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Multiscale Analytical Solutions and Homogenization of n-Dimensional Generalized Elliptic EquationsSviercoski, Rosangela January 2005 (has links)
In this dissertation, we present multiscale analytical solutions, in the weak sense, to the generalized Laplace's equation in Ω ⊂ Rⁿ, subject to periodic and nonperiodic boundary conditions. They are called multiscale solutions since they depend on a coefficient which takes a wide possible range of scales. We define forms of nonseparable coefficient functions in Lᵖ(Ω) such that the solutions are valid for the periodic and nonperiodic cases. In the periodic case, one such solution corresponds to the auxiliary cell problem in homogenization theory. Based on the proposed analytical solution, we were able to write explicitly the analytical form for the upscaled equation with an effective coefficient, for linear and nonlinear cases including the one with body forces. This was done by performing the two-scale asymptotic expansion for linear and nonlinear equations in divergence form with periodic coefficient. We proved that the proposed homogenized coefficient satisfies the Voigt-Reiss inequality. By performing numerical experiments and error analyses, we were able to compare the heterogeneous equation and its homogenized approximation in order to define criteria in terms of allowable heterogeneity in the domain to obtain a good approximation. The results presented, in this dissertation, have laid mathematical groundwork to better understand and apply multiscale processes under a deterministic point of view.
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Integrated adaptive numerical methods for transient two-phase flow in heterogeneous porous mediaChueh, Chih-Che 26 January 2011 (has links)
Transient multi-phase flow problems in porous media are ubiquitous in engineering and environmental systems and processes; examples include heat exchangers, reservoir simulation, environmental remediation, magma flow in the earth crust and water management in porous electrodes of PEM fuel cells. This thesis focuses on the development of accurate and computationally efficient numerical models to simulate such flows. The research challenges addressed in this work fall in two areas. For a numerical standpoint, conventional numerical methods including Newton-Raphson linearization and a simple upwind scheme do not always provide the required computational efficiency or sufficiently accurate resolution of the flow field. From a modelling perspective, closure schemes required in volume-averaged formulations, such as the generalized Leverett J function for capillary pressure, are specific to certain media (e.g. lithologic media) and are not valid for fibrous porous media, which are of central interest in fuel cells.
This thesis presents a set of algorithms that are integrated efficiently to achieve computations that are more than two orders of magnitude faster compared to traditional techniques. The method uses an adaptive operator splitting method based on an a posteriori criterion to separate the flow from the transport equations which eliminates unnecessary and costly solution of the implicit pressure-velocity term at every time step; adaptive meshing to reduce the size of the discretized problem; efficient block preconditioned solver techniques for fast solution of the discrete equations; and a recently developed artificial diffusion strategy to stabilize the numerical solution of the transport equation. The significant improvements in accuracy and efficiency of the approach is demosntrated using numerical experiments in 2D and 3D. The method is also extended to advection-dominated problems to specifically investigate two-phase flow in heterogeneous porous media involving capillary transport. Both hydrophilic and hydrophobic media are considered, and insights relevant to fuel cell electrodes are discussed.
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[en] MODELLING OF FLOW IN POROUS MEDIA / [pt] MODELAGEM PARA ESCOAMENTOS EM MEIOS POROSOSROGERIO MARTINS SALDANHA DA GAMA 04 April 2018 (has links)
[pt] O presente trabalho tem como objetivo a modelagem de escoamentos através de meios porosos, sob o ponto de vista da Teoria Contínua de misturas. O fluido e o sólido, que compõe o meio poroso, são tratados como constituintes contínuos de uma mistura binária, onde não ocorrem reações químicas. Em todas as situações aqui tratadas o fluido é suposto Newtoniano e incompressível, enquanto o meio poroso é rígido, homogêneo e isotrópico. O trabalho pode ser dividido em duas partes principais. Na primeira são modelados escoamentos através de regiões contendo meios porosos saturados e regiões onde só existe o fluido. São discutidas condições de compatibilidade sobre as interfaces, que separam as regiões, e é estabelecido um modelo para escoamentos, nos quais não exista fluxo de massa através das interfaces. A segunda parte trata de escoamentos em meios porosos insaturados, onde é preciso se considerar o efeito de forças capilares. Nesta parte é estabelecido um modelo e são simuladas situações unidimensionais. São estudados vários casos entre eles o enchimento de uma placa porosa, com e sem efeitos de atrito e de forças gravitacionais. A obtenção de resultados, nestes casos, exige a solução numérica de um sistema hiperbólico não-linear de equações diferenciais. / [en] This work aims to a modelling of flow through a porous media based upon the Continuum Theory of Mixtures. The fluid and the solid, which composes the porous media, are assumed as continuous constituent of a binary mixture where chemical reactions do not occur. In all situations here considered, the fluid is assuned Newtonian and incompressíble, while the porous media is rigid, homogeneus and isotropic. This work can be divided in two main parts. In the first one, flows are modelled through regions containing saturated porous media and regions where there is nothing but the fluid. Conditions of compatibility in the interfaces that divide the regions are discussed and a flow modelling is stablished where there are no crosaflow through the interfaces. The second part is concerned with flows in unsaturated porous media, where the effect of capillery pressure is considered. In this Part a model is stablished and unidimensíonal situations are simulated. Several cases are studied and the filling-up of a porous plate is among them,
with and without frictíon effect and gravitational forces. The
obtainment of results, in such cases, requires the numeric
solution of a non-linear hyperbolíc system of differential
equations.
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Monitoring sub-surface storage of carbon dioxideCowton, Laurence Robert January 2017 (has links)
Since 1996, super-critical CO$_2$ has been injected at a rate of $\sim$0.85~Mt~yr$^{-1}$ into a pristine, saline aquifer at the Sleipner carbon capture and storage project. A suite of time-lapse, three-dimensional seismic reflection surveys have been acquired over the injection site. This suite includes a pre-injection survey acquired in 1994 and seven post-injection surveys acquired between 1999 and 2010. Nine consistently bright reflections within the reservoir, mapped on all post-injection surveys, are interpreted to be thin layers of CO$_2$ trapped beneath mudstone horizons. The areal extents of these CO$_2$ layers are observed to either increase or remain constant with time. However, volume flux of CO$_2$ into these layers has proven difficult to measure accurately. In addition, the complex planform of the shallowest layer, Layer 9, has proven challenging to explain using reservoir simulations. In this dissertation, the spatial distribution of CO$_2$ in Layer~9 is measured in three dimensions using a combination of seismic reflection amplitudes and changes in two-way travel time between time-lapse seismic reflection surveys. The CO$_2$ volume in this layer is shown to be growing at an increasing rate through time. To investigate CO$_2$ flow within Layer~9, a numerical gravity current model that accounts for topographic gradients is developed. This vertically-integrated model is computationally efficient, allowing it to be inverted to find reservoir properties that minimise differences between measured and modelled CO$_2$ distributions. The best-fitting reservoir permeability agrees with measured values from nearby wells. Rapid northward migration of CO$_2$ in Layer~9 is explained by a high permeability channel, inferred from spectral decomposition of the seismic reflection surveys. This numerical model is found to be capable of forecasting CO$_2$ flow by comparing models calibrated on early seismic reflection surveys to observed CO$_2$ distributions from later surveys. Numerical and analytical models are then used to assess the effect of the proximity of an impermeable base on the flow of a buoyant fluid, motivated by the variable thickness of the uppermost reservoir. