Cabonate-hosted hydrocarbon reservoirs will play an increasingly important role in the energy supply, as 60% of the world's remaining hydrocarbon resources are trapped within carbonate rocks. The properties of carbonates are controlled by deposition and diagenesis, which includes calcite cementation that begins immediately after deposition and may have a strong impact on subsequent diagenetic pathways. This thesis aims to understand the impact of early calcite cementation on reservoir properties through object-based modelling and Lattice Boltzmann ow simulation to obtain permeability. A Bayesian inference framework is also developed to quantify the ability of Lattice Boltzmann method to predict the permeability of porous media. Modelling focuses on the impact of carbonate grain type on properties of early cemented grainstones and on the examination of the theoretical changes to the morphology of the pore space. For that purpose process-based models of early cementation are developed in both 2D (Calcite2D) and 3D (Calcite3D, which also includes modelling of deposition). Both models assume the existence of two grain types: polycrystalline and monocrystalline, and two early calcite cement types specific to these grain types: isopachous and syntaxial, respectively. Of the many possible crystal forms that syntaxial cement can take, this thesis focuses on two common rhombohedral forms: a blocky form 01¯12 and an elongated form 40¯41. The results of the 2D and 3D modelling demonstrate the effect of competition of growing grains for the available pore space: the more monocrystalline grains present in the sample, the stronger this competition becomes and the lesser the impact of each individual grain on the resulting early calcite cement volume and porosity. The synthetic samples with syntaxial cements grown of the more elongated crystal form 40¯41 have lower porosity for the same monocrystalline grains content than synthetic samples grown following more blocky crystal form 01¯12. Moreover, permeability at a constant porosity is reduced for synthetic samples with the form 40¯41. Additionally, synthetic samples with form 40¯41 exhibit greater variability in the results as this rhombohedral form is more elongated and has the potential for producing a greater volume of cement. The results of the 2D study suggest that for samples at constant porosity the higher the proportion of monocrystalline grains are in the sample, the higher the permeability. The 3D study suggests that for samples with crystal form 01¯12 at constant porosity the permeability becomes lower as the proportion of monocrystalline grains increase, but this impact is relatively minor. In the case of samples with crystal form 40¯41 the results are inconclusive. This dependence of permeability on monocrystalline grains is weaker than in the 2D study, which is most probably a result of the bias of flow simulation in the 2D as well as of the treatment of the porous medium before the cement growth model is applied. The range of the permeability results in the 2D modelling may be artificially overly wide, which could lead to the dependence of permeability on sediment type being exaggerated. Poroperm results of the 2D modelling (10-8000mD) are in reasonable agreement with the data reported for grainstones in literature (0.1-5000mD) as well as for the plug data of the samples used in modelling (porosity 22 - 27%, permeability 200 - 3000mD), however permeability results at any given porosity have a wide range due to the bias inherent to the 2D flow modelling. Poroperm results in the 3D modelling (10 - 30, 000mD) exhibit permeabilities above the range of that reported in the literature or the plug data, but the reason for that is that the initial synthetic sediment deposit has very high permeability (58, 900mD). However, the trend in poroperm closely resembles those reported in carbonate rocks. As the modelling depends heavily on the use of Lattice Boltzmann method (flow simulation to obtain permeability results), a Bayesian inference framework is presented to quantify the predictive power of Lattice Boltzmann models. This calibration methodology is presented on the example of Fontainebleau sandstone. The framework enables a systematic parameter estimation of Lattice Boltzmann model parameters (in the scope of this work, the relaxation parameter τ ), for the currently used calibrations of Lattice Boltzmann based on Hagen-Poiseuille law. Our prediction of permeability using the Hagen-Poiseuille calibration suggests that this method for calibration is not optimal and in fact leads to substantial discrepancies with experimental measurements, especially for highly porous complex media such as carbonates. We proceed to recalibrate the Lattice Boltzmann model using permeability data from porous media, which results in a substantially different value of the optimal τ parameter than those used previously (0.654 here compared to 0.9). We augment our model introducing porosity-dependence, where we find that the optimal value for τ decreases for samples of higher porosity. In this new semi-empirical model one first identifies the porosity of the given medium, and on that basis chooses an appropriate Lattice Boltzmann relaxation parameter. These two approaches result in permeability predictions much closer to the experimental permeability data, with the porosity-dependent case being the better of the two. Validation of this calibration method with independent samples of the same rock type yields permeability predictions that fall close to the experimental data, and again the porosity-dependent model provides better results. We thus conclude that our calibration model is a powerful tool for accurate prediction of complex porous media permeability.

