Academic literature on the topic 'Inversion de pression'

Résumé La concentration de nitrate dans les 25 principales rivières bretonnes est, dans 90 % des cas, corrélée positivement au débit. Les caractéristiques hydrogéologiques des bassins versants jouent sur les termes de cette corrélation; ainsi, un taux d’écoulement superficiel important (caractéristique des bassins versants peu perméables) renforce cette corrélation et diminue le décalage temporel entre les pointes de crue et de concentration de nitrate. L’évolution pluriannuelle des concentrations de nitrate dans les rivières bretonnes est caractérisée par un quadruplement durant les trente dernières années. Par contre, depuis le milieu des années 90, on observe sur 80 % des rivières une tendance à la décroissance, indépendamment des évolutions pluriannuelles des débits. Le taux annuel de décroissance est d’autant plus fort que le bassin versant présente une part importante d’écoulements superficiels, et a donc une moins grande inertie hydrogéologique. Étant donné que les temps de réaction des bassins versants sont relativement courts (2‑10 ans), il se peut que l’on commence à constater l’effet sur les eaux superficielles d’une inversion de tendance concernant la pression agricole (baisse des fumures organiques et minérales azotées depuis le début des années 90). Ces tendances restent à confirmer et ne permettent pas encore d’atteindre, dans de nombreuses rivières, des concentrations de nitrate inférieures au seuil à partir duquel se produisent des proliférations macroalgales en zone côtière, ou de permettre sans problème la production d’eaux destinées à la consommation humaine.

<p>A Análise de Testes de Poços é um ramo da Engenharia de Reservatórios no qual<br />empregamos dados de pressão de poço a partir de testes de produção/injeção de fluido em conjunto com modelos físico-matemáticos para caracterizar o sistema poço-reservatório, usando problemas inversos. Nessas situações, aplicamos amplamente soluções analíticas e semianalíticas do modelo físico-matemático que descreve o fluxo. Nesse contexto, o objetivo do presente estudo é 1) realizar uma revisão bibliográfica sobre algumas das soluções analíticas clássicas para determinação da pressão no poço produtor e 2) implementar os códigos numéricos para a criação de uma biblioteca computacional, proporcionando as soluções analíticas voltadas para a determinação da pressão em poços produtores de petróleo. Os sistemas poço-reservatório estudados possuem um poço vertical e levam em consideração os efeitos de condições de contorno, a estocagem na coluna de produção do poço, dano à formação, períodos de fluxo e estática, bem como a presença de fraturas naturais. Obtivemos as soluções analíticas usando a transformada de Laplace e uma inversão numérica, utilizando o algoritmo Stehfest, para calcular a variação de pressão ao longo do tempo.</p><p><br /><strong>Palavras-chave</strong>: Soluções Analíticas, Transformada de Laplace Inversa, Tranformada de Laplace, Algoritmo de Stehfest, Análise de Teste de Poço.</p><p>===================================================================</p><p>Well Testing Analysis is a branch of Reservoir Engineering, in which we<br />employ well pressure data from production tests/fluid injection in conjunction with physical-mathematical models to characterize the well-reservoir system, using inverse problems. In these situations, we widely used analytical and semi-analytical solutions of the physical-mathematical model that describes the flow. In this context, the objective of this work is to 1) carry out a bibliographic review on some of the classic analytical solutions for determining the pressure in the producing well and 2) implement the numerical codes for the creation of a computational library, providing the analytical solutions aimed at determining pressure in oil-producing wells. The well-reservoir systems with a vertical well take into account the boundary effects, wellbore storage, formation damage, drawdown and buildup test analysis, and the presence of natural fractures. We obtain the analytical solutions using the Laplace transform and a numerical inversion, using the Stehfest algorithm, to calculate the pressure variation in the time domain.</p><p><br /><strong>Key words</strong>: Analytical Solutions, Inverve Laplace Transform, Laplace Transform, Stehfest Algorithm, Well Testing Analysis.</p>

In this work, a polyethylene terephthalate (PET) nonwoven support was prepared by wet-laid and hot-press technology and used as support for separation membranes. The properties of the PET nonwoven support were studied to determine the effect of hot-pressing parameters and PET fiber ratio, and were optimized by response surface methodology. Result showed that the PET nonwoven support with 62% low melting point PET (LPET-180) fibers obtained satisfactory properties and structure after hot pressing at 220 °C under the pressure of 9 MPa for 20 s. The response surface analysis indicated that the temperature and time of hot pressing and the fiber ratio were the most important factors affecting the strength and air permeability of the PET nonwoven support. After hot pressing, the PET nonwoven support exhibited interconnected structure, small pore size, low porosity, and high strength. Then phase inversion technique was applied to prepare a polysulfone (PSF) layer on the PET nonwoven support and an ultra-thin polyamide (PA) active layer was prepared by interfacial polymerization on the PSF layer. The practicality of PET nonwoven support was verified by testing the pure water flux and retention of the PA composite membrane and the structural change of the PA composite membrane before and after use. The results proved the feasibility and remarkable application prospects of hot-pressed wet-laid PET nonwoven support as support for separation membranes.

