Jim Buckman | Heriot-Watt University (original) (raw)
Papers by Jim Buckman
Acta Geotechnica, 2013
Environmental scanning electron microscopy (ESEM) and nanoindentation investigation of the crack ... more Environmental scanning electron microscopy (ESEM) and nanoindentation investigation of the crack tip process zone in marble The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.
Bulletin of the Geological Society of Greece
During a whole year (March 2003 to February 2004), several filters that capture airborne particle... more During a whole year (March 2003 to February 2004), several filters that capture airborne particles were collected from seven sampling sites spread throughout the Ptolemais-Kozani region (Western Macedonia), northern Greece. Environmental Scanning Electron Microscopy (ESEM), coupled with Energy Dispersive X-Ray analysis (EDX) was employed for the characterisation of the airborne particles. A classification of these airborne particles is attempted in this study. Aerosols with various morphological characteristics (angular, irregular, rounded, spherical, spheroidal, acicular), variable size (mostly between 5ßm and 20pm) and composition (aluminosilicates, oxides, carbonates, sulphates, metallic) were recognized. The airborne particulates were also categorized according to their origin. Geogenie, biogenic, anthropogenic (mainly fly ash released from lignite-fired power plants), carbonaceous and metalliferous (mainly iron and copper enriched) were the main categories. A database of charac...
Blue-Green Systems, 2022
Ponds and the adjacent green spaces are an important part of urban blue-green Infrastructure (BGI... more Ponds and the adjacent green spaces are an important part of urban blue-green Infrastructure (BGI) and contribute to a number of ecosystem services, including alleviation of flood risk, amelioration of climatic fluctuations, and improvement of runoff water quality, as well as biodiversity and amenity values. Multiple benefits associated with urban ponds have only recently started to be appreciated, and examples of in-depth interdisciplinary insights remain rare. This paper gives an account of the ecosystem services provided by Blackford Pond, a semi-natural water body located within a nature reserve and nominated as a site globally important for scientific research. Despite elevated levels of polluting substances and eutrophication, the overall species richness of the site is high and the biodiversity of the locality is enhanced by the ecotone effect. The diversity of available plant hosts and substrates appears to benefit the fungal community and the abundance of aquatic invertebra...
Automated scanning electron microscopy image collection from geological polished thin sections, i... more Automated scanning electron microscopy image collection from geological polished thin sections, in conjunction with autonomous stitching, can be used to construct high-resolution (micronto submicron-resolution) image montages over areas up to several square centimeters. The technique is here applied to an oolitic limestone and a carbonate laminite to illustrate its application as a tool to study carbonate porosity and diagenesis. Montages constructed from backscattered images are ideally suited to the extraction of data on microporosity, with possibilities including the construction of contoured maps to illustrate the spatial variation in porosity; the construction of porosity logs to illustrate trends in porosity across thin sections; and stochastic construction of digital rock models, for subsequent permeability calculation. Montages taken with a gaseous secondary electron detector in low-vacuum mode can utilize charge contrast imaging (CCI) at a variety of scales and were used he...
Minerals, 2021
Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly du... more Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is ...
Energies, 2021
Geological storage of CO2 in saline aquifers and depleted oil and gas reservoirs can help mitigat... more Geological storage of CO2 in saline aquifers and depleted oil and gas reservoirs can help mitigate CO2 emissions. However, CO2 leakage over a long storage period represents a potential concern. Therefore, it is critical to establish a good understanding of the interactions between CO2–brine and cement–caprock/reservoir rock to ascertain the potential for CO2 leakage. Accordingly, in this work, we prepared a unique set of composite samples to resemble the cement–reservoir rock interface. A series of experiments simulating deep wellbore environments were performed to investigate changes in chemical, physical, mechanical, and petrophysical properties of the composite samples. Here, we present the characterisation of composite core samples, including porosity, permeability, and mechanical properties, determined before and after long-term exposure to CO2-rich brine. Some of the composite samples were further analysed by X-ray microcomputed tomography (X-ray µ-CT), X-ray diffraction (XRD)...
