Catalisadores baseados em óxidos de cério (CeOx, 3/2≤ x ≤ 2) como suporte são utilizados em várias reações de alto interesse econômico, por exemplo as reações de catalizadores de três-vias. Sabe-se que é possível melhorar as propriedade catalíticas da céria, através da mistura com óxido de zircônio e com a adição de partículas metálicas na superfície do material. Entretanto, a deposição de átomos de Zr sobre CeO2(111) é pouco explorada apesar de já ter sido utilizada para a síntese de nanopartículas de Ag de tamanho controlado. Uma das particularidades dos sistemas Zr/CeO2(111) é formar ilhas altura entre 1,5 e 3,0 Å sobre a superfície da céria que são sugeridas na literatura com camadas de Zr-O e O-Zr-O. Entretanto, a natureza e magnitudes das interações entre Zr e CeO2(111) ainda não são totalmente conhecidas, bem como as modificações causadas pelo Zr na superfície de CeO2 e os mecanismos que controlam a oxidação do Zr e a formação de ZrO2 na superfície. Visando entender as interações Zr/CeO2(111) e a formação de ZrO2 sobre CeO2(111), realizou-se um estudo teórico da adsorção de n (1 ≤n ≤ 4) adatomos de Zr sobre CeO2(111), e da formação de ZrO2 sobre CeO2(111). As análises de carga indicam transferências de carga do adatomos de Zr para a superfície e mudança no estado de oxidação das espécies. Os Zr se oxidam á Zr4+ e interagem com O2- da superfície, onde quatro cátions Ce4+ se reduzem á Ce3+. Analises energéticas indicam que o processo é muito estabilizante, mais de 10 eV por Zr. Com o aumento da quantidade n de adatomos de Zr na superfície, observa-se 4 × n reduções de Ce4+ e migrações de O2- de dentro da superfície para próximo dos Zr4+, formando agregados de ZrO2 sobre a superfície. A migração de O se deve a dois fatores, a interação dos O2- com Zr4+ no agregado é mais estável do que a interação dos O2- com Ce3+ dentro da superfície, e a migração de O diminuir a tensão causada pelo maior raio do Ce3+ em relação ao Ce4+. Em adição, foi encontrado uma tendência de estabilidade para os Zr4+ migrarem para sítios Ce dentro da superfície, devido a maior quantidade de coordenações Zr-O e a redução da tensão criada pelos Ce3+. / Cerium oxides (CeOx, 3/2≤ x ≤ 2) based catalysts are employed in several reactions with high economic interest, such as the reaction in three-way-catalysts. It is well know that is possible to improve the ceria catalytic properties, by mixing with zirconium oxide and adding metallic particles over the material surface. Meanwhile, the deposition of Zr atoms over CeO2(111) is little explored although it has already been used for synthesis Ag nanoparticles of controlled size. One of the particularities of the Zr/CeO2(111) systems is to form islands of height between 1,5 and 3,0 Å on the surface of the ceria, which are suggested in the literature to be Zr-O and O-Zr-O layers. However, the nature and magnitudes of interactions between Zr and CeO2 surface are little know, as well as the CeO2 modifications induced by Zr and the mechanisms for Zr oxidation and ZrO2 formation over the surface. Aiming to understand the Zr-CeO2(111) interactions and the ZrO2 formation over the CeO2(111), this mastering project perform a theoretical study of n (1 ≤ n ≤ 4) Zr adatoms absorption over CeO2(111), and the ZrO2 formation over CeO2(111). The charge analysis indicated charge transfer from Zr adatons to the surface together with change in species oxidation state. The Zr oxidize to Zr4+ and interact with surface O2- , where four Ce4+ cations reduce to Ce3+. Energetic analysis pointed out that the process is very stabilizing, more than 10 eV per Zr adatom. With the increase of quantity n of Zr adatoms over the surface, it is observer 4 × n Ce4+ reductions and O2- migrations from inside surface to close the Zr4+, forming ZrO2 aggregates over the surface. The O migration occurs because of two reasons, the O2- interaction with Zr4+ in the agregate is more stabilizer than the interaction of O2- with Ce3+ inside the surface, and the O migration decrease the strain produced bue to the radius of Ce3+ being greater than the Ce4+ radius. In addition, was found a stability trend for Zr4+ to migrate to inside surface Ce sites, due of the more Zr-O coordinations and release of the strain induced by Ce3+.

