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Measuring the liquid velocity and turbulence parameters in multiphase flows is a challenging task. In general, measurements based on optical methods are hindered by the presence of the gas phase. In the present work, it is shown that this leads to a sampling bias. Here, particle image velocimetry (PIV) is used to measure the liquid velocity and turbulence in a bubble column for different gas volume flow rates. As a result, passing bubbles lead to a significant sampling bias, which is evaluated by the mean liquid velocity and Reynolds stress tensor components. To overcome the sampling bias a window averaging procedure that waits a time depending on the locally distributed velocity information (hold processor) is derived. The procedure is demonstrated for an analytical test function. The PIV results obtained with the hold processor are reasonable for all values. By using the new procedure, reliable liquid velocity measurements in bubbly flows, which are vitally needed for CFD validation and modeling, are possible. In addition, the findings are general and can be applied to other flow situations and measuring techniques.

Dans ce mémoire, deux problèmes liés aux écoulements multiphasiques compositionnels en milieux poreux ont été traités. La première partie est consacrée au développement d'une nouvelle approche alternative aux calculs flash, qui permet de résoudre les équations d'équilibre thermodynamique analytiquement. Cette méthode est basée sur des équations d'état (EOS) dissymétriques, ainsi, les comportements du gaz, du liquide et du fluide diphasique sont décrits par des EOS individuelles simples. La Capacité d'une EOS à capturer l'état diphasique est appelé : conditions de consistance. Ces conditions ont été formulées dans cette partie pour les systèmes multi-composants. La deuxième partie est consacrée au développement de la méthode de saturations négatives qui a été proposé précédemment par notre groupe pour le cas d'un mélange diphasique binaire. Tout d'abord, nous avons présenté la théorie analytique de la méthode pour les mélanges idéaux puis sa généralisation pour des mélanges réels avec un nombre arbitraire de composants chimiques et de phases. Nous avons obtenu les nouvelles équations multiphasiques uniformes qui contiennent des termes supplémentaires responsables de la diffusion et de la gravité à travers les interfaces de transition de phase / In this thesis, two problems related to compositional multiphase flow in porous media have been treated. The first part is devoted to develop a new approach which gives a form of equilibrium equations which can be solved analytically even for multi-component non ideal systems and even in the presence of capillary effects, which reduce significantly computational time. In this approach, separate behaviors of gas, liquid and two phase fluid may be described using very simple equations of state (EOS). Capacity of EOS?s to capture two phase state is called: consistency conditions. These conditions are formulated in this part for multi-components systems. The second part is devoted to develop the negative saturations method which was proposed earlier by our group for the case of two-phase binary mixtures. First, we have developed the mathematical theory of the method for ideal mixtures in 1D case. Next, we have generalized the method for the case of any number of phases and chemical components. We have obtained the new equivalent uniform multi-phase equations which contain additional non-classical terms responsible of diffusion and gravity across the interfaces of phase transition

Cette thèse est consacrée à l'étude de méthodes numériques pour la simulation des écoulements polyphasiques en milieu poreux, en vue de leur application à des problèmes d'ingénierie pétrolière ou environnementale. Nous présentons une formulation générique du modèle d'écoulements à nombre quelconque de composants présents dans un nombre quelconque de phases. Dans notre approche l'approximation des flux diffusifs (issus, par exemple, de la loi de Darcy) s'appuie sur de nouveaux schémas, appelés schémas gradient, qui ont plusieurs avantages sur les schémas industriels standard : ces derniers, qui sont des schémas volumes finis multi-points centrés aux mailles, ne sont généralement pas symétriques et convergent difficilement sur des cas à forts rapports d'anisotropie. Nous montrons en revanche que les schémas gradient conduisent naturellement à des approximations symétriques et convergentes. Parmi cette classe de schémas, nous