WIT Transactions on The Built Environment, 2020
Stormwater retention ponds are an important part of blue-green infrastructure, providing multiple... more Stormwater retention ponds are an important part of blue-green infrastructure, providing multiple benefits associated with flood resilience, water quality improvements, wildlife habitat creation and increases in amenity and biodiversity values. Here we compare two ponds in Edinburgh (Scotland): Oxgangs and Juniper Green. These were both established 10-15 years ago during construction of housing estates and are 3.5 km apart. The volumes of the ponds were calculated using detailed hydrographic data (obtained as part of this study). Delineation of catchments was performed using fine resolution DEM data together with details of the storm water sewer network. Hydrological and hydrodynamic modelling was carried out using the SHETRAN and CityCAT models. The presence of the ponds not only delays peak discharge after an extreme precipitation event but also reduces it rather considerably. Reductions in peak discharge and delay are much bigger for the larger Oxgangs pond, giving a 45% reduction in discharge and a 5-minute delay for a 15-minute one-in-100-year event. Data obtained on water chemistry, abundance of planktonic organisms and abundance of macroinvertebrates suggest that the increase in pollutant levels affects biological water quality and the ecosystem structure. Oxgangs pond has much higher electrical conductivity, corresponding to higher concentrations of specific elements and lower macroinvertebrate indices than Juniper Green. However, the water in Juniper Green is enriched in Ag, Pb and a number of REE, which may be related to discarded electronics. In addition to the flood resilience and water quality benefits, both ponds provide considerable amenity and biodiversity value. To date, there are 103 and 22 species of vascular plants, 20 and 16 species of bryophytes, 5 and 2 species of non-lichenised fungi and 11 and 4 species of epiphytic lichens recorded, respectively, at Oxgangs and Juniper Green. The results presented here have implications for further research and stormwater pond design and management practices.
Palaeontologia Electronica, 2020
Exceptionally well-preserved examples of the calcareous annelid tube Ditrupa bartonensis occur wi... more Exceptionally well-preserved examples of the calcareous annelid tube Ditrupa bartonensis occur within clays of the Eocene Barton Beds Formation of Hampshire, UK, where it is the most common of four recorded annelid species (D. bartonensis, Protula extensa, Pyrgopolon (Serpula) crassa, Pyrgopolon (Sclerostyla) mellevillei). The current work confirms that i) chevron-shaped lamellae are present within Ditrupa, and that ii) all microstructures in Ditrupa are conservative (Eocene to present)-including the inner tube structure, which has only been previously recorded from extant material. New observations of the regularly ridged prismatic (RRP) structure of the outer layer illustrate the occurrence of conchoidal fractures, which are likely to represent the influence of acidic proteins within their calcite crystalline structure. The occurrence of conchoidal fractures, and the intricate non-crystalline external appearance of RRP structure, suggests a similar mode of formation to that of the single calcite crystals that form the plates and spines within echinoderms, and likely reflect an adaptation for tube strengthening, as previously postulated. A tentative model for RRP construction based on the formation of echinoderm single calcite crystals is suggested with the aim of stimulating further research. The inner layer, which comprises partially aligned slender prismatic crystals, was previously referred to as irregularly orientated prismatic (IOP) fabric, but does not fit the original description. Therefore, simple preferentially orientated prismatic (SPOP) is introduced for such fabric that forms the inner layer of Ditrupa.
Journal of Electronic Materials, 2017
Thermoelectric technology has not yet been able to reach full-scale market penetration partly bec... more Thermoelectric technology has not yet been able to reach full-scale market penetration partly because most commercial materials employed are scarce/costly, environmentally unfriendly, in addition to providing low conversion efficiency. The necessity to tackle some of these hurdles leads us to investigate the suitability of ntype hydrogenated microcrystalline silicon (µc-Si: H) in the fabrication of thermoelectric devices, produced by plasma enhanced chemical vapour deposition (PECVD), which is a mature process of proven scalability. This study reports an approach to optimise the thermoelectric power factor (PF) by varying the dopant concentration by means of post-annealing without impacting film morphology, at least for temperatures below 550°C. Results show an improvement in PF of more than 80% , which is driven by a noticeable increase of carrier mobility and Seebeck coefficient in spite of a reduction in carrier concentration. A PF of 2.08 x 10-4 W/mK 2 at room temperature is reported for n-type films of 1µm thickness, which is in line with the best values reported in recent literature for similar structures.
