Digitalcore Pty Ltd

Canberra, Australia

Digitalcore Pty Ltd

Canberra, Australia
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Banasiak L.,University of Wollongong | Indraratna B.,University of Wollongong | Regmi G.,University of Wollongong | Golab A.,Digitalcore Pty Ltd | Lugg G.,Manildra Group
Geomechanics and Geoengineering | Year: 2013

The acidification of coastal waterways because of acid sulphate soil is an environmental, economic and social problem within Australia. A pilot-scale permeable reactive barrier (PRB), using recycled concrete aggregates as reactive material, was installed in low-lying acid sulphate soil terrain for acidic groundwater remediation. Column experiments were previously undertaken with synthetic groundwater to ascertain the dominant reactions occurring within the PRB. Results showed that armouring of the reactive material surface by precipitated Al- and Fe-bearing minerals significantly reduced its acid neutralisation capacity (ANC). The purpose of this current study was to validate this decline in ANC through characterisation of the virgin and armoured concrete aggregates, and precipitates that formed on the concrete. Samples of concrete aggregates and precipitates were analysed using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy-Energy dispersive spectroscopy (SEM-EDS) and X-ray micro-computed tomography (μCT). The conclusions drawn from these analyses are that Al-bearing (gibbsite 14.3%, boehmite 10.9%) and Fe-bearing (goethite 38.2%) mineral precipitates of diverse morphology form as a thin layer coating the aggregate surfaces. A reduction of CaO in the armoured concrete aggregates by 47% correlates with the reduction in ANC of the virgin concrete by 50% due to armouring. © 2013 Copyright Taylor and Francis Group, LLC.

Regmi G.,University of Wollongong | Indraratna B.,University of Wollongong | Nghiem L.D.,University of Wollongong | Golab A.,DigitalCore Pty Ltd. | Prasad B.G.,University of Wollongong
Journal of Environmental Engineering | Year: 2011

Acidic groundwater generated from pyrite oxidation in acid sulfate (AS) soil is a major geoenvironmental problem in Australia. This study aims to evaluate recycled concrete as a reactive material in permeable reactive barriers (PRBs) for the remediation of acidic groundwater in low-lying AS soil floodplains. Laboratory experiments were systematically conducted to investigate the acid neutralization behavior of recycled concrete and its potential to remove dissolved Al and Fe. The results confirmed that recycled concrete could effectively treat acidic groundwater from an AS soil terrain, resulting in near neutral effluent over a long period with complete removal of Al and Fe. The major mechanisms involved in neutralizing acidic groundwater are thought to be the precipitation of Al and Fe as oxides, oxyhydroxides, and hydroxides. However, the accumulation of secondary minerals could decrease the reactivity of the recycled concrete. For example, chemical armoring could decrease the neutralizing capacity of recycled concrete by up to 50% compared with the theoretical acid neutralization capacity of this material. The results reported here also show that the neutralization capacity and reactive efficiency of recycled concrete are dependent on the initial pH value and also the concentration of Al and Fe in acidic groundwater. © 2011 American Society of Civil Engineers.

Golab A.,Digitalcore Pty Ltd | Romeyn R.,Geoscience Australia | Averdunk H.,Australian National University | Knackstedt M.,Digitalcore Pty Ltd | Senden T.J.,Australian National University
Australian Journal of Earth Sciences | Year: 2013

Digital core analysis at multiple scales incorporating X-ray micro-computed tomography (μCT) imaging in different states in 3D, and registration of 2D SEM and SEM-energy-dispersive X-ray spectra (EDS) images into the 3D tomograms, offers an extensive and unique toolbox for characterising potential CO2 reservoir and seal candidates. μCT imaging allows the calculation of connected porosity, and subsequently properties such as permeability, formation factor, Archie's cementation component, drainage capillary pressure, and Swi can be determined digitally and pore-throat network models can be generated. Sub-micron scale features in the 3D image can be directly correlated with high-resolution scanning electron microscope (SEM) images using 2D-to-3D image registration. Additionally, the in situ mineralogy can be quantified by using an automated mineral and petrological analysis (SEM-EDS) system. The mineralogy determined in 2D by SEM-EDS can then be interpolated into the 3D image block for the direct identification of minerals with contrasting X-ray attenuation. The 3D data can be readily displayed using 3D visualisations that show the pore connectivity, 3D mineralogy, geological structures, and incorporating the pore-throat network model, SEM, and 2D in situ mineral map. Additionally the porosity and flow pathways of a potential seal rock can be characterised at the nanoscale (pores 10-30 nm) using focussed ion beam SEM (FIBSEM) imaging. The behaviour of the potential reservoir and seal rocks during interaction with supercritical CO2 and water can be directly investigated by coupling digital core analysis with a high-pressure cell. Multiple images can be collected of the same plug before, during and after interaction with CO2 and water to directly characterise in 3D the CO2 trapping, and changes to the pore/throat geometries and mineralogy owing to interactions with the CO2. © 2013 Copyright Taylor and Francis Group, LLC.