Abstract This study considers the rheological and interfacial effects on the phase morphology of the rubber/plastic blends during molten-state mixing, cold pressing, and compression molding. We utilized a specially designed tool to take a sample from the mixer and quickly cool it with little chance for coalescence. The work of this report is mainly concerned with soft rubbery compositions, which contain large concentrations of elastomeric phases. The morphologies of rubber/plastic blends having low concentrations of plastic or rubber can be explained by the understanding gained from work previously reported by others. The viscosity-matched and polarity-matched rubber/plastic blend systems give the finer states of dispersion, especially during the early stages of mixing. At intermediate concentrations of rubber, (e.g., 60 vol. %) co-continuous and laminar structures are frequently formed. The determinants of the concentration where the phase inversion occurs and the determinants of phase-domain dimensions near this phase-inversion concentration (e.g., a thickness of a highly shaped structure) are complex and can only be rationalized qualitatively. However, we were able to quantitatively relate phase-morphological dimensions to interfacial tension, rheology, and the observed type of morphology. When the hot batch is cold pressed, then a striated or laminar phase morphology is formed. Even very small particles deform greatly if the interfacial tension is low. Higher viscosities in the dispersed phase give rise to lesser deformations during cold pressing. During compression molding, the laminar structure transforms itself into a random co-continuous structure of vastly increased textural dimensions. This coarsening is greatest when polarities are most divergent and when the viscosities of the polymers are lowest.

Palygorskite has remarkable rheological properties and was used to increase the stability and viscosity of aqueous suspensions. The effects of different physical and chemical processing methods on the apparent viscosity and plastic viscosity of the palygorskite suspensions such as pressing, ultrasound scattering, acidification, and chemical additives have been released. The pressing and ultrasound scattering indicated that the dispersed state of palygorskite could be increased effectively after treatment, and the apparent viscosity of treated-palygorskite samples increased almost 2-3 times compared to that of before. The viscosity of the acid-treated palygorskite suspension was not increased. The viscosity increased with the content of bentonite in the mixture of bentonite and palygorskite in fresh water. It seemed to be not worthy to add a certain amount of bentonite to palygorskite in order to enhance viscosity and vice versa. Chemical additives appeared to have good effects on the rheological behavior of palygorskite suspension. Magnesium oxide revealed great contribution to viscosity enhancement. The main mechanism was the electrostatic attractive interaction between magnesium oxide particles with positive charges and the palygorskite rods with negative charges. This interacted force has an impact on the structural inversion of palygorskite rods and even caused the reinforcing of flocculation.

Copolymers of 3-hydroxyvalerate (HV) and 3-hydroxyhexanoate (HHx) membranes are a new family of biomaterials for tissue engineering applications. The object of this study is to investigate the behavior of rat tooth germ cells on various 3-hydroxyl-butyrate-co-3-hydroxy-hexanoate (PHBHHx) membranes. In this study, PHBHHx membranes from three thin-film processes were used. PHBHHx membranes with different surface morphologies were prepared by phase inversion, electrospinning, and hot pressing. The morphologies of the PHBHHx membranes were investigated by scanning electron microscopy (SEM). Tooth germ cells were isolated from four-day-old Wistar rats. The cellular adhesion, proliferation and viability were determined by SEM, BrdU (5-bromo-2-deoxyuridine) and MTT (3-[4, 5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; Thiazolyl blue) assay. In addition, the adherent behavior of tooth germ cells on various surface structures of PHBHHx was observed under a fluorescence microscope after staining of the cytoskeletal filamentous actin of the cells. It was found that cell compatibility of the PHBHHx membranes made from the phase inversion method (p-PHBHHx) was better than that of the other PHBHHx membranes. The results also revealed that tooth germ cells cultured on the PHBHHx membranes with porous surface structure were well spread relative to those on the fibrous structure of PHBHHx membranes. Therefore, PHBHHx membranes with a porous surface structure can encourage either cell adhesion or cell proliferation. PHBHHx membranes with a porous morphology satisfy biomaterial requirements for a scaffold for tooth regeneration.

Polycrystalline ZnO was sintered with 5 mol.% Ga2O3 at 1350°C for lhour in air. Samples for transmission electron microscopy (TEM) were prepared by cold pressing, grinding, dimpling and Argon ion-milling.ZnO crystallizes in the hexagonal wurtzite structure. Bright field and dark field images reveal lamellar defect structures which are not observed in undoped ZnO. Electron diffraction shows that the lamellar regions consist of heavily twinned ZnO. The twin boundaries (TB) of both twin variants are parallel to lattice planes of type { }. Lattice images along reveal narrow planar twin boundaries as well as a diffuse image contrast within the twin lamellae (Fig. la). to characterize the nature of the boundaries we recorded dark field images of the twinned regions using reflections of type ±{0002}. in combination with microdiffraction it can be shown that the diffuse boundaries are inversion domain boundaries (IDB) which alternate with the sharp TB. This microstructure is related to the polarity of ZnO.