Journal of Sedimentary Research, 2016
Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique tha... more Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique that can be induced through partial surface charge suppression of uncoated nonconductive samples, imaged with a suitable detector such as a gaseous secondary electron detector (GSED). The technique commonly produces results similar in style to that of SEM-cathodoluminescence (SEM-CL), providing information on zoning, twinning, annealed fractures, and subtle chemical changes. The current work outlines an example from a Brazilian Lower Cretaceous coquina limestone, in which both optical and SEM-CL imaging produces a limited response from much of the sample. Backscattered electron (BSE) imaging typically suggests only a hint of the cement present, whereas CCI clearly displays a rich and varied cement stratigraphy. The earliest cement displays strong CCI, but appears mainly dark under CL imaging conditions (SEM-CL and optical CL). Later-stage manganese-"enriched" carbonate cement displays luminescence with both optical and SEM-CL, as well as a CCI response. Therefore CCI can provide additional information on cement zonation in an area where CL cannot.
Materials Characterization, 2018
Dual testing methodology for in-situ monitoring of early hydration presented • Automated image co... more Dual testing methodology for in-situ monitoring of early hydration presented • Automated image collection applied to the WetSEM technology for the first time • WetSEM images correlate with data from electrical impedance measurements • Portlandite precipitation alters both conduction and polarization processes • Double-layer and interfacial processes give rise to the bulk polarization
Geosciences, 2019
Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid pa... more Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid particulates (grains) and pores, which have a given pore network architecture relationship, and associated porosity—permeability values. Over time, through the process of diagenesis, the pore network architecture may be extensively altered. Changes can include compaction, particle deformation, cementation, dissolution and fracturing, with the pathway followed after deposition depending on factors such as the energy level, rate of burial, degree of biological activity, local heat flow, sediment composition, Eh, pH and the presence or absence of organic materials. Any method that provides a means of modelling changes is therefore highly desirable, in particular, allowing a prediction of changes in porosity and permeability with time. The current work illustrates a simple method that uses freely available open source image analysis software to model the development of cement phases within an ...
Journal of Electronic Materials, 2019
Most approaches to silicon-based thermoelectrics are focused on reducing the lattice thermal cond... more Most approaches to silicon-based thermoelectrics are focused on reducing the lattice thermal conductivity with minimal deterioration of the thermoelectric power factor. This study investigates the potential of p-type hydrogenated nano-crystalline silicon thin films (µc-Si: H), produced by plasma enhanced chemical vapour deposition, for thermoelectric applications. We adopt this heterogeneous material structure, known to have a very low thermal conductivity (~ 1 W/m K), in order to obtain an optimized power factor through controlled variation of carrier concentration drawing on stepwise annealing. This approach achieves a best thermoelectric power factor of ~3 x 10-4 W/mK 2 at a carrier concentration of ~ 4.5 x 10 19 cm 3 derived from a significant increase of electrical conductivity ~ x 8, alongside a less pronounced reduction of Seebeck coefficient, while retaining a low thermal conductivity. These thin films have a good thermal and mechanical stability up to 500°C with appropriate adhesion at the film/substrate interface.
Earth Science Research, 2017
Quartz cement forming as syntaxial overgrowths is one of the most abundant cement type in sandsto... more Quartz cement forming as syntaxial overgrowths is one of the most abundant cement type in sandstones. The rim and occluding cements develop around the surfaces of frame work grains and fill up pore spaces with no preferred orientation with grain surfaces. Imaging the various forms of quartz cement generation and development in 3D as it increases through time will help in further evaluation and better understanding of a reservoir in deep water sands in Niger Delta Basin.Petrographic analysis was performed on 10 Samples with micron resolutions of 0.675 and 0.337 per pixel. Scanning Electron Microscopy (SEM) using the Cathoduluminiscence (CL) and Back Scattered Electron (BSE) was employed in delineating the detrital quartz from the syntaxial quartz cements. Image J Software and Scandium Software were employed in binarizing the BSE image samples and study the iteration porosity, final porosity and permeability. 3DSlicer software was employed to produce 3D images for better understanding...
