This thesis presents results of a successful simulation study using CO2-EOR technique to enable production from an offshore heavy oil field, named here as Omega, which is located offshore West Africa at a water depth around 2000 m. The findings and contributions to knowledge are outlined below: 1. Long distance CO2 transportation offshore – The solution to the space and weight constraints offshore with respect to CO2-EOR, is a tie-back via long distance CO2 dense phase transportation from onshore to offshore. 2. Cold heavy oil production (CHOP) using CO2-EOR technique - Based on conditions investigated, Miscible Displacement was found to be more efficient for deepwater production. However, Immiscible Displacement can offer greater reliability with regards to CO2 sequestration. 3. CO2 sequestration during CHOP using CO2-EOR technique – Lower CO2 may be released post start-up operation, followed by gradual decline of CO2 retention after the production peak. CO2 retention increases with increasing reservoir pressure, starting with 17.7 % retention at 800 psig to 32.8 % at 5000 psig, based on peak production analysis. 4. Techno-economic Evaluation – Miscible displacement is asssociated with higher cash flow stream that extend throughout the lifetime of the asset due to continuous production while Immiscible Displacement has a longer payback period (in order of 22 years) due to the time lag between the CO2 injection and the incremental heavy oil production. 5. Mathematical Modelling – Improved mathematical models based on existing theories are proposed, to estimate the CO2 requirement and heavy oil production during CHOP using CO2-EOR technique, and to provide an operating envelope for a wide range of operating conditions. As part of further work, the proposed models will require more refinement and validation across a broad range of operating conditions, could be adapted and modified to increase its predictive capability over time.

The miscible displacement equations provide the mathematical model for simulating the displacement of a mixture of oil and miscible fluid in underground reservoirs during the Enhance Oil Recovery(EOR) process. In this thesis, I propose a stable numerical scheme combining a mixed finite element method and space-time discontinuous Galerkin method for solving miscible displacement equations under low regularity assumption. Convergence of the discrete solution is investigated using a compactness theorem for functions that are discontinuous in space and time. Numerical experiments illustrate that the rate of convergence is improved by using a high order time stepping method. For petroleum engineers, it is essential to compute finely detailed fluid profiles in order to design efficient recovery procedure thereby increase production in the EOR process. The method I propose takes advantage of both high order time approximation and discontinuous Galerkin method in space and is capable of providing accurate numerical solutions to assist in increasing the production rate of the miscible displacement oil recovery process.

Les rejets de matières dangereuses dans l'environnement induisent souvent des pollutions accidentelles des cours d'eau qui s'étendent sur plusieurs kilomètres en aval de la source du rejet. Dans l'objectif de proposer un modèle qui prévoit l'étendue de la pollution, une maquette de cours d'eau est conçue spécifiquement en ce sens à partir d'une étude de similitude pour évaluer la dispersion de polluant en champ lointain et valider le modèle unidimensionnel adopté (Equation d'Advection-Dispersion). Les conclusions issues des études menées à petite et à grande échelle, nous ont amené à développer un modèle permettant de prédire les profils asymétriques dans la zone initiale du champ lointain. L'évaluation des performances du nouveau modèle, basé sur une Gaussienne Modifiée par une Exponentielle, montre une faible divergence des estimations par rapport aux observations. Lors de la validation à l'échelle réelle, les trois paramètres essentiels lors d'une gestion de crise (concentrations maximales, temps d'arrivée du pic et de la pollution) sont estimés respectivement avec un pourcentage d'erreur moyen de 51, 13 et 11 %, ce qui semble acceptable. Finalement, un modèle complet de dispersion est proposé pour évaluer l'étendue d'une dispersion accidentelle dans le champ lointain. Il est composé de l'EMG pour la zone initiale du champ lointain et de l'ADE pour le champ lointain établi. Le passage d'un modèle à une autre se fait à partir d'une distance comprise entre 12 et 50 fois la longueur de mélange. En conclusion, le modèle proposé est adapté à la gestion d'une situation d'urgence par la simplicité de son utilisation et le faible nombre de variables d'entrée nécessaires aux simulations.