Equal-channel angular pressing (ECAP) is known to induce significant grain refinement and formation of tangled dislocations within the grains. These are induced to evolve to form low-angle boundaries (i.e., cell boundaries) and eventually high-angle boundaries (i.e., grain boundaries). On the other hand, the precipitation sequence of age hardening aluminum alloys can be significantly affected by pre-straining and severe plastic deformation. Thus, ECAP is expected to influence the T6 response of aluminum alloys. In this study, a complex Al-Cu-Mg-Li-Ag-Zr-Sc alloy was subjected to ECAP following different straining paths. The alloy was ECAP at 460 K via route A, C, and by forward-backward route A (FB-route A) up to four passes. That is, ECAP was carried out imposing billet rotation between passes (route A), billet rotation by +90° between passes (route C), and billet rotation by +90° and inversion upside down between passes (FB-route A). The alloy was also aged at 460 K for different durations after ECAP. TEM microstructure inspections showed a marked influence of the different shearing deformations induced by ECAP on the alloy aging response. The precipitation kinetics of the different hardening secondary phases were affected by shearing deformation and tangled dislocations. In particular, the T1-Al2CuLi phase was the one that mostly showed a precipitation sequence speed up induced by the tangled dislocations formed during ECAP. The T1 phase was found to grow with aging time according to the Lifshitz-Slyozov-Wagner low-power regime.

Cette thèse est consacrée à la conception d'un système de mesure indirecte pour l'estimation quantitative de paramètres de combustion pertinents en termes de diagnostics et de contrôle moteur, fondé sur l'observation d'une grandeur aisément accessible, le signal d'ionisation. Nous avons envisagé une approche au sens des problèmes inverses. Il s'agit de construire un modèle paramétrique du signal d'ionisation au moyen des équations de la physique puis d'estimer les paramètres par inversion du modèle dans une boucle d'optimisation. L'extrême complexité des phénomènes participant vraisemblablement à la construction de ce signal ne nous a pas permis d'aboutir et nous nous sommes orientés vers une approche plus expérimentale. Nous avons mené une analyse statistique aveugle des données fournies par RENAULT dans le but d'expliciter une relation entre le signal d'ionisation et les grandeurs à estimer. L'étude statistique de données évoluant dans un espace de grande dimension étant notoirement maladroite, différentes méthodes classiques de réduction de la dimension apparente des données telles que l'Analyse en Composantes Principales, Projection Pursuit, etc. Ont été utilisées avec profit. Nous avons par ailleurs proposé une extension de cette dernière méthode en montrant l'utilité de critères issus de la théorie de l'information tels que l'information mutuelle ou la mesure de dépendance de Hellinger, pour la sélection de projections intéressantes. Nous avons aussi pu profitablement diminuer la dimension des données étudiées en recherchant un ensemble réduit de variables intermédiaires susceptibles de retenir une information relative à la grandeur d'intérêt. Ces analyses nous ont ensuite permis de proposer différents estimateurs de l'angle de pression de chambre maximale dont la précision et la stabilité ont été étudiées sur un sous ensemble des données disponibles correspondant à un domaine assez large de points de fonctionnement du moteur
The work described in this thesis investigates the possibility of constructing an indirect measurement algorithm of relevant combustion parameters based on ionization signal processing. Indeed, automobile manufacturers are in need of low cost combustion diagnoses to enhance engine control. Because of the extreme complexity of the physical phenomena in which the ionization signal originates, the traditional model-based approach appeared unrealistic and did not bring about conclusive results. We hence turned to performing a blind statistical analysis of experimental data acquired on a test engine. The analysis of high dimensional data being notoriously awkward, it is necessary to first reduce the apparent dimension of the signal data, keeping in mind the necessity of preserving the information useful in terms of our estimation problem. The usual techniques such as Principal Component Analysis, Projection Pursuit, etc. Are used to form and detect relevant variables. Further, a procedure for high dimensional data analysis derived as an extension of Exploratory Projection Pursuit, is suggested and shown to be a profitable tool. With this method, we seek interesting projections of high dimensional data by optimizing probabilistic measures of dependence such as Mutual Information, Hellinger divergence, etc. Finally, results are presented that demonstrate the quality and the stability of the low complexity in-cylinder peak pressure position estimators we derived, for a wide range of engine states