Geological Society, London, Special Publications, 2016
Petroleum exploration and production in the region of the Niger Delta to date has mainly focused ... more Petroleum exploration and production in the region of the Niger Delta to date has mainly focused on the onshore, deltaic and offshore deep-water Miocene successions. Although Miocene turbidites have been the principal deep-water target, deeper-lying Oligocene sandstones are now being considered for exploration. This study targets an area beneath the Niger Basin slope at a present-day water depth of 800–1500 m. Within this study area, the Miocene to Recent sands above a burial depth of 3600 m show very good reservoir quality with porosities as high as 35% and permeabilities in the Darcy range. The aim of this study is to predict the reservoir quality and properties of the Oligocene sandstones below 3800 m using basin modelling to predict conditions where quartz cementation will take place and quartz cementation models to predict the amount of cementation and hence the potential porosity loss. Modelling results show that the Oligocene sandstones have been exposed to conditions favoura...
Energy Procedia, 2017
In a CO2 storage site, carbonate rocks might be good reservoir rocks or good seals depending on t... more In a CO2 storage site, carbonate rocks might be good reservoir rocks or good seals depending on their porosity and permeability. However, these properties may change in time due to deformation processes related to CO2 injections and/or withdraws. In this pilot study, we investigate at the laboratory scale the influence of CO2-induced geochemical reactions on the mechanical integrity of carbonate rocks. To achieve this target, we have performed an experimental HP-HT test on brine saturated oolitic limestone samples that were exposed to 230 bar CO2 pressure and 37.5 o C reaction temperature (supercritical conditions) for a period of 2 weeks. Although changes in fluid chemistry have been identified via ICP-OES analysis, we have observed no particular differences in terms of ooids and cement deformation and/or calcite dissolution when comparing ESEM images of pre-and posttreatment samples. We are currently performing more experiments under different conditions (particularly longer exposure and higher brine-rock ratios that can be linked to higher dissolution of calcite) in order to better understand the dominant CO2 sequestration mechanisms in oolitic limestone-containing reservoirs.
Acta Geotechnica, 2013
Environmental scanning electron microscopy (ESEM) and nanoindentation investigation of the crack ... more Environmental scanning electron microscopy (ESEM) and nanoindentation investigation of the crack tip process zone in marble The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.
Bulletin of the Geological Society of Greece
During a whole year (March 2003 to February 2004), several filters that capture airborne particle... more During a whole year (March 2003 to February 2004), several filters that capture airborne particles were collected from seven sampling sites spread throughout the Ptolemais-Kozani region (Western Macedonia), northern Greece. Environmental Scanning Electron Microscopy (ESEM), coupled with Energy Dispersive X-Ray analysis (EDX) was employed for the characterisation of the airborne particles. A classification of these airborne particles is attempted in this study. Aerosols with various morphological characteristics (angular, irregular, rounded, spherical, spheroidal, acicular), variable size (mostly between 5ßm and 20pm) and composition (aluminosilicates, oxides, carbonates, sulphates, metallic) were recognized. The airborne particulates were also categorized according to their origin. Geogenie, biogenic, anthropogenic (mainly fly ash released from lignite-fired power plants), carbonaceous and metalliferous (mainly iron and copper enriched) were the main categories. A database of charac...
Blue-Green Systems, 2022
Ponds and the adjacent green spaces are an important part of urban blue-green Infrastructure (BGI... more Ponds and the adjacent green spaces are an important part of urban blue-green Infrastructure (BGI) and contribute to a number of ecosystem services, including alleviation of flood risk, amelioration of climatic fluctuations, and improvement of runoff water quality, as well as biodiversity and amenity values. Multiple benefits associated with urban ponds have only recently started to be appreciated, and examples of in-depth interdisciplinary insights remain rare. This paper gives an account of the ecosystem services provided by Blackford Pond, a semi-natural water body located within a nature reserve and nominated as a site globally important for scientific research. Despite elevated levels of polluting substances and eutrophication, the overall species richness of the site is high and the biodiversity of the locality is enhanced by the ecotone effect. The diversity of available plant hosts and substrates appears to benefit the fungal community and the abundance of aquatic invertebra...