Catalisadores baseados em óxidos de cério (CeOx, 3/2≤ x ≤ 2) como suporte são utilizados em várias reações de alto interesse econômico, por exemplo as reações de catalizadores de três-vias. Sabe-se que é possível melhorar as propriedade catalíticas da céria, através da mistura com óxido de zircônio e com a adição de partículas metálicas na superfície do material. Entretanto, a deposição de átomos de Zr sobre CeO2(111) é pouco explorada apesar de já ter sido utilizada para a síntese de nanopartículas de Ag de tamanho controlado. Uma das particularidades dos sistemas Zr/CeO2(111) é formar ilhas altura entre 1,5 e 3,0 Å sobre a superfície da céria que são sugeridas na literatura com camadas de Zr-O e O-Zr-O. Entretanto, a natureza e magnitudes das interações entre Zr e CeO2(111) ainda não são totalmente conhecidas, bem como as modificações causadas pelo Zr na superfície de CeO2 e os mecanismos que controlam a oxidação do Zr e a formação de ZrO2 na superfície. Visando entender as interações Zr/CeO2(111) e a formação de ZrO2 sobre CeO2(111), realizou-se um estudo teórico da adsorção de n (1 ≤n ≤ 4) adatomos de Zr sobre CeO2(111), e da formação de ZrO2 sobre CeO2(111). As análises de carga indicam transferências de carga do adatomos de Zr para a superfície e mudança no estado de oxidação das espécies. Os Zr se oxidam á Zr4+ e interagem com O2- da superfície, onde quatro cátions Ce4+ se reduzem á Ce3+. Analises energéticas indicam que o processo é muito estabilizante, mais de 10 eV por Zr. Com o aumento da quantidade n de adatomos de Zr na superfície, observa-se 4 × n reduções de Ce4+ e migrações de O2- de dentro da superfície para próximo dos Zr4+, formando agregados de ZrO2 sobre a superfície. A migração de O se deve a dois fatores, a interação dos O2- com Zr4+ no agregado é mais estável do que a interação dos O2- com Ce3+ dentro da superfície, e a migração de O diminuir a tensão causada pelo maior raio do Ce3+ em relação ao Ce4+. Em adição, foi encontrado uma tendência de estabilidade para os Zr4+ migrarem para sítios Ce dentro da superfície, devido a maior quantidade de coordenações Zr-O e a redução da tensão criada pelos Ce3+. / Cerium oxides (CeOx, 3/2≤ x ≤ 2) based catalysts are employed in several reactions with high economic interest, such as the reaction in three-way-catalysts. It is well know that is possible to improve the ceria catalytic properties, by mixing with zirconium oxide and adding metallic particles over the material surface. Meanwhile, the deposition of Zr atoms over CeO2(111) is little explored although it has already been used for synthesis Ag nanoparticles of controlled size. One of the particularities of the Zr/CeO2(111) systems is to form islands of height between 1,5 and 3,0 Å on the surface of the ceria, which are suggested in the literature to be Zr-O and O-Zr-O layers. However, the nature and magnitudes of interactions between Zr and CeO2 surface are little know, as well as the CeO2 modifications induced by Zr and the mechanisms for Zr oxidation and ZrO2 formation over the surface. Aiming to understand the Zr-CeO2(111) interactions and the ZrO2 formation over the CeO2(111), this mastering project perform a theoretical study of n (1 ≤ n ≤ 4) Zr adatoms absorption over CeO2(111), and the ZrO2 formation over CeO2(111). The charge analysis indicated charge transfer from Zr adatons to the surface together with change in species oxidation state. The Zr oxidize to Zr4+ and interact with surface O2- , where four Ce4+ cations reduce to Ce3+. Energetic analysis pointed out that the process is very stabilizing, more than 10 eV per Zr adatom. With the increase of quantity n of Zr adatoms over the surface, it is observer 4 × n Ce4+ reductions and O2- migrations from inside surface to close the Zr4+, forming ZrO2 aggregates over the surface. The O migration occurs because of two reasons, the O2- interaction with Zr4+ in the agregate is more stabilizer than the interaction of O2- with Ce3+ inside the surface, and the O migration decrease the strain produced bue to the radius of Ce3+ being greater than the Ce4+ radius. In addition, was found a stability trend for Zr4+ to migrate to inside surface Ce sites, due of the more Zr-O coordinations and release of the strain induced by Ce3+.

