No description available.

No description available.

The supergene mineralogy and geochemistry of numerous deposits in the Cobar region have been systematically explored in this study, with a particular focus on the oxidised zones of the Endeavour, Mineral Hill and New Cobar orebodies. A recurring pattern was identified in the oxidised mineral assemblages of the region, characterised by a multiple-stage paragenesis. Comprehensive geochemical modelling based on equilibrium processes was undertaken to elucidate the geochemical conditions under which the various assemblages formed. The exercise was extended in a series of experiments concerning the interaction of ground and vadose waters with secondary mineral species. This has led to a self-consistent geochemical exploration model for deposits in the Cobar basin. The model promises to be very useful for exploration in highly weathered terrains, particularly where the deposits lack significant surface expression. A similar approach may be relevant to exploration in other areas around Australia and world-wide. / Doctor of Philosophy (PhD)

Electrical imaging of groundwater that interacts with surface watercourses provides detail on the extent of intervention needed to accurately manage both resources. It is particularly important where one resource is saline or otherwise polluted, where spatial quantification of the interacting resources is critical to water use planning and where losses from surface waterways need to be minimized in order to transport water long distances. Geo-electric arrays or transient electromagnetic devices can be towed along watercourses to image electrical conductivity (EC) at multiple depths within and beneath those watercourses. It has been found that in such environments, EC is typically related primarily to groundwater salinity and secondarily to clay content. Submerged geo-electric arrays can detect detailed canal-bottom variations if correctly designed. Floating arrays pass obstacles easily and are good for surveying constricted rivers and canals. Transient electromagnetic devices detect saline features clearly but have inferior ability to detect fine changes just below beds of watercourses. All require that water depth be measured by sonar or pressure sensors for successful elimination of effects of the water layer on the data. The meandering paths of rivers and canals, combined with the sheer volume of data typically acquired in waterborne surveys, results in a geo-referencing dilemma that cannot be accommodated using either 2D imaging or 3D voxel imaging. Because of this, software was developed by the author which allows users to view vertical section images wrapped along meandering paths in 3D space so that they resemble ribbons. Geo-electric arrays suitable for simultaneous imaging of both shallow and deep strata need exponentially spread receiver electrodes and elongated transmitter electrodes. In order to design and facilitate such arrays, signed monopole notation for arrays with iv segmented elongated electrodes was developed. The new notation greatly simplified generalized geo-electric array equations and led to processing efficiency. It was used in the development of new array design software and automated inversion software including a new technique for stable inversion of datasets including data with values below noise level. The Allen Exponential Bipole (AXB) array configuration was defined as a collinear arrangement of 2 elongated transmitter electrodes followed by receiver electrodes spaced exponentially from the end of the second transmitter electrode. A method for constructing such geo-electric arrays for use in rivers and canals was developed and the resulting equipment was refined during the creation of an extensive set of EC imaging case studies distributed across canals and rivers of the Australian Murray- Darling Basin. Man made and natural variations in aquifers connected to those canals and rivers have been clearly and precisely identified in more than 1000 kilometres of EC imagery.