Fogden A.,Australian National University | Kumar M.,DigitalCore Pty Ltd | Morrow N.R.,University of Wyoming | Buckley J.S.,University of Wyoming
Energy and Fuels | Year: 2011

The mounting evidence that waterflooding of clay-containing sandstone reservoirs using floodwater with reduced salinity can enhance oil recovery, but with unpredictably large variation in responses, demands improved understanding of the underlying mechanisms. Mobilization of clays and other fines is one candidate mechanism. Flow experiments in Berea sandstone plugs were designed such that the change in their fines distribution from before to after the oil and water injections could be imaged in exactly the same pores using scanning electron microscopy. This technique also allowed imaging of the wettability distribution on pore surfaces and was coupled to spectroscopic analysis of the adsorbed asphaltene amounts. One-phase flows switching from high- to low-salinity water led to only a low level of fines mobilization, compared to two-phase experiments in which high- or low-salinity water displaced crude oil from mixed-wet prepared plugs. The images reveal that loosely bound, partially oil-wet fines lining sandstone grains are stripped by the adhering oil during its recovery and redeposited on grains further downstream. Reduced salinity increases the fraction of fines thus mobilized by weakening their bonds to grains and strengthening their bonds to oil. Evidence suggests that these more oil-wet fines stabilize the water-in-oil curved menisci, which can aid in maintaining the connectivity of the oil phase and thus enhance oil recovery. © 2011 American Chemical Society.

Kumar M.,Digitalcore Pty. Ltd. | Senden T.J.,Australian National University | Sheppard A.P.,Australian National University | Middleton J.P.,Australian National University | Knackstedt M.A.,Digitalcore Pty. Ltd.
Petrophysics | Year: 2010

At the conclusion of flooding in an oil- or gas-bearing reservoir, a significant fraction of the original hydrocarbon in place remains in the swept region as trapped residual phase. In addition to the amount of trapped phase, its microscopic distribution within the pore space of a reservoir rock is important to gain a better understanding of recovery mechanisms and for the design and implementation of tertiary recovery processes. Despite the importance of the pore scale structure and distribution of residual oil, little quantitative information is currently available. We utilize a technique for imaging the pore-scale distribution of fluids in reservoir cores. The method allows the same core to be imaged after flooding under different wettability conditions, saturation states and flooding rates. Secondary and tertiary floods can be considered. Recovery mechanisms can be directly tested and the differences in the habitat of the residual fluids under different conditions can be directly quantified. We present results for imbibition experiments on a number of sandstone and reservoir carbonate samples of varying complexity. The role of rate, wettability and initial water saturation on residual phase saturations are given. The detailed structure of the residual trapped phase is described; the size distributions of residual oil blobs, features of blob shape and dimensions are enumerated and compared under variable flooding conditions. These results provide an important platform for both the understanding of pore scale displacement mechanisms and for the testing and calibration of image and network based models of multiphase flow. © 2010 Society of Petrophysics and Well Log Analysts.

Feali M.,University of New South Wales | Pinczewski W.V.,University of New South Wales | Cinar Y.,University of New South Wales | Arns C.H.,University of New South Wales | And 5 more authors.
SPE Latin American and Caribbean Petroleum Engineering Conference Proceedings | Year: 2012

It is now widely acknowledged that continuous oil spreading films observed in two-dimensional glass micro-model studies for strongly water wet three-phase oil, water and gas systems are also present in real porous media and result in lower tertiary gas flood residual oil saturations than for corresponding negative spreading systems which do not display oil spreading behavior. However, it has not been possible to directly confirm the presence of spreading films in real porous media in threedimensions and little is understood of the distribution of the phases within the complex geometry and topology of actual porous media for different spreading conditions. This paper describes a preliminary study using high resolution X-ray microtomography to image the distribution of oil, water and gas after tertiary gas flooding to recover waterflood residual oil for two set of fluids, one positive spreading and the other negative spreading, for strongly water wet conditions in Bentheimer sandstone. We show that for strongly water-wet conditions and a positive spreading system the oil phase remains connected throughout the pore space and results in a low tertiary gas flood residual oil saturation. The residual oil saturation for the corresponding negative spreading system is significantly higher and this is shown to be related to the absence of oil films in this system. The presence of films for positive spreading systems and the absence of such films for negative spreading systems is further confirmed by the computation of the Eurler characteristic for each phase. Copyright 2012, Society of Petroleum Engineers.

Golab A.,Digitalcore Pty Ltd | Ward C.R.,University of New South Wales | Permana A.,University of New South Wales | Lennox P.,University of New South Wales | Botha P.,FEI Australia Pty Ltd
International Journal of Coal Geology | Year: 2013