Carbon dioxide capture and storage (CCS) is considered one of the key technologies for reducing atmospheric emissions of CO₂ from human activities (IPCC, 2005). The scale of potential deployment of CCS is enormous spanning manufacturing, power generation and hydrocarbon extraction worldwide. Uncertainty, cost-benefit challenges, market barriers and failures, and promotion and regulation of infrastructure are the main obstacles for deploying CCS technology in a broad scale. In a CCS project, it is the operator’s responsibility to guarantee the CO₂ containment while complying with environmental regulations and CO₂ contractual requirements with the source emitter. Acquiring new information (e.g. seismic, logs, production data, etc.) about a particular field can reduce the uncertainty about the reservoir properties and can (but not necessarily) influence the decisions affecting the deployment of a CCS project. The main objective of this study is to provide a decision-analysis framework to quantify the Value of Information (VOI) in a CCS project that faces uncertainties about permeability values in the reservoir. This uncertainty translates into risks of CO₂ migration out of the containment zone (or lease zone), non-compliance with contractual requirements on CO₂ storage capacity, and leakage of CO₂ to sources of Underground Source of Drinking Water (USDW). The field under analysis has been idealized based on a real project located in Texas. Subsurface modeling of the upper Frio Formation (injection zone) was conducted using well logs, field-specific GIS data, and other relevant published literature. The idealized model was run for different scenarios with different permeability distributions. The VOI was quantified by defining prior scenarios based on the current knowledge of a reservoir, contractual requirements, and regulatory constraints. The project operator has the option to obtain more reliable estimates of permeability, which will help to reduce the uncertainty of the CO₂ behavior and storage capacity of the formation. The accuracy of the information gathering activities is then applied to the prior probabilities (Bayesian inference) to infer the value of such data. / text

Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12680号 / 論工博第4082号 / 新制||工||1548(附属図書館) / 29813 / (主査)教授 田中 庸裕, 教授 江口 浩一, 教授 安部 武志 / 学位規則第4条第2項該当

Characterizing natural and man-made fracture networks is fundamental to predicting the storage capacity and pathways for flow of both carbonate and shale reservoirs. The goal of this study is to determine the seismic response specifically to networks of fractures clustered closely together through the analysis of seismic wavefield scatter, directional phase velocities, and amplitude attenuation. To achieve this goal, finite element modeling techniques are implemented to allow for the meshing of discontinuous fracture interfaces and, therefore, provide the most accurate calculation of seismic events from these irregular surfaces. The work presented here focuses on the center layer of an isotropic model that is populated with two main phases of fracture network alteration: a single large-scale cluster and multiple smaller-scale clusters. Phase 1 first confirms that the seismic response of a single idealized vertically fractured cluster is distinct crosscutting energy within a seismogram. Further investigation shows that, as fracture spacing within the cluster decreases, the depth at which crosscutting energy appears exponentially increases, placing it well below the true location of the cluster. This relationship holds until 28% of the fractures are moved from their uniformly spaced locations to random locations within the cluster. The vertical thickness of the cluster has little effect on the location or strength or the crosscutting signature. Phase 2 shows that, although