The sustainability of groundwater resources is important for the environment, the economy and communities where surface water is scarce. It is a hidden resource, but additional information can be extracted by combining groundwater measurements and lithological information with groundwater flow equations in groundwater models. The models convert data and knowledge about the groundwater systems into information, such as relative inflow and outflow rates and water-level predictions that can be readily understood by groundwater managers. ¶ The development of models to effectively inform groundwater management policies is, however, a complex task that presents a fundamental scientific challenge. This thesis presents methods and results for water balances calculated using groundwater flow models. Groundwater flow modelling methods and approaches are discussed, and their capabilities and limitations are reviewed. Two groundwater systems are studied for the Great Artesian Basin (GAB) and for the irrigation area near Bowen, Queensland. Three approaches to water balance modelling are applied in comprehensive model-development frameworks that take into account model objectives, data and knowledge availability and sensitivity analysis techniques. The three models show numerical methods of increasing complexity. The Bowen study area is well-suited to the least-complex method because data collection has been a priority there. As a contrast, the GAB is a large, poorly-monitored basin for which more knowledge of the groundwater system can be gained from its simulation by the steady state and transient groundwater flow models. The Bowen impact assessment model calculates dynamic historical water balances. The GAB aquifer models are high-complexity representations of the groundwater system that include predicted responses of the system to changes in hydrological conditions. These are comprehensive and well-documented attempts to model these systems. They provide a platform for scenario investigation and future improvements. ¶ Darcy’s Law was used in a GIS (Geographic Information System) to calculate dynamic water balances for an aquifer near the Queensland town of Bowen. This is the first time this approach has been applied to generate a complete groundwater balance. Over the period 1989-1997 the model estimates average total inflows to be 87 % groundwater recharge by rainfall and irrigation return flow, 12 % river recharge and 1 % inflow across the study area boundary. Outflows are estimated to be 66 % evapotranspiration, 28 % water bore discharge, 4 % discharge to the ocean and 2 % groundwater loss to rivers. Analyses show that evapotranspiration is the most uncertain parameter value. The GIS method was found to be useful for calculating water balances more accurately than analytical methods, because of their simplifying assumptions, and less time consuming than the more complex numerical models developed for the GAB aquifer. ¶ For the GAB, a steady state numerical model was developed and tested and predictive scenarios were run. The purpose of this modelling was both to gain a better understanding of the water balance of the GAB and to provide a tool that could predict water level recoveries under different bore rehabilitation scenarios. The model complexity is greater than in any previous numerical groundwater model of the GAB. In particular, the model uses more data, extends over a larger area and uses a generally finer discretisation than previous models. For the nearest surface artesian aquifer in 1960 the model estimates total inflows to be 60 % groundwater recharge and 40 % diffuse vertical inter-aquifer leakage. The model estimates outflows to be 53 % diffuse vertical leakage, 43 % water bore discharge, 3 % spring discharge and 1 % discharge to the ocean. Analyses show that the model is most sensitive to changes in horizontal hydraulic conductivity and recharge. The model-predicted heads match field measurements with a Scaled RMS error of 0.8 %, which is well within the guideline error of 5 %. The predictive scenarios show net vertical leakage into the aquifer decreasing and net vertical leakage out of the aquifer increasing, as bore flows are reduced. These estimates of inflows and outflows complement other studies of the Basin and add to our understanding of its hydrodynamics. In this way the water balance helps provide a sound basis for the development of GAB groundwater management plans and policies. Through its water level recovery predictions, the model has also been used to support the GAB Sustainability Initiative. ¶ A transient numerical model of the GAB was also developed and tested, and predictive scenarios were run. This model builds on the steady state model, and is more complex, with a calibration period (1965-1999) that is longer than in any previous GAB model. During calibration the model observations were expressed and weighted so that the minimisation of the objective function reflected the relative importance of the model’s potential uses, these being respectively: to simulate the impact of changing bore flows, to more generally inform water management plans and to provide an estimate of the water balance. It was found that the 1960 steady state assumption was not correct. Discluding anthropogenic discharge, the model is most sensitive to recharge and hydraulic conductivity. The model-predicted heads match field measurements with a Scaled RMS error of 2.7 %, which is well within the guideline error of 5 %, but the increased data requirements of the transient model highlighted deficiencies in the data available for the modelling. In particular, the uneven spread of the groundwater measurements over both time and space, the questionable accuracy of measurements from both high temperature and pressure bores, and corroded bores, and the type of discharge measured (for example, maximum yield or flow-as-found), became evident during the calibration of the model. Insights and the value of this work indicates for the first time that at the start of 2005 outflows were estimated to exceed inflows by 266 GL/year, or 62 % of total inflows, and, assuming that inflows through the aquifer’s boundary will not be reduced due to climate change, it will be possible to recover some of the lost groundwater pressure if all stock and domestic bores are rehabilitated and new extractions are limited. In this case the modelling estimates that inflows could exceed outflows by up to 40 % of total outflows.

The process of calibrating a numerical model is examined in this thesis with an application to the flow of groundwater in the Willunga Basin in South Australia. The calibration process involves estimating unknown parameters of the numerical model so that the output obtained from the model is comparable with data that is observed in the field. Three methods for calibrating numerical models are discussed, these being the steepest descent method, the nonlinear least squares method, and a new method called the response function method. The response function method uses the functional relationship between the model's output and the unknown parameters to determine improved estimates for the unknown parameters. The functional relationships are based on analytic solutions to simplifed model problems or from previous experience. The three calibration methods are compared using a simple function involving one parameter, an idealised steady state model of groundwater flow and an idealised transient model of groundwater flow. The comparison shows that the response function method produces accurate estimates in the least amount of iterations. A numerical model of groundwater flow in the Willunga Basin in South Australia has been developed and the response function method used to estimated the unknown parameters for this model. The model of the Willunga Basin has been used to examine the sustainable yield of groundwater from the basin. The effect on groundwater levels in the basin using current and estimated extraction rates from the literature for sustainable yield has been examined. The response function method has also been used to estimate the rate of extraction to return the groundwater levels at a specific location to a desirable level. / Thesis (M.Sc.)--Department of Applied Mathematics, 2001.

At head of title: National Centre for Petroleum Geology and Geophysics. / CD-ROM contains Appendices (1-10) in PDF. / Includes copies of papers co-authored by the author. / Includes bibliographical references (leaves [471]-499 in vol. 2) / System requirements for accompanying CD-ROM: Macintosh or IBM compatible computer with Windows NT. Other requirements: Adobe Acrobat Reader. / 2 v. (various pagings) : ill. (some col.), maps, ports. ; 30 cm. + 1 CD-ROM (4 3/4 in.) / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the provenance and diagenesis of the Merrimelia Formation in South Australia and Queensland; a complex mosaic of glacial facies in which the Tirrawarra Sandstone and Merrimelia Formation exhibit an interfingering relationship, and defines the relationship further. Indicates that the Tirrawarra Sandstone should be included in the Merrimelia Formation as a "facies type" as both the Merrimelia and Tirrawarra sediments form an integrated suite of sediments. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology, 2000?

