pacific | Gazley M.F.,Victoria University of Wellington | And 5 more authors.
Geochemistry: Exploration, Environment, Analysis | Year: 2014

Portable X-ray fluorescence (pXRF) technology can be used to collect large amounts of multi-element data rapidly at relatively low cost and has been widely embraced within the minerals industry. However, to date, it has been difficult to compare data-sets collected by different users or at different times because there is no standardized approach to the collection of these data. The absence of information on standardization and calibration procedures raises concerns about a lack of internal consistency within these data-sets and precludes comparison of different data-sets. This paper seeks to address this issue by developing a workflow for the collection of pXRF data in an exploration or mining setting. Two case studies highlight the robustness and possible applications of pXRF data collected following QA/QC protocols. A good correlation between conventional laboratory analyses and pXRF data is demonstrated through comparison of analysis methods for a drill-hole at the Plutonic Gold Mine, Western Australia, and fine-scale lithostratigraphic variation is recognized in pXRF data collected on grade control pulps from a drill fan at the Agnew Gold Mine, Western Australia. The Agnew data precision is sufficient to distinguish alteration signals from background lithology, and to discern which alteration signals are associated with gold mineralization. © 2014 AAG/The Geological Society of London. Source

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