Thesis (Doctoral)--Universität Karlsruhe, 2001. / Abstract in German. Hochschulschrift = Thèse/Mémoire. Includes bibliographical references (p. 109-133). Also available via the World Wide Web. http://www.ubka.uni-karlsruhe.de/indexer-vvv/2002/bio-geo/1

Dispersion has been shown to degrade miscibility in miscible displacements by lowering the concentration of the injected solute at the displacement fronts. Dispersion can also improve oil recovery by increasing sweep efficiency. Either way, dispersion is an important factor in understanding miscible displacement performance. Conventionally, dispersion is measured in the laboratory by fitting the solution of one-dimensional convection-dispersion equation (CDE) to the effluent concentration from a core flood. However dispersion is anisotropic and mixing occurs in both longitudinal and transverse directions. This dissertation uses the analytical solution of the two-dimensional CDE to simultaneously determine longitudinal and transverse dispersion. The two-dimensional analytical solution for an instantaneous finite volume source is used to investigate anisotropic mixing in miscible displacements. We conclude that transverse mixing becomes significant with large a concentration gradient in the transverse direction and significant local variation in flow directions owing to heterogeneity. We also utilized simulation models similar to Blackwell's (1962) experiments to determine transverse dispersion. This model coupled with the analytical solution for two-dimensional CDE for continuous injection source is used to determine longitudinal and transverse dispersivity for the flow medium. The validated model is used to investigate the effect of heterogeneity and other first contact miscible (FCM) scaling groups on dispersion. We derive the dimensionless scaling groups that affect FCM displacements and determine their impact on dispersion. Experimental design is used to determine the impact and interactions of significant scaling groups and generate a response surface function for dispersion based on the scaling groups. The level of heterogeneity is found to most significantly impact longitudinal dispersion, while transverse dispersion is most significantly impacted by the dispersion number. Finally, a mathematical procedure is developed to use the estimated dispersivities to determine a-priori the maximum grid-block size to maintain an equivalent level of dispersion between fine-scale and upscaled coarse models. Non-uniform coarsening schemes is recommended and validated for reservoir models with sets of different permeability distributions. Comparable sweep and recovery are observed when the procedure was extended to multi-contact miscible (MCM) displacements. / text

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24390号 / 理博第4889号 / 新制||理||1699(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 大木谷 耕司, 教授 並河 良典, 准教授 竹広 真一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Physical aging measurements were performed on various polymeric glasses with the overriding goal of developing a better molecular picture of the nonequilibrium glassy state. To this end, aging-induced changes in mechanical properties and in the thermodynamic state (volume and enthalpy) were assessed for two different miscible polymer blends as a function of both composition and aging temperature. This investigation considered the physical aging behavior of blends containing atactic polystyrene (a-PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as well as mixtures of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). Substantial attractive chemical interactions are characteristic of a-PS/PPO blends but are absent in PMMA/SAN blends. The distinct nature of interactions for these two blends resulted in differences in the compositional dependence of secondary relaxation intensity, segmental cooperativity which dictates glass formation kinetics, and density (prior to aging). The variation of volume relaxation rate with aging temperature and composition was interpreted based upon these characteristics for the two systems. In addition, a general relationship was uncovered which linked structural relaxation rates for amorphous polymers to their respective segmental relaxation characteristics (glass transition cooperativity or fragility), which in turn are well understood from a molecular standpoint. This work, therefore, established a basis for comprehending glassy state volume and enthalpy relaxation rates based upon molecular characteristics. Developing an understanding of the connection between the evolving thermodynamic state and mechanical property changes fared less well. The fact that the thermodynamic and mechanical properties can have very different relaxation time responses governing their changes in the nonequilibrium glassy state was clearly evident in an extensive study of the physical aging characteristics of an amorphous polyimide material. For some materials, interpretation of mechanical aging behavior was obscured by thermorheological complexity arising due to overlap of a secondary relaxation with the main chain softening dispersion. / Ph. D.