étudions plus particulièrement le schéma "VAG" qui fait intervenir des inconnues au centre des mailles et aux sommets du maillage. Ce schéma conduit à la définition de flux entre le centre d'une maille et ses sommets, qui sont utilisés pour généraliser la méthode "VAG" au contexte polyphasique. Des tests numériques montrent alors que ce schéma est robuste, et conduit à un très bon compromis précision/coût, ce qui en fait un candidat idoine pour les applications industrielles. Nous présentons notamment un cas test, basé sur des observations de terrains, d'injection et de dissolution de CO2 dans la région proche d'un puits foré dans un aquifère salin. Nous montrons alors que le schéma numérique permet de simuler l'assèchement et la précipitation de minéral observée en pratique. Un chapitre de la thèse est enfin consacré à l'étude pratique et théorique d'une méthode numérique générique pour contrôler l'effet d'axe lors de l'utilisation de schémas industriels / This thesis is focused on numerical methods dedicated to the simulation of multiphase flow in porous media, involved in petroleum or environmental engineering. We present a generic formulation of the flow model which is able to take into account any number of components within any number of phases. In our approach the approximation of the diffusive fluxes (mainly resulting from Darcy's law) is based on new schemes, called gradient schemes, which show several advantages over the standard industrial numerical schemes : these schemes, which belong to the class of the cell-centred MultiPoint Flux Approximation finite volume schemes, are not symmetric and may lead to difficulties of convergence in the case of high anisotropy ratios. We indeed show that gradient schemes are naturally providing symmetric and convergent approximations. We particularly study the Vertex Approximate Gradient scheme (called the VAG scheme), whose discrete unknowns are the values at the cell centres and at the vertices of the mesh. This scheme implies the definition of fluxes between the centre of a given cell and its vertices, used for the extension of the scheme to multiphase flow. Numerical tests show the robustness and the accuracy of the method for a low computational cost, which enables the use of the VAG scheme in an industrial framework. A test case, based on experimental data of injection and dissolution of CO2 in the near-well region within a saline aquifer, shows the aptitude of the scheme for reproducing drying and salt precipitation, which are practically observed. Finally, a chapter of the thesis is devoted to the theoretical and practical study of a general numerical method for controlling Grid Orientation Effect in industrial simulators

Cette thèse est consacrée aux écoulements homogènes de bulles, ainsi qu'à leur couplage avec le transport d'un scalaire et la turbulence. Elle s'intéresse plus spécifiquement aux effets de taille finie, des interactions hydrodynamiques et de la microstructure de la suspension qui sont étudiés à l'aide de simulations numériques directes à l'échelle d'une seule bulle. La dynamique d'une suspension laminaire de bulles induite par la seule gravité est d'abord revisitée. L'influence de la fraction volumique sur la vitesse de dérive des bulles est établie analytiquement et numériquement pour une suspension parfaitement ordonnée, puis des ressemblances entre suspensions ordonnées et suspensions désordonnées sont mises en évidence. Ces résultats sont ensuite mis à profit pour la modélisation du transport d'un scalaire passif au sein d'une suspension laminaire, tel que décrit par une diffusivité effective tensorielle, et des différences essentielles entre systèmes ordonnés et systèmes désordonnés concernant le transport de scalaire sont mises en exergue. Enfin, la turbulence est prise en compte dans les simulations et son interaction avec une bulle de taille finie est caractérisée. Il est montré que le comportement dynamique d'une bulle de taille comparable à la microéchelle de Taylor ressemble qualitativement à celui d'une microbulle, avec, notamment, une préférence pour certaines régions caractéristiques de l'écoulement. Une définition de l'écoulement vu par la bulle compatible avec les modèles standards de masse ajoutée et de portance est finalement proposée / This thesis is devoted to the study of homogeneous bubbly flows and their coupling with scalar transport and turbulence. It focuses on the effects of finite size, hydrodynamic interactions, and suspension microstructure, which are investigated using direct numerical simulations