Du fait de l’épuisement des réserves de pétrole, l’exploration et la production sont réalisées dans des environnements de plus en plus complexes. Faire de l’imagerie sismique sous le sel allochtone (par exemple dômes de sel) demeure une tâche difficile à cause du fait contraste de vitesse dentre le sel et les sédiments voisins et les structures très complexes produites par les déplacements de sel. Les nappes de sel allochtone couvrent de nombreuses régions potentiellement productives dans l’offshore profond du Golfe du Mexique. Forer la base du sel est une tâche extrêmement difficile en raison des pressions de pore fortement variables que l’on recontre dans les sédiments sous le sel. Des méthodes sismiques pour estimer la vitesse des ondes sismiques peuvent être employées en même temps que des formules empiriques pour prévoir la pression de pore. Cependant, il est souvent impossible de mesures précises depuis la surface, et nous avons donc employé des données VSP (Vertical Seismic Profile) “walk-away” cela implique d’effectuer plusieurs tirs sismique à diverses distances du forage (géneralement avec un dispositif de canons á air) tout en enregistrement les vitesses mesurees par des geophones placés à des profondeurs appropriées dans le forage. Avant cette thèse, les données étaient traitées en utilisant l’information d’amplitude en fonction de l’angle dans un simple approximation 1D ou en utilisant l’information de temps de parcours (également avec une approximation 1D). Dans cette thèse, j’ai effectué une inversion 2D de forme d’onde pour résoudre le problème d’estimation des vitesses. Cela a l’avantage d’inverser simultanément l’ensemble des données (comprenant les ondes transmises, les ondes refléchies et les ondes converties) et la méthode inclut l’information de temps de parcours et d’amplitude. L’inversion a été exécute avec des méthodes locales d’inversion du fait de la taille du problème inverse et de la difficulté du problème direct. Les problèmes liés aux grandes variations de le sensibilité inhérents à l’acquisition de données, ont conduit à un examen de la méthode de Gauss- Newton et à des matrices, de préconditionnement possibles pour la méthode du gradient conjugué. En raison de la nature mal contrainte du problème inverse, une régularisation a été appliquée avec une méthode de préconditionnement innovatrice. La méthodologie a été appliquée à des données réelles et la pression de pore a été prédite en utilisant l’équation bien établie de Eaton. En outre, les structures sous le sel ont été déterminées, confirment ainsi l’efficacité de cette technique
Depletion of the earth’s hydrocarbon reserves has led to exploration and production in increasingly complex environments. Imaging beneath allochthonous salt (e. G. Salt domes) remains a challenging task for seismic techniques due to the large velocity contrast of the salt with neighbouring sediments and the very complex structures generated by salt movement. Extensive allochthonous salt sheets cover many potentially productive regions in the deep-water Gulf of Mexico. Drilling through the base of salt is an extremely challenging task due to widely varying pore-pressure found in the sediments beneath. Seismic methods to estimate the seismic velocity can be used in conjunction with empirical formula to predict the pore pressure. However, accurate measurements are often not possible from surface reflection seismic data, so walk-away Vertical Seismic Profile (VSP) data has been used. This involves repeatedly firing a seismic source at various distances from the borehole (usually an airgun array) while recording the velocities measured by geophones in the borehole placed at appropriate depths near the base of the salt. Before this thesis, the data had been processed using the amplitude versus angle information in a simple one-dimension approximation or using travel time information (also using a 1D assumption). In this thesis, I have used 2D full waveform inversion to tackle the problem of velocity estimation. This has the advantage of simultaneously inverting the whole dataset (including transmitted waves, reflected waves, converted waves) and the method includes traveltime and amplitude information. The inversion was performed using local inversion methods due to the size of the inverse problem and the cost of the forward problem. Concerns over large sensitivity variations, that are inherent in the data acquisition, have lead to an examination of the Gauss-Newton method and possible preconditioning matrices for the conjugate gradient method. Due to the poorly constrained nature of the inverse problem, a smoothness constraint has been applied with an innovative preconditioning method. The methodology has been applied to real data and the pore pressure has been predicted using the well established Eaton equation. In addition, the sub-salt structure was recovered, further demonstrating the value of this technique