Abstract Nickel-titanium shape memory metal Nitinol (NiTi) is a new kind of implant material, which provides a possibility to prepare functional implants activated at body temperature and withstands kinking better than conventional metals. Applications utilizing these unique properties are a target of active research interest. Host reactions to NiTi and to the forces created by functional implants should also be studied. A functional NiTi intramedullary nail, which causes a bending force on the bone, was developed for correcting bone deformities. In the present studies, the action of the device was inverted to induce a bone deformity instead of correcting one, in order to test the hypothesis that bone modelling can be controlled using such functional nail. Implanting the nail into the medullary cavity of rat femur for twelve weeks caused bowing of the bone, retardation of its longitudinal growth, and thickening of the bone and the cortex. In another study the effects of functional and straight nails were compared. Bowing of the bone and significant overall thickening of the bone and the cortex were associated only with the functional nail, while the straight nail induced only minor thickening of the bone. Retardation of longitudinal growth was seen in both groups, and this may have been caused by perforating the distal epiphyseal plate during the nailing. Finite element model of the bone-nail combination was also created. Porous NiTi was studied as a bone graft substitute by filling a bone defect in the distal femoral metaphysis of a rat bone with porous NiTi implants of different porosities. After 30 weeks, porosity of 66.1% (mean pore size (MPS) 259μm) showed the best bone-implant contact (51%). However, porosity of 46.6% (MPS 505μm) with 39% bone-implant contact was not significantly inferior in this respect and showed a significantly lower incidence of fibrosis within the implant and thus seemed to be the best choice for a bone graft substitute, out of the porosities tested here. The porosity of 59.2% (MPS 272μm) showed lower contact values. NiTi tendon suture material was studied by implanting NiTi sutures into rabbit tendon and subcutaneous tissues for two, six, and twelve weeks. NiTi proved to be stronger than polyester, which served as control material. The encapsulating membrane was minimal with both materials, suggesting good biocompatibility in tendon tissue. The implantation did not affect the strength properties of either material. On the basis of the present studies, NiTi provides a possibility to develop new kinds of implants for correcting bone deformities, for filling bone defects in weight-bearing locations and a good candidate for a tendon suture material.

>Magister Scientiae - MSc / The fracture porosity and permeability of the Beaufort Seam 1 (BS1) and Ecca coal seams of the Waterberg Basin have been comprehensively characterised with the aid of geophysical wire‐line logs. The main aim of the thesis was to estimate the porosity and permeability of the coal seams using down‐hole wire‐line data; comparing results from injection falloff test to establish the validity of the technique as a fast an effective method. The study area is the largely under explored Karoo‐aged, fault bounded Waterberg basin Located in the Limpopo Province of South Africa. The study employed mainly the density and dual lateral resistivity logging data (Las format) from eight wells (WTB45, WTB48, WTB56, WTB58, WTB62, WTB65, WTB70 and WTB72). Density logging data was used for coal identification and fracture porosity estimation while fracture permeability was estimated from dual lateralog resistivity data. Analysis of fracture porosity required coal cementation indices and fracture width as an input parameter. These were estimated with the aid of water pump out test data, coal quality and gas analysis data provided by Anglo Coal in addition to the above mention logs. The collection of sheet coal model was used to represent anisotropic coal reservoirs with non‐uniform fracture system was used to represent these coals. The mathematical formulas used to estimate both fracture porosity and permeability took into account the above coal model. The theoretical formulas are a modification from both Darcy’s equation and Archie’s equations. The coal seams were encountered at depths ranging from 198m to 385m in the wells and were marked by low density and very high resistivity. From the estimated results the coal reservoirs are characterised by high cementation indices ranging from 0.82 to 2.42, very low fracture porosity and low fracture permeability. Estimated results show that coal reservoir fracture porosity ranged from 0.0002% to 0.33% for both BS1 and Ecca seams. Estimated results also show that coal reservoir permeability ranged from 0.0045mD to 6.05mD in the BS1 formation and from 0.01 to 0.107mD in the Ecca. Results when compared with those of injection falloff test shows that the estimated permeability is slightly lower as expected since the model did not account for coal anisopropy. The fracture permeability was found to decrease with increase in vitrinite content, coal rank, coal burial depth and increases with increase in inertinite content. On a basinal scale the model estimated permeability was found to increase slightly from the east to the west of the basin. The porosity decreases with increase cementation index for deeper coal seams and increases with increase cementation index for shallower coal seams.