at the bubble scale. The dynamics of laminar buoyancy-driven bubbly suspensions is first revisited. More specifically, the effect of volume fraction on the bubble drift velocity is clarified by connecting numerical results to theory for dilute ordered systems, and similarities between perfectly ordered and free disordered suspensions are evidenced. These results are then used for the modeling of passive scalar transport in laminar suspensions as described by an effective diffusivity tensor, and crucial differences between ordered and disordered systems with respect to scalar transport are highlighted. Lastly, turbulence is included in the simulations, and its interaction with a finite-size bubble is characterized. The behavior of a bubble as large as Taylor microscale is shown to share a number of common features with that of a microbubble, most notably, the flow sampled by the bubble is biased. A definition of the liquid flow seen by the bubble, as it enters in usual models for the added mass and the lift forces, is finally proposed

Operações de produção de petróleo, que utilizam sistemas de bombeamento centrífugo submerso, constantemente encontram a presença de gás livre nos poços, o que pode gerar ou agravar problemas como cavitação e falhas dinâmicas, quando o gás é succionado pela bomba. O separador gravitacional do tipo shroud invertido é uma solução possível para este problema nos casos de operação em poços direcionais de petróleo. O trabalho tem como objetivo apresentar um estudo do diâmetro das bolhas que ocorrem no interior de um separador gravitacional gás-líquido do tipo shroud invertido. A finalidade é o aprimoramento de um modelo fenomenológico do funcionamento deste tipo de separador, aplicado à indústria petrolífera, sendo que o modelo fenomenológico garante total separação de gás, fornecidas determinadas condições. O modelo prevê, através do cálculo da energia cinética turbulenta, o tamanho médio das bolhas carregadas para o seio do líquido por aeração no duto anular. Partindo de estudos anteriores, uma verificação do modelo fenomenológico foi feita utilizando um aparato experimental com misturas bifásicas ar-água e ar-óleo em três diferentes inclinações. O aparato possui dimensões radiais reais de um poço de petróleo offshore. Foi utilizado um sensor 3D ORM para a medição do tamanho médio (sauter) das bolhas arrastadas pelo líquido até a entrada do tubo de produção, em diversas combinações de vazões da mistura água-ar. Esta medição permite o ajuste das correlações que regem o modelo fenomenológico, no que diz respeito às equações dependentes do diâmetro teórico de bolhas arrastadas pela fase líquida. As descobertas provenientes deste estudo foram implementadas em um código computacional que será utilizado pela PETROBRAS, financiadora do projeto, para suas operações de bombeamento. / Oil mining operations powered by centrifugal submersible pumping systems suffer constant setbacks due to the presence of free gas in wells. Decompression in the reservoir liberates this gas in the form of bubbles that, upon reaching the suction end of the pump, cause cavitation and dynamic failures resulting in production and equipment losses. The Inverted-shroud gravitational separator is a possible solution to this problem. This work presents a study on diameters of bubbles that occur inside this separator. The goal is the improvement of the understanding of this kind of separator as well as the enhancement of a previously reported phenomenological model, which ensures total gas separation when the separator is installed in directional wells and under specific operational conditions. Empirically adjusted correlations are used to ensure that all entrained bubbles do not reach the pump. The model was tested for two-phase flows of water-air and oil-air mixtures using three different inclinations. Tests were performed with an experimental apparatus that simulates a pilot-scale well casing with an inverted-shroud separator installed. A 3D ORM particle-size sensor was employed in order to measure the average (sauter) diameter of entrained bubbles that are dragged by the liquid flow towards the end of the production tube. This investigation will be used to improve the reliability of the phenomenological model and reduce its dependency on a theoretical prediction of the bubble size. The findings were incorporated to the final version of an in-house gas separator design software developed at the request of PETROBRAS, the project funder and Inverted-shroud patent holder, for usage on its oil mining operations.