Les garnitures mécaniques sont utilisées dans de multiples applications pour réaliser l'étanchéité autour d'arbres en rotation. Ces composants peuvent fonctionner efficacement pendant plusieurs années en conditions stables, mais leur durée de vie est significativement réduite lorsque les conditions varient. L'objectif de ce travail de recherche est de développer et d’utiliser un banc d'essais et code de calcul pour étudier l'impact de pulsations de pression, d’inversions de pression et du chargement dynamique résultant sur les performances de garnitures mécaniques ayant des faces mésalignées et présentant des défauts de planéité.Le solveur fluide d'un modèle numérique de garnitures mécaniques a été étendu aux conditions transitoires. Un module résolvant la dynamique des forces et des moments a été ajouté afin de prédire le déplacement axial et les déplacements angulaires de la face montée de manière flexible. Afin de caractériser les performances de garnitures, un banc d'essais générant des pulses de pression a été instrumenté et des méthodes de mesure de perte de volume d'huile et d'entrée d'eau mises en place.Des garnitures mécaniques à faces parallèles puis mésalignées, fonctionnant sous pulsations et inversions de pression, ont été testées expérimentalement et simulées. Seules de très faibles augmentations d'eau dans l'huile ont été observées, sans augmentation au cours du temps, et sans fuite d'huile mesurable. Les faibles valeurs d'entrées d'eau sont dues à la faible épaisseur de film et à la courte durée des inversions de pression. Une garniture mécanique expérimentale à fort défaut de planéité a aussi été testée. Contrairement aux autres paramètres, le défaut de planéité semble augmenter significativement la fuite et promouvoir les entrées d'eau et pourrait ainsi être à l'origine de certaines défaillances
Face seals are mechanical devices used to seal rotating shafts in numerous applications. While they can operate efficiently under steady conditions for years, they tend to fail prematurely when operating in severe, or rapidly varying conditions. The focus of this research work is the development and use of an experimental and a numerical method to investigate the impact of pressure pulses, pressure inversions and induced dynamic loading on the performance of mechanical face seals exhibiting face misalignment and waviness.The fluid solver of a state-of-the art face seal numerical model was extended to transient conditions and a module solving the dynamics for the axial and angular degrees of freedom of the flexibly-mounted stator added. A system-level experimental setup generating pressure pulses was instrumented and methods to characterise face seal performance in terms of oil volume loss and ingression of water outer-fluid selected and implemented.Face seals, with flat and misaligned faces, operating under pressure pulses and pressure inversions were experimentally tested and simulated. They show only slight increase of water in the oil, no increase over time, and no measurable oil leakage. The low water ingression is due to low film thickness combined with the short duration of pressure inversions. An exploratory face seal of high waviness was also experimentally tested. Contrary to the other parameters, the waviness appears to significantly increase the leakage and promote water ingression and could thus be at the origin of some seal failures

Dans les puits de production d’eau, de pétrole, de gaz et de chaleur géothermique, ou dans les puits d’accès à un stockage d’hydrocarbures, il est précieux de connaître la perméabilité de la formation ou de sa couverture en fonction de la profondeur, soit pour améliorer le modèle de réservoir, soit pour choisir les zones dans lesquelles procéder à des opérations spéciales.On propose une technique qui consiste à balayer la hauteur du découvert par une interface entre deux liquides de viscosités très contrastées. Le débit total qui pénètre la formation à chaque instant est ainsi une fonction de la position de l’interface et de l’historique des pressions dans le puits. On doit alors résoudre un problème inverse : rechercher la perméabilité fonction de la profondeur à partir de l’historique des débits dans le temps. Dans la pratique, le puits est équipé d’un tube central. Le balayage est effectué par injection d’un liquide à pression d’entrée constante dans le tube central et soutirage d’un autre liquide par l’espace annulaire. On mesure les débits d’injection et de soutirage dont la différence est le débit qui entre dans la formation.Pour valider et améliorer cette technique, on a d’abord utilisé une maquette simulant un découvert multi-couches disponible au LMS. On a exploité aussi des essais en place réalisés dans la couverture peu perméable d’un stockage souterrain de gaz. Dans ces essais, un liquide visqueux placé dans le découvert était déplacé par un liquide moins visqueux (méthode dite « opening »). Les couches plus perméables étaient correctement identifiées (Manivannan et al. 2017), mais une estimation quantitative était un défi en raison des phénomènes transitoires qui affectent le voisinage immédiat des puits. De plus, le rayon investigué dans le massif était petit.La thèse a relevé ces défis en proposant un essai légèrement différent et une nouvelle technique d’interprétation. Les essais avec une maquette modifiée ont montré la supériorité d’une méthode « closing » dans laquelle le puits est d’abord rempli du liquide le moins visqueux. On ménage une période de stabilisation avant l’injection du liquide visqueux pour réduire les effets transitoires ; elle permet aussi d’estimer la perméabilité moyenne et l’influence de la zone endommagée à la paroi (le « skin »).Puis on conduit l’essai proprement dit. L’historique des débits mesurés en tête de puits constitue le profil d’injection dont on déduit le profil de perméabilité.. Cette estimation suppose un écoulement monophasique dans chaque couche et la même « skin » pour toute la formation. Les incertitudes principales portent sur les pressions de formation et les variations possibles du « skin ». Elles sont estimées au moyen d’un calcul analytique. On a vérifié sur la maquette que les profils de perméabilité estimés présentent une bonne concordance avec les perméabilités mesurées avant les essais.On a réalisé un essai sur un sondage de 1750 m de long atteignant une couche de sel dont on a correctement estimé la perméabilité moyenne pendant la période de stabilisation. Toutefois elle était si faible (4.0E-21 m²) que l’utilisation de deux fluides n’a pas permis de faire une différence entre les diverses parties du puits
In wells producing water, oil, gas or geothermal energy, or in access wells to hydrocarbon storage, it is critical to evaluate the permeability of the formation as a function of depth, to improve the reservoir model, and also to identify the zones where additional investigation or special completions are especially useful.A new technique is proposed, consisting of scanning the open hole (uncased section of the wellbore) with an interface between two fluids with a large viscosity contrast. The injection rate into the formation depends on interface location and well pressure history. An inverse problem should be solved: estimate permeability as a function of depth from the evolution of flow rates with time. The wells are usually equipped with a central tube. The scanning is done by injecting a liquid in the central tube at constant wellhead pressure. Injection and withdrawal rates are measured at the wellhead; the difference between these two rates is the formation injection rate.To validate and improve this technique, we used a laboratory model mimicking a multi-layer formation, already available at LMS. We also made use of in-situ tests performed on an ultra-low permeable cap rock above an underground gas storage reservoir. In these tests, a viscous fluid contained in the open hole was displaced by a less-viscous fluid (a method called opening WTLog). The more permeable layers were correctly identified (Manivannan et al. 2017), but a quantitative estimation was challenging due to transient phenomena in the vicinity of the wellbore (near-wellbore zone). In addition, the investigation radius was small.These challenges are addressed by proposing a slightly modified test procedure and a new interpretation workflow. Laboratory tests with a modified test setup showed the advantages of the ‘closing’ method in which the well is filled with a less-viscous fluid at the start of the test. We also added a stabilization period before the injection of viscous fluid to minimize the transient effects; this period is also used to estimate the average permeability of the open hole and the effect of near-wellbore damage (skin).Then the test proper is performed (closing WTLog). The injection profile of the less-viscous fluid is computed from the wellhead flow rate history. A permeability profile is estimated from the injection profile. The permeability estimation considers a monophasic flow in each layer and the same skin value for all the formation layers. Major uncertainties in the permeability estimates are caused by formation pressures and heterogeneities in skin values; they are estimated using an analytical formula. We have verified on the laboratory setup that the estimated permeability profiles are well correlated to the permeabilities measured before the tests.An attempt was made to perform a WTLog in a 1750-m long wellbore opening in a salt formation. The first phase was successful and the average permeability was correctly assessed. However, this permeability was so small (4.0E-21 m² or 4 nD) that the gauges and the flowmeters were not accurate enough to allow a clear distinction between the permeabilities of the various parts of the open hole