This dissertation discusses results of crystallization kinetic, morphology and scattering studies on miscible semi crystalline blends of poly(pivalolactone)/ poly(vinylidene fluoride)(pPVLIPVF₂) and poly(pivalolactone)/poly(vinylidene fluoride <i>co</i>- tetrafluoroethylene)(95-5) (PPVL/P(VF2-TFE)(95-5)) prepared by solution blending. The spherulitic growth rates of the α-phase PPVL from miscible blends with PVF₂ or P(VF₂- TFE)(95-5) were measured by polarized optical microscopy as a function of blend composition and isothermal crystallization temperature, Tx, between 160°C and 215.5°C. The PPVL weight fraction in the blends ranged from 100 to 10 wt%. Using the Lauritzen-Hoffman kinetic theory of polymer crystal growth, the equilibrium melting temperatures of the α-phase PPVL in both the PPVL/PVF₂ and the PPVL/P(VF₂-TFE)(95-5) blends have been determined, for the first time, directly from the spherulitic growth rate data. Analysis of the composition dependence of the nucleation constant, Kg suggests that the α-phase PPVL crystal/melt lateral interface free energy, Ï , in the blends decreases markedly with increasing PVF₂ or P(VF₂-TFE)(95-5) concentration. / Ph. D.

Le processus de plugging et d'abandon (P&A) des puits de pétrole et de gaz en fin de vie est essentiel pour atténuer les risques tels que la contamination de l'eau, les ruptures de pression, les émissions de gaz et les fuites d'hydrocarbures. Ce processus implique le retrait de segments de cuvelage, le nettoyage interne et externe du cuvelage pour éviter la contamination du ciment, et la mise en place de bouchons de ciment pour sceller le puits. Dans ce contexte, le nettoyage par jet, qui consiste à déplacer des fluides plus légers avec un liquide plus dense, est une technique clé. Cette technique est influencée par des facteurs tels que l'inertie, la flottabilité, la viscosité, la miscibilité et contrainte d'écoulement. Motivée par cette application industrielle, cette thèse de doctorat explore les effets des principaux paramètres de flux sur les jets miscibles flottants, en utilisant des techniques expérimentales non intrusives telles que l'imagerie haute vitesse, la vélocimétrie par images de particules tomographique résolue dans le temps, la fluorescence induite par laser planaire et la vélocimétrie Doppler à ultrasons. Nos travaux examinent notamment comment la vitesse d'injection du jet, le diamètre de la buse, la différence de densité, le rapport de viscosité et la contrainte d'écoulement affectent la dynamique du jet. Plus précisément, nous analysons des caractéristiques telles que la longueur laminaire, la longueur de pénétration, le rayon du jet, le profil de vitesse, l'énergie dissipée, l'indice de mélange et l'énergie cinétique turbulente pour caractériser le comportement des jets flottants. Les résultats sont présentés en fonction de nombres adimensionnels, y compris les nombres de Reynolds (Re), Froude (F r), Archimède (Ar) et Bingham (BN ), ainsi que le rapport de viscosité (m). Pour les jets Newtoniens verticaux isovisqueux, nous étudions le flux sur une gamme de Re, F r, et Ar pour classifier les régimes de flux, basés sur l'absence ou la présence de longueur laminaire, en jets semi-turbulents et totalement turbulents. Nous quantifions également les transitions entre ces régimes (Re critique) et développons des corrélations prédictives pour les caractéristiques du jet. Nous employons ensuite des techniques d'apprentissage automatique supervisé, y compris les forêts aléatoires, pour améliorer les prédictions des caractéristiques du jet à travers divers Re et Ar, surpassant les méthodes traditionnelles. Nous étudions ensuite les effets de m sur les comportements de flux de jet flottant, identifiant trois régimes de flux distincts (méduse, entonnoir et cône) et quantifiant comment l'augmentation de m influence l'instabilité ou la stabilité selon le régime de flux. En considérant les fluides ambiants à contrainte d'écoulement, pour les jets neutres flottants, nous identifions quatre régimes de flux de jet, y compris les motifs de mélange, de champignon, de doigts et de fracture, par rapport à Re et BN , et démontrons comment l'augmentation du rapport de la contrainte d'écoulement à la contrainte d'inertie du jet (BN /Re) régit la transition entre ces régimes. Enfin, en élargissant le champ de notre travail, nous explorons l'impact de l'épaisseur de la couche de fluide ambiant et de la contrainte d'écoulement sur l'efficacité du nettoyage d'un jet turbulent frappant des fluides Newtoniens et à contrainte d'écoulement, révélant que la contrainte d'écoulement modifie les dynamiques de nettoyage et l'entraînement de l'air. / The plug and abandonment (P&A) of oil and gas wells at their lifecycle end is crucial to mitigate risks, such as water contamination, pressure breakdowns, gas emissions, and hydrocarbon leaks. The P&A process involves removing casing segments, cleaning both interior and exterior of the casing to prevent cement contamination, and placing cement plugs to seal the well. In this context, jet cleaning, which involves displacing lighter fluids with a denser liquid, is a key cleaning technique, and it is influenced by inertia, buoyancy, viscosity, miscibility, and yield stress properties. Motivated by this industrial application, the current Ph.D. thesis investigates the effects of the key flow parameters on miscible buoyant jets, using non-intrusive experimental techniques, including high-speed imaging, time-resolved tomographic particle image velocimetry, planar laser-induced fluorescence, and ultrasound Doppler velocimetry. Our work explores, in particular, how the jet injection velocity, nozzle diameter, density difference, viscosity ratio, and yield stress affect the jet dynamics. Specifically, the jet flow characteristics, such as the laminar length, penetration length, jet radius, velocity profile, dissipated energy, mixing index, and turbulent kinetic energy are analyzed to characterize buoyant jet behavior. The results are accordingly presented versus the dimensionless numbers, including the Reynolds (Re), Froude (F r), Archimedes (Ar), and Bingham (BN ) numbers, as well as the viscosity ratio (m). For iso-viscous Newtonian vertical buoyant jets, we study the flow across a range of Re, F r, and Ar, to classify the flow regimes, based on the absence or presence of the laminar length, into semi-turbulent and fully-turbulent jets. We also quantify the transitions between these regimes (critical Re), and develop predictive correlations for the jet characteristics. We subsequently employ supervised machine learning techniques, including random forests, to enhance the jet characteristic predictions, across various Re and Ar, outperforming traditional methods. We then investigate the effects of m on buoyant jet flow behaviors, identifying three distinct flow regimes (jellyfish, funnel, and cone), and quantifying how increasing m influences instability/stability depending on the flow regime. Considering yield stress ambient fluids, for neutrally buoyant jets, we identify four jet flow regimes, including mixing, mushroom, fingering, and fracturing patterns, versus Re and BN and demonstrate how increasing the ratio of the yield stress to jet inertia stress (BN /Re), governs the transition among these regimes. Finally, expanding the scope of our work, we explore the impact of the ambient fluid layer thickness and yield stress on the cleaning efficacy of a turbulent jet impinging on Newtonian and yield stress fluids, revealing that the yield stress modifies cleaning dynamics and air entrainment.