clusters of more randomly spaced fractures mask crosscutting energy, a marked decrease in amplitude coinciding with a bend in the wavefront produces a heterogeneous anisotropic seismic response. This amplitude decay and heterogeneous anisotropy is visible until cluster spacing drops below one half of the wavelength or the ratio of fractured material to matrix material within a cluster drops below 37%. Therefore, the location of an individual fracture cluster can be determined from the location of amplitude decay, heterogeneous anisotropy, and crosscutting energy. Furthermore, the density of the cluster can be determined from the degree of amplitude decay, the angle of heterogeneous anisotropy, and the depth of cross-cutting energy. These relationships, constrained by limits on their detectability, can aid fracture network interpretation of real seismic data. / text

Concerns about elevated atmospheric carbon dioxide (CO 2 ) and the effect on global climate have created proposals for the reduction of carbon emissions from large stationary sources, such as power plants. Carbon dioxide capture and sequestration (CCS) in deep geologic units is being considered by Florida electric-utilities. Carbon dioxide-enhanced oil recovery (CO 2 -EOR) is a form of CCS that could offset some of the costs associated with geologic sequestration. Two potential reservoirs for geologic sequestration were evaluated in south-central and southern Florida: the Paleocene Cedar Keys Formation/Upper Cretaceous Lawson Formation (CKLIZ) and the Lower Cretaceous Sunniland Formation along the Sunniland Trend (Trend). The Trend is a slightly arcuate band in southwest Florida that is about 233 kilometers long and 32 kilometers wide, and contains oil plays within the Sunniland Formation at depths starting around 3,414 meters below land surface, which are confined to mound-like structures made of coarse fossil fragments, mostly rudistids. The Trend commercial oil fields of the South Florida Basin have an average porosity of 16% within the oil-producing Sunniland Formation, and collectively have an estimated storage capacity of around 26 million tons of CO 2 . The Sunniland Formation throughout the entire Trend has an average porosity of 14% and an estimated storage capacity of about 1.2 billion tons of CO 2 (BtCO2 ). The CKLIZ has an average porosity of 23% and an estimated storage capacity of approximately 79 BtCO 2 . Porous intervals within the CKLIZ and Sunniland Formation are laterally homogeneous, and low-permeability layers throughout the units provide significant vertical heterogeneity. The CKLIZ and Sunniland Formation are considered potentially suitable for CCS operations because of their geographic locations, appropriate depths, high porosities, estimated storage capacities, and potentiallyeffective seals. The Trend oil fields are suitable for CO 2 -EOR in the Sunniland Formation due to appropriate injected-CO 2 density, uniform intergranular porosity, suitable API density of formation-oil, sufficient production zones, and adequate remaining oil-in-place following secondary recovery. In addition to these in-depth investigations of the CKLIZ and Sunniland Formation, a more-cursory assessment of deep geologic units throughout the state of Florida, which includes rocks of Paleocene and Upper Cretaceous age through to rocks of Ordovician age, shows additional units in Florida that may be suitable for CO 2 -EOR and CCS operations. Furthermore, this study shows that deep geologic units throughout Florida potentially have the capacity to sequester billions of tons of CO 2 for hundreds of fossil-fuel-fired power plants. Geologic sequestration has not yet been conducted in Florida, and its implementation could prove useful to Florida utility companies, as well as to other energy-utilities in the southeastern United States.