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The study of the best utilization of high intensity discharge lamps deals with the great global concern with energy efficiency. Electronic ballasts are the current devices that can make the good use of high luminous efficacy and the long useful life of these lamps. This work aims to develop an electronic ballast to supply high intensity discharge lamps. In order to avoid the acoustic resonance phenomenon occurrence, the lamp is supplied with low frequency square waveform. Power control and voltage inversion stage in the lamp are developed by the biflyback inverter topology. The analysis and design of this topology were performed, as well as the development of resonant inversion methodology of the lamp voltage. It is proposed one study, qualitative and quantitative, of active converters to provide the power factor correction, and their integration with the biflyback inverter topology. Buck biflyback inverter topology is chosen to the implementation of practical experiments, in order to validate the present work. The converter modeling, considering the lamp dynamic, such as the stability analysis and theoretical control strategy of current and lamp power are presented. Experimental results show that the proposed electronic ballast has the follow characteristics: high power factor (0.97), low input current harmonic distortion, high efficiency (88%) and not visible occurrence of acoustic resonance phenomenon.
O estudo do melhor aproveitamento das características das lâmpadas de descarga em alta pressão vem ao encontro da grande preocupação mundial com a eficientização energética. Reatores eletrônicos são os dispositivos atuais que melhor aproveitam a alta eficácia luminosa e longa vida útil dessas lâmpadas. Este trabalho visa o desenvolvimento de um reator eletrônico para a alimentação de lâmpadas de descarga em alta pressão. De modo a não excitar a ocorrência do fenômeno de ressonância acústica, a alimentação da lâmpada é realizada através de forma de onda de corrente quadrada em baixa frequência. Os estágios de controle de potência e inversão da tensão na lâmpada são realizados pela topologia biflyback inversora. A análise e projeto desta topologia foram realizados, assim como o desenvolvimento de uma metodologia de inversão ressonante da tensão da lâmpada. É proposto um estudo, qualitativo e quantitativo, dos conversores ativos para correção do fator de potência, e a integração destes, com a topologia biflyback inversora. A topologia buck biflyback inversora foi escolhida para a realização de experimentos práticos para a validação do trabalho. A modelagem do conversor, considerando a dinâmica de uma lâmpada de descarga em alta pressão de sódio foi realizada. Assim como a análise da estabilidade e estratégias de controle da corrente e da potência na lâmpada. Os resultados experimentais comprovam que o reator eletrônico proposto apresenta as características desejadas de: alto fator de potência (0,97), atendimento da norma IEC61000-3-2 para o nível das harmônicas da corrente de entrada, elevado rendimento (88%) e não excitação visível do fenômeno de ressonância acústica.