Automated scanning electron microscopy image collection from geological polished thin sections, i... more Automated scanning electron microscopy image collection from geological polished thin sections, in conjunction with autonomous stitching, can be used to construct high-resolution (micronto submicron-resolution) image montages over areas up to several square centimeters. The technique is here applied to an oolitic limestone and a carbonate laminite to illustrate its application as a tool to study carbonate porosity and diagenesis. Montages constructed from backscattered images are ideally suited to the extraction of data on microporosity, with possibilities including the construction of contoured maps to illustrate the spatial variation in porosity; the construction of porosity logs to illustrate trends in porosity across thin sections; and stochastic construction of digital rock models, for subsequent permeability calculation. Montages taken with a gaseous secondary electron detector in low-vacuum mode can utilize charge contrast imaging (CCI) at a variety of scales and were used he...
Minerals, 2021
Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly du... more Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is ...
Energies, 2021
Geological storage of CO2 in saline aquifers and depleted oil and gas reservoirs can help mitigat... more Geological storage of CO2 in saline aquifers and depleted oil and gas reservoirs can help mitigate CO2 emissions. However, CO2 leakage over a long storage period represents a potential concern. Therefore, it is critical to establish a good understanding of the interactions between CO2–brine and cement–caprock/reservoir rock to ascertain the potential for CO2 leakage. Accordingly, in this work, we prepared a unique set of composite samples to resemble the cement–reservoir rock interface. A series of experiments simulating deep wellbore environments were performed to investigate changes in chemical, physical, mechanical, and petrophysical properties of the composite samples. Here, we present the characterisation of composite core samples, including porosity, permeability, and mechanical properties, determined before and after long-term exposure to CO2-rich brine. Some of the composite samples were further analysed by X-ray microcomputed tomography (X-ray µ-CT), X-ray diffraction (XRD)...
WIT Transactions on The Built Environment, 2020
Stormwater retention ponds are an important part of blue-green infrastructure, providing multiple... more Stormwater retention ponds are an important part of blue-green infrastructure, providing multiple benefits associated with flood resilience, water quality improvements, wildlife habitat creation and increases in amenity and biodiversity values. Here we compare two ponds in Edinburgh (Scotland): Oxgangs and Juniper Green. These were both established 10-15 years ago during construction of housing estates and are 3.5 km apart. The volumes of the ponds were calculated using detailed hydrographic data (obtained as part of this study). Delineation of catchments was performed using fine resolution DEM data together with details of the storm water sewer network. Hydrological and hydrodynamic modelling was carried out using the SHETRAN and CityCAT models. The presence of the ponds not only delays peak discharge after an extreme precipitation event but also reduces it rather considerably. Reductions in peak discharge and delay are much bigger for the larger Oxgangs pond, giving a 45% reduction in discharge and a 5-minute delay for a 15-minute one-in-100-year event. Data obtained on water chemistry, abundance of planktonic organisms and abundance of macroinvertebrates suggest that the increase in pollutant levels affects biological water quality and the ecosystem structure. Oxgangs pond has much higher electrical conductivity, corresponding to higher concentrations of specific elements and lower macroinvertebrate indices than Juniper Green. However, the water in Juniper Green is enriched in Ag, Pb and a number of REE, which may be related to discarded electronics. In addition to the flood resilience and water quality benefits, both ponds provide considerable amenity and biodiversity value. To date, there are 103 and 22 species of vascular plants, 20 and 16 species of bryophytes, 5 and 2 species of non-lichenised fungi and 11 and 4 species of epiphytic lichens recorded, respectively, at Oxgangs and Juniper Green. The results presented here have implications for further research and stormwater pond design and management practices.