The combustion of fossil fuels results in the release of carbon dioxide to the atmosphere, a known greenhouse gas. Evidence suggests that “most of the observed increase in global average temperatures…is very likely due to the observed increase in anthropogenic greenhouse gas concentrations” (IPCC, 2007). One solution currently being examined is carbon capture and storage (CCS). The advantage of CCS is that it does not require an actual reduction in the amount of carbon dioxide emissions created, but reduces emissions to the atmosphere by storing the greenhouse gases in the subsurface. Fundamentally, CCS works in the reverse of oil and gas production. Instead of extracting fluids from the subsurface, CCS injects carbon dioxide (CO2) into the pore spaces of developed oil and gas reservoirs, saline aquifers, or coal bed seams (Bachu, 2007), where it exists in a dense but low-viscosity phase (Supercritical state). The Gulf Coast Carbon Center, based at the University of Texas at Austin’s Bureau of Economic Geology, is currently evaluating the State of Texas Offshore Lands (STOL) in the Gulf of Mexico (GOM) in order to evaluate the carbon-storage capacity in the state owned lands. “Capacity is defined as the volume fraction of the subsurface within a stratigraphic interval available for [CO2] sequestration” (Hovorka, 2004). There are a variety of methods currently used to calculate capacity. With so many options, how does a project decide which method to employ in determining capacity? This paper discusses the methods, presents an analysis of the benefits and drawbacks of the various methods, and develops a process for future projects to utilize in determining which methodology to employ. Additionally, storage capacity is calculated using the various methods presented, in order to compare the methods and understand their various advantages and drawbacks. Reservoir specific simulations are expected to predict smaller capacities in comparison to more broad static methods. This will provide end member predictions of capacity, shedding light on what can be expected in best case and worst case scenarios. The lessons learned from this study can be applied to future endeavors and formations all over the world. / text

L’économie d’énergie dans le bâtiment est devenue une question préoccupante d’envergure internationale. Le secteur du bâtiment en effet, est l’un des plus énergétivores avec par exemple plus de 43% du total d’énergie produite en France, mais aussi l’un des plus polluants avec environs, 23% des émissions de gaz à effet de serre. Avec l’accroissement des ménages, et la demande par conséquent d’énergie, les problèmes ci-dessus évoqués vont décupler et devenir rapidement ingérables les années à venir, si aucune mesure n’est prise. Ainsi, pour faire face à la situation, plusieurs stratégies sont mises en œuvre aux fins de réaliser l’économie d’énergie dans le bâtiment. Il y a le volet prédiction d’énergie qui oeuvre pour l’énergie juste heure après heure ; le volet recherche et élimination de ponts thermiques, afin de réduire au minimum les déperditions d’énergie représentant environ 30% de la consommation d’énergie ; et le volet conservation d’énergie dans les parois de bâtiment pour sa réutilisation future. Notre thèse s’est penchée sur les deux derniers volets en proposant différentes méthodes de CND et des traitements appropriés permettant la mise en évidence de défauts dans les structures de bâtiment. Des approches d’estimation de matrice de transfert ont été aussi abordées, pour permettre de prévoir le comportement thermique du bâtiment soumis à une sollicitation quelconque. La grande contribution de cette thèse concerne la mise au point d’une technique de mesure de capacité de stockage in-situ. Elle est importante, car il existe quantité de logiciels proposant la composition des structures d’un bâtiment pour une capacité de stockage d’énergie donnée. Mais il n’existe aucune méthode permettant de confirmer ou d’infirmer les résultats issus de calculs artificiels. Cette thèse apporte une solution à cette situation en proposant une méthode simple, sans encombrement, facile à mettre en œuvre et offrant un résultat satisfaisant. / Energy saving in buildings has become a major international issue. Indeed, the building sector is one the most energy consuming sectors, for instance in France it consumes more than 43% of the total produced energy, and also it is one of the most polluter with around 23% of the green house gas emissions. As more and more households appear, the energy demand will increase and the above mentioned problems will be ten times more sever making them unmanageable in the upcoming years if no measure is taken. Thus, to face this situation, many strategies have been setup in order to achieve some energy saving in buildings. Among these strategies we find the energy prediction part which deals with hour by hour right energy; the research and elimination part of thermal bridges which its main objective is to reduce as much as possible the energy losses representing around 30% of the energy consumption; and the energy conservation part in wall buildings for future recycling. Our thesis focuses on the last two parts by proposing different methods of CND as well as appropriate survey treatments which allow to highlight structural failure in buildings. Transfer matrix estimation approaches have been used to predict the thermal behavior for a building that is being put under any kind of stress.The main contribution of this thesis concerns the developing of an in-situ storage capacity measuring technique. This is important since there are many softwares proposing the structural composition of a building for a given amount of energy. Nevertheless, there isn’t any method available for confirming or invalidating the results coming from artificial calculations. This thesis brings a solution to this situation by proposing a simple method, with no obstacles, easy to setup and with satisfactory results.