A maioria dos poços de petróleo offshore explorados no Brasil utilizam a técnica de elevação artificial de petróleo conhecida como gas-lift. Mais importante, há previsão de uso intensivo dessa técnica nos poços do pré-sal, sob pressões extremas e condições operacionais ainda não compreendidas completamente. O efeito de injetar gás em um escoamento em tubo vertical é o decréscimo do componente gravitacional do gradiente de pressão total. Por outro lado, os óleos pesados (10 < ºAPI < 19) são viscosos e difíceis de escoar. Em certas ocasiões, este tipo de petróleo não é extraído pela falta de tecnologia viável ou pelo alto custo do processo de produção. Alguns estudos recentes indicam que, para óleos ultra viscosos, o cisalhamento viscoso (componente \"friccional\") seria significativo no computo do gradiente de pressão total. Percebe-se, portanto, que deve existir, para cada condição de escoamento específica, um grau API ou uma viscosidade limite do fluido, acima do qual a técnica gas-lift torna-se ineficiente, quando não inútil. Dessa forma, o estudo do uso da água como fluido coadjuvante para a elevação artificial torna-se válido para óleos viscosos e pode ser indicado para melhorar a produtividade e reduzir a potência requerida de bombeamento. Outra questão é a possibilidade do escoamento trifásico gás-óleo-água ser promissor na redução do gradiente de pressão total. Dessa forma, para a prospecção dessa problemática e a avaliação dessas questões foram realizados testes em laboratório, utilizando misturas de óleos de diversas viscosidades (100 cP, 220 cP e 325 cP), onde foram quantificados os ganhos oferecidos pela injeção de gás, no caso ar, e de água em termos de fatores de redução de gradiente de pressão e fatores de desempenho. Além disso, com o intuito de melhor compreender a fenomenologia de escoamentos trifásicos, foram realizadas análises quanto ao deslizamento entre as fases e a aplicabilidade do modelo de deslizamento. Por fim, através de uma modelagem, foi verificado o efeito do deslizamento entre as fases na queda de pressão total em tubulações de elevado comprimento.
Most of the offshore oil wells operated in Brazil use the artificial lifting technique known as gas-lift. More importantly, an intensive use of this technique in the pre-salt wells under extreme pressures and operating conditions not yet completely understood is planned. The effect of injecting gas into the flow in a vertical pipe is the decrease of the gravitational component of the total pressure gradient. On the other hand, the heavy oils (10 < ºAPI < 19) are viscous and difficult to flow. In some occasions, this type of oil is not extracted by the lack of viable technology or by the high cost of the production process. Some recent studies indicated that for ultra-viscous oils, viscous shear stress (\"frictional\" component) would be significant in the total pressure gradient. Therefore, there must be an API degree or a fluid viscosity limit for each specific flow condition above which the \"gas-lift\" technique becomes inefficient. Thus, the study of water used as method of artificial lift becomes valid for viscous oils and can be indicated to improve productivity and reduce the pumping power required. Another issue is that the gas-oil-water three-phase flow can be advantageous in reducing the overall pressure gradient. Thus, for prospecting of this problems and the evaluation of these issues, tests were performed in laboratory using mixtures of oils with different viscosities (100 cP, 220 cP e 325 cP), at which the gains offered by gas (air) and water injection were quantified by pressure gradient reduction factors and performance factors. Furthermore, in order to better understand the phenomenology of three phase flows, analyzes were performed about the slip between the phases and the applicability of the drift flux model. Finally, the effect of slippage between the phases in the total pressure drop in long pipes was checked through modeling.