"February 2001" / Bibliography: p. 335-349. / xxix, 394 p. : ill. (some col.), maps (some col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, National Centre for Petroleum Geology and Geophysics, 2004

Regional exploration in the Barrow Sub-basin has dominantly focused on structural traps in the Top Barrow Group. A lack of recent discoveries has focused attention more towards the economic potential of the Early Cretaceous intra-Barrow Group plays. The aim of this study was to interpret the seismic sequence stratigraphy and depositional history of the intra-Barrow Group within the Barrow Sub-basin, with emphasis on the identification of stratigraphic traps and potential locations of economic seal/reservoir couplets within the study area. The study area lies south of Barrow Island, and contains the topsets, foresets and toesets of the ‘Barrow delta’, which are an amalgamation of Mesozoic sandprone fluvial, coastal deltaic and deepwater successions. The final stages of the break-up of Gondwana impacted on the structural development of the Barrow Sub-basin, when a large shelf-margin fluvial/deltaic system built out toward the north to northeast, contributing to northerly shelf margin accretion, with largescale clinoform features and associated depositional environments. The dataset comprises the Flinders 3D seismic survey 1267 km² and 35 well logs. Eleven seismic sequences are identified and a seismic sequence stratigraphic framework tied to the wells has been developed, via detailed sequence stratigraphic mapping, integrated with 3D visualisation techniques with the use of Petrel. These eleven second-order sequences are further subdivided into lowstand, transgressive and highstand systems tracts. The movement of the palaeo-shelf break, slope and base of slope can be traced throughout each sequence, displaying an overall trend of building out in a north to northeast direction. A series of palaeo- geographic maps for each sequence has been developed to illustrate the basin’s evolution. The seismic sequences identified display progradation, followed by aggradation, then downstepping, concluding with progradation and aggradation. A high-resolution sequence stratigraphic study of Seismic Sequence 1 showed that several higher-order sequences can be identified, including numerous lowstand systems wedges, along with associated channel features, which could be targeted as new plays. The sequence stratigraphic framework developed, palaeo-geographic reconstructions and all other interpretations made for this project have been integrated to assess the prospectivity of the intra-Barrow Group over the study area, resulting in the identification of a number of leads and prospectivity summaries for each of the 11 Seismic Sequences identified within the intra-Barrow Group. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313353 / Thesis (M.Sc.(Petrol.G&G))-- University of Adelaide, Australian School of Petroleum, 2008

Regional exploration in the Barrow Sub-basin has dominantly focused on structural traps in the Top Barrow Group. A lack of recent discoveries has focused attention more towards the economic potential of the Early Cretaceous intra-Barrow Group plays. The aim of this study was to interpret the seismic sequence stratigraphy and depositional history of the intra-Barrow Group within the Barrow Sub-basin, with emphasis on the identification of stratigraphic traps and potential locations of economic seal/reservoir couplets within the study area. The study area lies south of Barrow Island, and contains the topsets, foresets and toesets of the ‘Barrow delta’, which are an amalgamation of Mesozoic sandprone fluvial, coastal deltaic and deepwater successions. The final stages of the break-up of Gondwana impacted on the structural development of the Barrow Sub-basin, when a large shelf-margin fluvial/deltaic system built out toward the north to northeast, contributing to northerly shelf margin accretion, with largescale clinoform features and associated depositional environments. The dataset comprises the Flinders 3D seismic survey 1267 km² and 35 well logs. Eleven seismic sequences are identified and a seismic sequence stratigraphic framework tied to the wells has been developed, via detailed sequence stratigraphic mapping, integrated with 3D visualisation techniques with the use of Petrel. These eleven second-order sequences are further subdivided into lowstand, transgressive and highstand systems tracts. The movement of the palaeo-shelf break, slope and base of slope can be traced throughout each sequence, displaying an overall trend of building out in a north to northeast direction. A series of palaeo- geographic maps for each sequence has been developed to illustrate the basin’s evolution. The seismic sequences identified display progradation, followed by aggradation, then downstepping, concluding with progradation and aggradation. A high-resolution sequence stratigraphic study of Seismic Sequence 1 showed that several higher-order sequences can be identified, including numerous lowstand systems wedges, along with associated channel features, which could be targeted as new plays. The sequence stratigraphic framework developed, palaeo-geographic reconstructions and all other interpretations made for this project have been integrated to assess the prospectivity of the intra-Barrow Group over the study area, resulting in the identification of a number of leads and prospectivity summaries for each of the 11 Seismic Sequences identified within the intra-Barrow Group. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313353 / Thesis (M.Sc.(Petrol.G&G))-- University of Adelaide, Australian School of Petroleum, 2008