A medição de vazão de escoamentos multifásicos é uma necessidade constante em diversas atividades industriais como exploração de óleo e gás, controle de linhas de transporte de vapor e monitoramento de sistemas de resfriamento de usinas nucleares. Dentre os meios disponíveis para a realização da medição de vazão mássica, os dispositivos de medição de pressão diferencial constituem um dos métodos mais simples, sendo sua construção, aplicação e operação em escoamentos monofásicos bem conhecidas e definidas por normas técnicas. No entanto, sua aplicação tem sido estendida a escoamentos multifásicos, geralmente estando aliada a uma técnica adicional de medição de fração de vazio ou fração volumétrica das fases. Este trabalho descreve o estudo numérico de escoamentos multifásicos através de medidores de vazão baseados em pressão diferencial como placas de orifício e bocais de vazão de raio longo. Para tal, primeiramente foram conduzidas simulações de escoamentos monofásicos através de placas de orifício e bocais de vazão de raio longo na faixa de número de Reynolds 15.000 500.000. Os resultados de coeficiente de descarga obtidos foram quantitativamente comparados com os valores preditos por norma ISO, apresentando desvio máximo de aproximadamente 4, 9% para as placas e de 1,0% para os bocais. Em uma segunda etapa, escoamentos do tipo gás úmido (wet gas) através de placas de orifício foram simulados através de três abordagens diferentes. Os resultados de vazão mássica total obtidos foram comparados com dados experimentais fornecidos pela PETROBRAS. As abordagens que consideram o escorregamento entre as fases apresentaram previsões mais próximas dos experimentos, com desvio relativo médio de 3,9%, enquanto a modelagem homogênea apresentou um desvio médio de 6, 6%. Nestes estudos, foram também avaliadas as estruturas desenvolvidas no escoamento através de visualizações da distribuição de fases. São também apresentadas duas sugestões para complementação da caracterização de um escoamento multifásico: (1) a introdução da informação de fração de vazio na formulação apresentada por Paz (2011) e (2) a análise estatística do sinal de pressão diferencial em placas de orifício. Com relação ao primeiro item, comparações quantitativas com dados experimentais sugeriram que a alternativa apresentada é viável para operações de monitoramento da produção. Já o último estudo mostrou qualitativamente a influência da quantidade de líquido na flutuação da pressão diferencial / The flowrate measurement of multiphase flows is a constant need at many industrial activities such as oil and gas exploration, steam transport lines control and monitoring of nuclear plants cooling systems. Within the available means for performing flowrate measurement, the differential pressure devices constitute one of the simplest methods, with their construction, application and operation in single phase flows being well known and defined by technical standards. However, their application has been extended to multiphase flows, usually being allied to a void fraction or phase volume fraction measurement technique. This work describes a numerical study of multiphase flows through differential pressure-based flowrate meters such as orifice plates and long radius nozzles. Firstly simulations of single phase flows through orifice plates and long radius nozzles were conducted in the Reynolds number range 15.000500.000. The obtained results of discharge coefficients were quantitatively compared to ISO Standard predicted values, showing a maximum deviation of approximately 4,9% for the orifice plates and of 1,0% for the nozzles. In a second stage, wet gas flows through orifice plates were simulated by means of three approaches. The calculated results of total mass flowrate were compared to experimental data provided by PETROBRAS. The approaches that considered the slip between phases provided the closest results to the experiments, with a mean relative error of 3, 9%, while the homogeneous modeling presented an error of 6, 6%. In these studies, the structures developed within the domain were also evaluated through the visualization of the phases distribution. Two suggestions for complementing the characterization of a multiphase flow are presented: (1) the introduction of void fraction information into the formulation presented by Paz (2011) and (2) the statistical analysis of the orifice plate pressure drop signal. Regarding the first item, quantitative comparison with experimental data suggested that the presented alternative is viable for production monitoring operations. The last study qualitatively revealed the influence of the liquid loading in the pressure drop fluctuation.