Palaeontologia Electronica, 2020
Exceptionally well-preserved examples of the calcareous annelid tube Ditrupa bartonensis occur wi... more Exceptionally well-preserved examples of the calcareous annelid tube Ditrupa bartonensis occur within clays of the Eocene Barton Beds Formation of Hampshire, UK, where it is the most common of four recorded annelid species (D. bartonensis, Protula extensa, Pyrgopolon (Serpula) crassa, Pyrgopolon (Sclerostyla) mellevillei). The current work confirms that i) chevron-shaped lamellae are present within Ditrupa, and that ii) all microstructures in Ditrupa are conservative (Eocene to present)-including the inner tube structure, which has only been previously recorded from extant material. New observations of the regularly ridged prismatic (RRP) structure of the outer layer illustrate the occurrence of conchoidal fractures, which are likely to represent the influence of acidic proteins within their calcite crystalline structure. The occurrence of conchoidal fractures, and the intricate non-crystalline external appearance of RRP structure, suggests a similar mode of formation to that of the single calcite crystals that form the plates and spines within echinoderms, and likely reflect an adaptation for tube strengthening, as previously postulated. A tentative model for RRP construction based on the formation of echinoderm single calcite crystals is suggested with the aim of stimulating further research. The inner layer, which comprises partially aligned slender prismatic crystals, was previously referred to as irregularly orientated prismatic (IOP) fabric, but does not fit the original description. Therefore, simple preferentially orientated prismatic (SPOP) is introduced for such fabric that forms the inner layer of Ditrupa.
Journal of Electronic Materials, 2017
Thermoelectric technology has not yet been able to reach full-scale market penetration partly bec... more Thermoelectric technology has not yet been able to reach full-scale market penetration partly because most commercial materials employed are scarce/costly, environmentally unfriendly, in addition to providing low conversion efficiency. The necessity to tackle some of these hurdles leads us to investigate the suitability of ntype hydrogenated microcrystalline silicon (µc-Si: H) in the fabrication of thermoelectric devices, produced by plasma enhanced chemical vapour deposition (PECVD), which is a mature process of proven scalability. This study reports an approach to optimise the thermoelectric power factor (PF) by varying the dopant concentration by means of post-annealing without impacting film morphology, at least for temperatures below 550°C. Results show an improvement in PF of more than 80% , which is driven by a noticeable increase of carrier mobility and Seebeck coefficient in spite of a reduction in carrier concentration. A PF of 2.08 x 10-4 W/mK 2 at room temperature is reported for n-type films of 1µm thickness, which is in line with the best values reported in recent literature for similar structures.
Journal of Sedimentary Research, 2016
Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique tha... more Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique that can be induced through partial surface charge suppression of uncoated nonconductive samples, imaged with a suitable detector such as a gaseous secondary electron detector (GSED). The technique commonly produces results similar in style to that of SEM-cathodoluminescence (SEM-CL), providing information on zoning, twinning, annealed fractures, and subtle chemical changes. The current work outlines an example from a Brazilian Lower Cretaceous coquina limestone, in which both optical and SEM-CL imaging produces a limited response from much of the sample. Backscattered electron (BSE) imaging typically suggests only a hint of the cement present, whereas CCI clearly displays a rich and varied cement stratigraphy. The earliest cement displays strong CCI, but appears mainly dark under CL imaging conditions (SEM-CL and optical CL). Later-stage manganese-"enriched" carbonate cement displays luminescence with both optical and SEM-CL, as well as a CCI response. Therefore CCI can provide additional information on cement zonation in an area where CL cannot.
Materials Characterization, 2018
Dual testing methodology for in-situ monitoring of early hydration presented • Automated image co... more Dual testing methodology for in-situ monitoring of early hydration presented • Automated image collection applied to the WetSEM technology for the first time • WetSEM images correlate with data from electrical impedance measurements • Portlandite precipitation alters both conduction and polarization processes • Double-layer and interfacial processes give rise to the bulk polarization
Geosciences, 2019
Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid pa... more Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid particulates (grains) and pores, which have a given pore network architecture relationship, and associated porosity—permeability values. Over time, through the process of diagenesis, the pore network architecture may be extensively altered. Changes can include compaction, particle deformation, cementation, dissolution and fracturing, with the pathway followed after deposition depending on factors such as the energy level, rate of burial, degree of biological activity, local heat flow, sediment composition, Eh, pH and the presence or absence of organic materials. Any method that provides a means of modelling changes is therefore highly desirable, in particular, allowing a prediction of changes in porosity and permeability with time. The current work illustrates a simple method that uses freely available open source image analysis software to model the development of cement phases within an ...