Cette étude est motivée par le manque de mesures de paramètres d'anisotropie à l'échelle de la sismique de puits. Le but est de déterminer localement ces paramètres à partir de données de puits en trois composantes du type walkaway. On s'est intéressé pour cela à des milieux TI d'axe de symétrie contenu dans un plan vertical. Les données sont constituées par les lenteurs apparentes verticales et les directions de polarisation mesurées pour différents déports de la source. Les lenteurs apparentes verticales sont définies à partir des temps de trajets verticaux entre au moins deux récepteurs ancrés dans le puits. Les directions de polarisation sont repérées par l'angle Y fait avec la direction verticale. Nous nous sommes intéressé à la propagation des ondes P et SV dans les milieux TI. Quatre constantes élastiques sont nécessaires pour décrire la propagation des ces ondes. Les expressions de la lenteur et de l'angle de polarisation sont donc fonction de quatre constantes élastiques et de l'angle d'incidence O. Pour des milieux anisotropes, cet angle n'est pas directement mesurable à partir de données de puits. On définit alors deux paramètres qui simplifient les expressions de la vitesse de phase et qui permettent d'écrire une relation du type (O = f(Y). À partir de cette relation, on obtient une expression exacte de la lenteur apparente verticale en fonction de l'angle de polarisation. Cette expression est utilisée pour inverser, par une méthode d'optimisation, les paramètres d'anisotropie à partir des données de puits. On détermine, par une étude de sensibilité, dans quelle gamme d'incidence les paramètres seront le plus précisément estimés par cette méthode. On montre de plus comment une erreur sur les données (due aux incertitudes de mesure) se répercute sur les valeurs estimées des paramètres. La méthode d'inversion est testée sur des données synthétiques et sur deux jeux de données réelles. Le premier est un jeu de données enregistré sur le site expérimental de la Colorado School of Mines (White et al., 1983). Le second est un Walkaway enregistré dans le bassin de Paris. Enfin, on définit un modèle permettant de prendre en compte dans le problème inverse, en plus de la lenteur et de la polarisation, la pression mesurée dans le puits. Ce modèle est testé sur des données synthétiques. On montre que la précision sur l'estimation des paramètres est améliorée d'un facteur 5 à 10.

For polluters, America in 1970 was still something of a Wild West. A number of federal, state, and municipal laws aimed at improving air quality were already on the books, but few were enforced, and pollution from the nation’s ever-growing stock of motor vehicles, power plants, and factories remained uncontrolled in much of the country. A passage from the Ralph Nader Study Group’s Vanishing Air, published in May 1970, vividly illustrates the extent to which dirty air was a fact of life for city dwellers of the period: . . . The New Yorker almost always senses a slight discomfort in breathing, especially in midtown; he knows that his cleaning bills are higher than they would be in the country; he periodically runs his handkerchief across his face and notes the fine black soot that has fallen on him; and he often feels the air pressing against him with almost as much weight as the bodies in the crowds he weaves through daily. . . . New York’s problems with air quality were hardly unique. In an October 1969 letter to the Senate Subcommittee on Air and Water Pollution, a resident of St. Louis expressed similar sentiments about the sheer pervasiveness of pollution in her community: . . . What really made me take the time to write this letter was the realization that I had begun to take the haze and various odors for granted. Close the doors and windows and they’ll be less noticeable[. I]t is very disturbing to think I’ve become used to the burning-rubber smell in the evening and the slightly sour smell in the morning. What does air smell like? . . . And air pollution’s costs went far beyond sour smells and dirty handkerchiefs, as a series of deadly “inversions” both here and abroad had made dramatically clear beginning in the late 1940s. Typically, the air at higher altitudes is cooler than that below. This is because the surface of the earth absorbs sunlight and radiates heat, warming the air closest to the ground. That warm surface air then cools as it rises higher into the atmosphere.

Abstract It is now apparent that welds in many of the creep strength enhanced ferritic (CSEF) steel grades are susceptible to Type IV creep damage. Furthermore, due to the complex nature of incubation and growth of localized creep damage in such alloys, state-of-the-practice non-invasive techniques such as hardness, replication and strain measurement alone are insufficient for reliable assessment. Consequently, there is concern in the industry regarding the integrity of existing and proposed installations that utilize CSEF steels such as ASME Grade 91 and Grade 92. To address this concern, in addition to pressing demands for increased efficiency and from environmental regulation, extensive research is underway on various fronts including fracture assessment, online health monitoring and life extension technologies. These rely heavily on the effectiveness of non-destructive testing (NDT) techniques. Therefore, volumetric non-invasive techniques that enable detection and characterization of damage are sought to facilitate effective assessment of welded components operating at high temperature and pressure. Several NDT methods were reviewed in order to understand the current state-of-the-art in terms of their sensitivity to early stage Type IV damage and their readiness for field implementation. Most of the advanced methods proposed for assessment of creep damage are based on the inversion of certain parameters to correlate to the extent of damage. This limits their selectivity, ability to characterize and determine the severity of localized damage. Using recent developments in electronics and signal processing instrumentation, ultrasonic testing was identified as having the potential to be developed as a reliable approach for detection of Type IV creep damage at an early stage. This paper presents the outcome of an industry-focused research effort with the goal of developing and validating an ultrasonic technique for reliable detection of Type IV creep damage at an early stage. In this framework, supported by the Core Research Programme at TWI, an ultrasonic technique was developed and tested on a number of creep-exposed specimens. Ultrasonic data was processed and correlated with controlled metallographic investigations to determine the detection, positioning and characterization performance of Type IV creep damage within the heat affected zone of welds.