[pt] Cerca de 50 por cento das reservas brasileiras de hidrocarbonetos estão localizadas na plataforma continental em lâminas de água superiores a mil metros. As temperaturas congelantes do fundo do mar tornam os problemas inerentes ao escoamento da produção de petróleo, ainda mais críticos. Entretanto, os desafios da garantia de escoamento, não são os únicos obstáculos para a produção de petróleo em águas ultra-profundas. Além dos aspectos relacionados à geologia e fatores econômicos, a decisão de desenvolvimento de um campo de petróleo no mar, adotando completação submarina ou seca, precisa ser respaldada por uma análise criteriosa dos problemas relacionados com a garantia de escoamento, principalmente em locações de águas profundas e ultra- profundas. Nestes cenários, a maior variação da energia potencial e conseqüente intensificação do efeito Joule-Thomson, contribuem de uma forma bem mais significativa para a queda de temperatura e pressão. Este trabalho objetiva promover a comparação entre um sistema de produção usando poços direcionais de grande afastamento, produzindo para uma unidade de completação seca e um sistema adotando poços com completação submarina, a 850, 1.550 e 2.300m de lâmina de água, avaliando os efeitos das perdas de carga e calor em um fluxo multifásico. Com o uso de completação molhada, é avaliada a máxima distância viável entre a zona produtora e a plataforma de produção, de forma a permitir o fluxo de hidrocarbonetos sem formação de cristais de parafina. Com base nos resultados alcançados, podemos tirar algumas conclusões importantes quanto à tendência dos sistemas de produção em águas profundas e ultra- profundas, que nortearão no futuro próximo o desenvolvimento de campos de petróleo na plataforma continental brasileira. / [en] Around 50 percent of the Brazilian reserves of hydrocarbons are located in the continental platform in water depths with more than one thousand meters. The freezing temperatures of the sea bottom make problems related to oil production, even more critical. However, the flow assurance challenges are not the only obstacles for the oil production in ultra-deep waters. Besides the aspects related to the geology and economical factors, the decision of development of an offshore oil field adopting a system with wet completion or with dry completion, needs to be supported by discerning analyses of the problems related to flow assurance aspects, mainly in deep and ultra-deep water locations. In these scenarios, a larger variation of the potential energy and consequent intensification of the Joule-Thomson effect, contribute in a much more significant way to the temperature and pressure drops. This work aims to promote the comparison between an oil production system using extended reach wells with a dry completion unit and another system with wet completion, at 850, 1.550 and 2.300m of water depth, evaluating the effects of pressure drop and heat loss in a multiphase flow. Using wet completion, it is evaluated the maximum feasible distances between the producing zone of the formation and the floating production unit, allowing the flow of hydrocarbons without interruption by the formation of paraffin crystals. Based on the reached results, we can reach some important conclusions regarding trend of production systems in deep and ultra-deep water, that will guide the development of oil fields in the near future in the Brazilian continental platform.