Journal of Electronic Materials, 2019
Most approaches to silicon-based thermoelectrics are focused on reducing the lattice thermal cond... more Most approaches to silicon-based thermoelectrics are focused on reducing the lattice thermal conductivity with minimal deterioration of the thermoelectric power factor. This study investigates the potential of p-type hydrogenated nano-crystalline silicon thin films (µc-Si: H), produced by plasma enhanced chemical vapour deposition, for thermoelectric applications. We adopt this heterogeneous material structure, known to have a very low thermal conductivity (~ 1 W/m K), in order to obtain an optimized power factor through controlled variation of carrier concentration drawing on stepwise annealing. This approach achieves a best thermoelectric power factor of ~3 x 10-4 W/mK 2 at a carrier concentration of ~ 4.5 x 10 19 cm 3 derived from a significant increase of electrical conductivity ~ x 8, alongside a less pronounced reduction of Seebeck coefficient, while retaining a low thermal conductivity. These thin films have a good thermal and mechanical stability up to 500°C with appropriate adhesion at the film/substrate interface.
Earth Science Research, 2017
Quartz cement forming as syntaxial overgrowths is one of the most abundant cement type in sandsto... more Quartz cement forming as syntaxial overgrowths is one of the most abundant cement type in sandstones. The rim and occluding cements develop around the surfaces of frame work grains and fill up pore spaces with no preferred orientation with grain surfaces. Imaging the various forms of quartz cement generation and development in 3D as it increases through time will help in further evaluation and better understanding of a reservoir in deep water sands in Niger Delta Basin.Petrographic analysis was performed on 10 Samples with micron resolutions of 0.675 and 0.337 per pixel. Scanning Electron Microscopy (SEM) using the Cathoduluminiscence (CL) and Back Scattered Electron (BSE) was employed in delineating the detrital quartz from the syntaxial quartz cements. Image J Software and Scandium Software were employed in binarizing the BSE image samples and study the iteration porosity, final porosity and permeability. 3DSlicer software was employed to produce 3D images for better understanding...
Geological Society, London, Special Publications, 2016
Petroleum exploration and production in the region of the Niger Delta to date has mainly focused ... more Petroleum exploration and production in the region of the Niger Delta to date has mainly focused on the onshore, deltaic and offshore deep-water Miocene successions. Although Miocene turbidites have been the principal deep-water target, deeper-lying Oligocene sandstones are now being considered for exploration. This study targets an area beneath the Niger Basin slope at a present-day water depth of 800–1500 m. Within this study area, the Miocene to Recent sands above a burial depth of 3600 m show very good reservoir quality with porosities as high as 35% and permeabilities in the Darcy range. The aim of this study is to predict the reservoir quality and properties of the Oligocene sandstones below 3800 m using basin modelling to predict conditions where quartz cementation will take place and quartz cementation models to predict the amount of cementation and hence the potential porosity loss. Modelling results show that the Oligocene sandstones have been exposed to conditions favoura...
Energy Procedia, 2017
In a CO2 storage site, carbonate rocks might be good reservoir rocks or good seals depending on t... more In a CO2 storage site, carbonate rocks might be good reservoir rocks or good seals depending on their porosity and permeability. However, these properties may change in time due to deformation processes related to CO2 injections and/or withdraws. In this pilot study, we investigate at the laboratory scale the influence of CO2-induced geochemical reactions on the mechanical integrity of carbonate rocks. To achieve this target, we have performed an experimental HP-HT test on brine saturated oolitic limestone samples that were exposed to 230 bar CO2 pressure and 37.5 o C reaction temperature (supercritical conditions) for a period of 2 weeks. Although changes in fluid chemistry have been identified via ICP-OES analysis, we have observed no particular differences in terms of ooids and cement deformation and/or calcite dissolution when comparing ESEM images of pre-and posttreatment samples. We are currently performing more experiments under different conditions (particularly longer exposure and higher brine-rock ratios that can be linked to higher dissolution of calcite) in order to better understand the dominant CO2 sequestration mechanisms in oolitic limestone-containing reservoirs.