Samples of coal from the Sydney and Bowen Basins of eastern Australia have been imaged at high resolution using a large-field, 3D microfocus X-ray computed tomography (μCT) system, with special but not exclusive attention to evaluating the modes of occurrence of the mineral matter within the coal. The samples imaged were 110mm, 25mm, 19mm, 10mm, and 4mm in size, yielding voxel dimensions of 54, 30, 12, 6, and 3μm respectively. Data collection was carried out using a helical stage, providing images with >20002voxels in the horizontal (X-Y) plane and up to 3500voxels high. Three-dimensional image blocks derived from the scans were examined as cross-sections along orthogonal planes and as perspective images, manipulated to be viewed from any angle. Imaging after saturating the coal with X-ray attenuating brine was also carried out to highlight the distribution of connected micro-pores and cleats, and improve the detail of features seen within the samples.Features evaluated within the coals included the size and three-dimensional distribution of siderite nodules, and different types of mineral infillings in petrifactions of maceral components. Individual macerals could also be identified within the coal, based partly on X-ray density and partly on the associated porosity and structure. In some cases high-resolution images enabled the nature of individual plant particles to be identified within the coal samples. Mineral-filled cleats and open fractures were also evaluated, including the origin of radiating fracture patterns around siderite nodules in vitrinite. In some cases several generations of cleat and/or fractures could be distinguished, and the sequence of their formation and infilling was interpreted.Complementary analyses of the mineral matter in the samples were carried out using X-ray diffraction, as well as examination of polished sections by optical microscopy examination. Images obtained from the μCT scans were also registered against SEM-EDX and QemSCAN images of polished sections prepared from the same samples after scanning, providing a more definitive basis for identifying the different components and for integrating μCT data with results from other petrographic and electron microscope studies. © 2012 Elsevier B.V.

Riepe L.,Petronas | Suhaimi M.H.B.,Petronas | Kumar M.,Digitalcore Pty. Ltd. | Knackstedt M.A.,Digitalcore Pty. Ltd.
Society of Petroleum Engineers - SPE Middle East Unconventional Gas Conference and Exhibition 2011, UGAS | Year: 2011

The paper provides a case history of the application of 3D imaging and Pore Network Modeling (PNM) technology to establish a direct relationship between rock micro-structure parameters from 3D via micro-tomographic images, and the simulation of petrophysical properties of clastic tight gas reservoir rocks in Oman. Tight gas reservoirs exhibit storage and flow characteristics that are intimately tied to the depositional and diagenetic processes. In particular, cores have significant primary and secondary porosity often dominated by clays and slot like pores. Accurately mapping the pore and grain structure and mineralogy in 3D and the interconnectivity of primary and secondary porosity illustrates the role 3D imaging plays in a comprehensive reservoir characterization program. The computed petrophysical properties (e.g. porosity, permeability, formation resistivity factor, hydraulic radii and drainage capillary pressure) are compared with routine and special core analysis results measured on conventional core samples. The use of 3D micro-tomograms at different scales and PNM provides a quick complimentary method to characterize the distribution and nature of different pore types and matrix components to characterize the static, elastic and dynamic rock properties even on rock fragments (2mm to 1cm diameter) that are not suitable for conventional core analysis techniques. The presented case history demonstrates that the new 3D PNM technologies can also be successfully applied to the challenging tight gas reservoirs with low porosities and very low permeabilities for comprehensive reservoir characterization to optimize the development scenarios. Copyright 2011, Society of Petroleum Engineers.

Kumar M.,Digitalcore Pty. Ltd. | Senden T.J.,Australian National University | Sheppard A.P.,Australian National University | Arns C.H.,University of New South Wales | Knackstedt M.A.,Digitalcore Pty. Ltd.
Petrophysics | Year: 2011

The saturation exponent, n, is often assumed to be two in the absence of core data, but a variety of " values have been reported. This uncertainty in n may be due to pore geometrical and topological complexities, structural heterogeneities coupled with variations in wettability. As values of " are correlated to oil-in-place, good estimates of n are needed. Recently, an X-ray μ-CT imaging registration technique was developed where multiphase fluid saturations can be measured in-situ on a pore scale basis within reservoir miniplugs. Using this technique, one can obtain information on the relative fluid affinity for specific pore regions, as well as the connate wetting phase saturations and habitat of the hydrocarbon and wetting fluid within the rock at the pore scale. From the observed fluid saturations one may use numerical simulations to predict the value of n and better understand reasons for deviations in the saturation exponent from the conventional values. In this paper, we describe analyses undertaken on both clastic and carbonate samples under variable saturation conditions. Coupling 3D imaging, high-resolution SEM analysis, and in-situ observations of fluid saturation enables one to understand the observed resistivity response of various samples under different saturation conditions. In a first set of experiments, we discuss the observed behavior on a clean water-wet sandstone; in experiments, one observes n ≈ 2 at high to intermediate water saturations (Sw), but at lower Sw, " < 2. Using a combination of μ-CT, image registration and cryo-SEM analysis we observe that at low Sw water films in those clean sands concentrate at or on the perimeter of grain contacts. 3D analysis shows the grain contacts span the rock structure. Simulation results show that the inclusion of a realistic thin water film within grain contacts results in a match to the measured behavior for RI. Analyses are also performed on carbonates under variable wettability conditions. The role of microporosity, wettability, and saturation history on pore scale fluid distributions and thus resistivity response is discussed. The results underline the potential importance of microporosity in determining saturation exponents at low Sw. Capturing porosity information at all scales gives better estimation of original oil-in-place, particularly for carbonates displaying a wide variety of pore structure and wettability behaviors. © 2011 Society of Petrophysics and Well Log Analysts. All Rights Reserved.

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