L'atténuation du changement climatique est l'un des défis majeurs de notre époque. Les émissions anthropiques de gaz à effet de serre ont augmenté de façon continue depuis la révolution industrielle, provoquant le réchauffement climatique. Un ensemble de technologies très diverses doivent être mises en œuvre pour respecter les accords internationaux relatifs aux émissions de gaz à effet de serre. Certaines d'entre elles ont recours au sous-sol pour le stockage de diverses substances. Cette thèse traite plus particulièrement de la dynamique du stockage souterrain du dioxyde de carbone (CO2) et de l'hydrogène (H2). Des modèles numériques de transport réactif et multiphasiques ont été élaborés pour mieux comprendre la migration et les interactions des fluides dans des milieux poreux de stockage souterrain. Ils fournissent des recommandations pour améliorer l'efficacité, la surveillance et la sécurité du stockage. Trois modèles sont présentés dans ce document, dont deux dans le domaine du captage et du stockage du CO2 (CCS pour Carbon Capture and Storage), et le troisième s'appliquant au stockage souterrain de l'hydrogène (UHS pour Underground Hydrogen Storage). Chacun d'entre eux traite plus spécifiquement un aspect de la recherche : Modèle multiphasique appliqué au CCS L'efficacité et la sécurité à long terme du stockage du CO2 dépend de la migration et du piégeage du panache de CO2 flottant. Les grandes différences d'échelles temporelles et spatiales concernées posent de gros problèmes pour évaluer les mécanismes de piégeage et leurs interactions. Dans cet article, un modèle numérique dynamique diphasique a été appliqué à une structure aquifère synclinale-anticlinale. Ce modèle est capable de rendre compte des effets de capillarité, de dissolution et de mélange convectif sur la migration du panache. Dans les aquifères anticlinaux, la pente de l'aquifère et la distance de l'injection à la crête de l'anticlinal déterminent la migration du courant gravitaire et, donc, les mécanismes de piégeage affectant le CO2. La structure anticlinale arrête le courant gravitaire et facilite l'accumulation du CO2 en phase libre, en dessous de la crête de l'anticlinal, ce qui stimule la mise en place d'une convection et accélère donc la dissolution du CO2. Les variations de vitesse du courant gravitaire en raison de la pente de l'anticlinal peuvent provoquer la division du panache et une durée différente de résorption du panache en phase libre, qui dépend de l'endroit de l'injection. / Climate change mitigation is one of the major challenges of our time. The anthropogenic greenhouse gases emissions have continuously increased since industrial revolution leading to global warming. A broad portfolio of mitigation technologies has to be implemented to fulfill international greenhouse gas emissions agreements. Some of them comprises the use of the underground as a storage of various substances. In particular, this thesis addresses the dynamics of carbon dioxide (CO2) and hydrogen (H2) underground storage. Numerical models are a very useful tool to estimate the processes taking place at the subsurface. During this thesis, a solute transport in porous media module and various multiphase flow formulations have been implemented in COMSOL Multiphysics (Comsol, 2016). These numerical tools help to progress in the understanding of the migration and interaction of fluids in porous underground storages. Three models that provide recommendations to improve the efficiency, monitoring and safety of the storages are presented in this manuscript: two in the context of carbon capture and storage (CCS) and one applied to underground hydrogen storage (UHS). Each model focus on a specific research question: Multiphase model on CCS. The efficiency and long-term safety of underground CO2 storage depend on the migration and trapping of the buoyant CO2 plume. The wide range of temporal and spatial scales involved poses challenges in the assessment of the trapping mechanisms and the interaction between them. In this chapter a two-phase dynamic numerical model able to capture the effects of capillarity, dissolution and convective mixing on the plume migration is applied to a syncline-anticline aquifer structure. In anticline aquifers, the slope of the aquifer and the distance of injection to anticline crest determine the gravity current migration and, thus, the trapping mechanisms affecting the CO2. The anticline structure halts the gravity current and promotes free-phase CO2 accumulation beneath the anticline crest, stimulating the onset of convection and, thus, accelerating CO2 dissolution. Variations on the gravity current velocity due to the anticline slope can lead to plume splitting and different free-phase plume depletion time is observed depending on the injection location. Injection at short distances from the anticline crest minimizes the plume extent but retards CO2 immobilization. On the contrary, injection at large distances from anticline crest leads to large plume footprints and the splitting of the free-phase plume. The larger extension yields higher leakage risk than injection close to aquifer tip; however, capillary trapping is greatly enhanced, leading to faster free-phase CO2 immobilization. Reactive transport model on convective mixing in CCS. Dissolution of carbon-dioxide into formation fluids during carbon capture and storage (CCS) can generate an instability with a denser CO2-rich fluid located above the less dense native aquifer fluid. This instability promotes convective mixing, enhancing CO2 dissolution and favouring the storage safety.