Self-propagating High-temperature Synthesis (SHS) is the synthesis of solid materials by a reaction wave propagating into the initial reactants, typically two metals, which can alloy exothermically. Typically, experiments are performed with the reactants in powder form, with relatively low density. Recent experiments by Bacciochini et al. revealed much larger flame speeds in densified powders near TMD (theoritical maximum density), obtained by the cold spray process. The present thesis investigates why the flame speed increases dramatically with an increase in density of the powders. The investigation rests on the analytical model formulated by Makino by controlling how the variables are affected by changes in density. Flame speed measurements were performed in mixtures of nickel (Ni) and aluminum (Al) at different initial densities. The density was varied by controlling the cold-pressing of the samples inside metallic channels and tubes. Experiments were also performed in ball-milled powders, in order to permit comparison with the experiments performed by Bacciochini in these mixtures at nearly maximum densities. The measurements revealed that the flame speed increases with the initial density, with a discontinuous transition occurring at approximately 60% theoretical maximum density (TMD). This transition also corresponds to the point where the powders deform plastically during the compaction process, suggesting that the intimate contact between the particles is responsible for the flame speed increase. The flame speed dependence on powder density is attributed to the changes in the heat conductivity of the pressed powders. At high densities, where the powders have plastically deformed, the continuous structure yields conductivities close to the idealized solid matrix. At these high densities, the conductivity was modeled using the Effective Medium Theory (EMT). Analytical predictions of the flame speed, using available thermo-chemical data for the Al-Ni system were found in good agreement with the present experiments at high densities. At low densities, since Al-Ni is a mixture of loose powders, the EMT model is no longer applicable. Thus, the thermal conductivity was experimentally measured and then was fitted using the semi-empirical model suggested by Aivazov. Using this data, Makino's model predicts the correct flame speed dependence observed experimentally. The present thesis has thus established that the dependence of flame speed on density is due mainly to the changes in the structure and thermal conductivity of the powders.

This project studied the physical and chemical effects of typical impurities on CO2 storage using both experimental approaches and theoretical simulation. Results show that the presence of typical non-condensable impurities from oxyfuel combustion such as N2, O2, and Ar resulted in lower density than pure CO2, leading to decreased CO2 storage capacity and increased buoyancy in saline aquifers. In contrast, inclusion of condensable SO2 in CO2 resulted in higher density than pure CO2 and therefore increased storage capacity. These impurities also had a significant impact on the phase behaviours of CO2, which is important to CO2 transportation. Different effects on rock chemistry were detected with experimental systems containing pure CO2, CO2 with SO2, or CO2 with SO2 and O2 under conditions simulating that in a potential storage site. An equation was proposed to predict the effects of the rock chemistry on the porosity of rocks.

Orientador: Amauri Garcia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-07T13:54:54Z (GMT). No. of bitstreams: 1 Boeira_AlexandrePitol_D.pdf: 5616217 bytes, checksum: 09ba745cbcd2adadf17f39376225a70d (MD5) Previous issue date: 2006 / Resumo: A porosidade é um dos mais importantes defeitos encontrados em componentes fundidos. Neste trabalho, a macrossegregação e a formação de porosidade são investigadas por meio de modelagem numérica e experimentos de solidificação unidirecional vertical ascendente. As composições locais, ao longo dos lingotes, para ligas binárias de alumínio e cobre (AI-4,5%Cu, AI-6,2%Cu e AI-8,1 %Cu) são previstas pelo modelo de macrossegregação e servem de parâmetro de entrada para as simulações da correspondente microporosidade. Os efeitos da gravidade na redistribuição do soluto e na formação da microporosidade também são considerados pelo modelo. Um espectrômetro de tluorescência de raios X foi usado para determinar os perfis de segregação ao longo dos lingotes. As medidas de microporosidade foram realizadas através da análise picnométrica. Os perfis experimentais de segregação e de porosidade nos lingotes são comparados com as previsões teóricas fornecidas pelo modelo numérico, considerando um perfil do coeficiente de transferência de calor metal molde transitório, determinado experimentalmente. Observa-se uma excelente concordância entre os perfis simulados e experimentais de segregação inversa do cobre. A simulação da formação de porosidade, para canais anisotrópicos, mostra-se bastante alinhada com os resultados da análise experimental. Neste contexto, a fração volumétrica de poros apresenta uma tendência ascendente à medida que se distancia da base refrigerada / Abstract: Porosity is one of the most important defects in metaIs casting. In this research macrosegregation and porosity formation are investigated by a numerical modeling technique and by upward vertical unidirectional solidification experiments. The local composition, along the castings length of aluminum cooper binary alloys (AI-4.5 wt % Cu, AI-6.2 wt % Cu and AI-8.l wt % Cu) are predicted by the macrosegregation model and are used as an input parameter for simulation of the corresponding microporosity. The effects exerted by gravity upon the solute redistribution and microporosity formation are also encompassed by this model. X-ray fluorescence spectrometer was used to determine the segregation profiles along the castings. The measurement of microporosity was performed using picnometric analysis. The experimental segregation profiles and porosity evolution along the castings are compared with theoretical predictions furnished by the numerical mo deI, where the transient metal/mold heat transfer coefficient was experimentally determined. An excellent agreement between the simulated and experimental inverse copper profile has been observed. The simulation of porosity formation for anisotropic channels has fitted better the results of the experimental analysis. In this context, the volumetric fraction of pores has shown an ascending trend from the chill to the top of the ingot / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