Philosophiae Doctor - PhD / The Table Mountain Group (TMG) Aquifer is a huge aquifer system which may provide large bulk water supplies for local municipalities and irrigation water for agriculture in the Western Cape and Eastern Cape Provinces in South Africa. In many locations, water pressure in an aquifer may force groundwater out of ground surface so that the borehole drilled into the aquifer would produce overflow without a pump. Appropriate testing and evaluation of such artesian aquifers is very critical for sound evaluation and sustainable utilization of groundwater resources in the TMG area. However, study on this aspect of hydrogeology in TMG is limited. Although the flow and storage of TMG aquifer was conceptualised in previous studies, no specific study on artesian aquifer in TMG was made available. There are dozens of flowing artesian boreholes in TMG in which the pressure heads in the boreholes are above ground surface locally. A common approach to estimate hydraulic properties of the aquifers underneath is to make use of free-flowing and recovery tests conducted on a flowing artesian borehole. However, such testing approach was seldom carried out in TMG due to lack of an appropriate device readily available for data collection. A special hydraulic test device was developed for data collection in this context. The test device was successfully tested at a flowing artesian borehole in TMG. The device can not only be used to measure simultaneous flow rate and pressure head at the test borehole, but also be portable and flexible for capturing the data during aquifer tests in similar conditions like artesian holes in Karoo, dolomite or other sites in which pressure head is above ground surface. The straight-line method proposed by Jacob-Lohman is often adopted for data interpretation. However, the approach may not be able to analyse the test data from flowing artesian holes in TMG. The reason is that the TMG aquifers are often bounded by impermeable faults or folds at local or intermediate scale, which implies that some assumptions of infinite aquifer required for the straight-line method cannot be fulfilled. Boundary conditions based on the Jacob-Lohman method need to be considered during the simulation. In addition, the diagnostic plot analysis method using reciprocal rate derivative is adapted to cross-check the results from the straight-line method. The approach could help identify the flow regimes and discern the boundary conditions, of which results further provide useful information to conceptualize the aquifer and facilitate an appropriate analytical method to evaluate the aquifer properties. Two case studies in TMG were selected to evaluate the hydraulic properties of artesian aquifers using the above methods. The transmissivities of the artesian aquifer in TMG range from 0.6 to 46.7 m2/d based on calculations with recovery test data. Storativities range from 10-4 to 10-3 derived from free-flowing test data analysis. For the aquifer at each specific site, the transmissivity value of the artesian aquifer in Rawsonville is estimated to be 7.5–23 m2/d, with storativity value ranging from 2.0×10-4 to 5.5×10-4. The transmissivity value of the artesian aquifer in Oudtshoorn is approximately 37 m2/d, with S value of 1.16×10-3. The simulation results by straight-line and diagnostic plot analysis methods, not only imply the existence of negative skin zone in the vicinity of the test boreholes, but also highlight the fact that the TMG aquifers are often bounded by impermeable faults or folds at local or intermediate scale. With the storativity values of artesian aquifers derived from data interpretation, total groundwater storage capacity of aquifers at two case studies was calculated. The figures will provide valuable information for decision-makers to plan and develop sustainable groundwater utilization of artesian aquifers in local or intermediate scales. With the hydraulic test device readily available for data collection, more aquifer tests can be carried out in other overflow artesian boreholes in TMG. It becomes feasible to determine the hydraulic properties of artesian aquifers for the entire TMG. Thereof quantification of groundwater resources of artesian aquifers in TMG at a mega-scale becomes achievable. This would also contribute towards global research initiative for quantification of groundwater resources at a mega-scale.

>Magister Scientiae - MSc / Hydrogeological characterization of an aquifer system is a first step to determine groundwater quantity, yield potential, socio-economic value, storage capacity and aquifer transmissivity properties of an aquifer as a water resource. Derivative analysis is a technique that has been used to understand groundwater flow systems. This is mainly because derivative analysis of pumping test data and curve matching improves the understanding of aquifer types and hydrogeologic setting of a study site. Time vs drawdown curves produced through pumping tests serve as the most useful tools to analyse aquifer characteristics. The study was conducted through performing pumping test in boreholes of hospital facilities in the Western Cape drilled on the TMG and Malmesbury formation. / 2023