No estudo da dinâmica de solutos num meio poroso é de suma importância o conhecimento das propriedades do meio e dos líquidos percolantes, bem como de fatores externos. Um fator externo relevante é a temperatura e, nesse sentido, objetivou-se com o presente trabalho a determinação de parâmetros de transporte dos íons potássio e nitrato para diferentes valores de temperatura em experimentos de deslocamento miscível. Os parâmetros avaliados foram o fator de retardamento (R), o coeficiente de difusão/dispersão (D) e a dispersividade (&#955;) e as temperaturas utilizadas foram a ambiente (25&#176;C a 28&#176;C), 40&#176;C e 50&#176;C. Os sais utilizados foram nitrato de potássio e cloreto de potássio, preparados em uma solução composta de 50ppm de nitrato e 2000ppm de potássio e o meio poroso um Latossolo Vermelho Amarelo, textura média. Os resultados obtidos permitiram concluir que a temperatura apresentou influência na velocidade da solução no meio poroso e no coeficiente de dispersão. / In the study of solute dynamics in porous media, it is of extreme importance the knowledge of the medium and transporting liquid properties as well as of external factors as temperature. In this sense, the objective of this work was the determination of parameters for potassium and nitrate ions under different temperatures in miscible displacement experiments, in a sandy loam Oxisol. The evaluated parameters were retardation factor (R) difusion/dispersion coefficient (D) and dispersivity (&#955;), whereas the used temperatures were the prevailing temperature (25&#176;C to 28&#176;C), 40&#176;C and 50&#176;C. The used salts were potassium nitrate and potassium chloride, prepared in a composed solution of 50 ppm of nitrate and 2000 ppm of potassium. From the results, it could be concluded that the temperature showed high influence on soil solution velocity and dispersion coefficient