>Magister Scientiae - MSc / This contribution engages in the evaluation of offshore sandstone reservoirs of the Central Bredasdorp basin, Block 9, South Africa using primarily petrophysical procedures. Four wells were selected for the basis of this study (F-AH1, F-AH2, F-AH4, and F-AR2) and were drilled in two known gas fields namely F-AH and F-AR. The primary objective of this thesis was to evaluate the potential of identified Cretaceous sandstone reservoirs through the use and comparison of conventional core, special core analysis, wire-line log and production data. A total of 30 sandstone reservoirs were identified using primarily gamma-ray log baselines coupled with neutron-density crossovers. Eleven lithofacies were recognised from core samples. The pore reduction factor was calculated, and corrected for overburden conditions. Observing core porosity distribution for all wells, well F-AH4 displayed the highest recorded porosity, whereas well F-AH1 measured the lowest recorded porosity. Low porosity values have been attributed to mud and silt lamination influence as well as calcite overgrowths. The core permeability distribution over all the studied wells ranged between 0.001 mD and 2767 mD. Oil, water, and gas, were recorded within cored sections of the wells. Average oil saturations of 3 %, 1.1 %, and 0.2 % were discovered in wells F-AH1, F-AH2, and F-AH4. Wells F-AH1 to F-AR2 each had average gas saturations of 61 %, 57 %, 27 %, and 56 % respectively; average core water saturations of 36 %, 42 %, 27 %, and 44 % were recorded per well.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第22088号 / エネ博第396号 / 新制||エネ||76(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 星出 敏彦, 教授 今谷 勝次, 教授 川那辺 洋 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

The aim of this master’s thesis was to evaluate cold spray technologies as an alternative method of repairing contact surfaces of parts, especially made of high-alloy manganese steels, to choose a suitable system of materials and to analyze the properties and structure of the produced coating. The thesis presents the basic of the mechanism of cold spray deposition, the described influence of basic process parameters on the structure and properties of metal coatings. Performed analysis of chemical composition, structure, porosity, hardness and strength of AISI H13 steel coating on a high-alloy manganese steel substrate. The described dependence of the structure and properties of a given coating on the heat treatment regime.

In this study, the freeze-thaw performance and other engineering properties of different cementitious mixtures containing Type I/II portland cement, Type IL (10) portland Limestone cement (PLC) and Coarse Ground cement (CG-P) with or without partial replacement of fly ash (Class F) were examined. The goal was to develop a concrete mixture with better or similar freeze-thaw durability without adversely affecting other engineering properties of concrete. Crucial engineering properties reviewed include compressive strength, splitting tensile strength, workability, the degree of hydration, setting time, shrinkage and resistivity. The study was divided into two parts, one consisting of mechanical testing of engineering properties including the freeze-thaw test. The second part consisted of microstructure study which involved detection and quantification of micro-cracks/defects using μ-CT and fluorescence microscopy. The results showed that the portland limestone cement in combination with fly ash demonstrated better or similar durability in comparison to the conventional portland cement concrete mixtures.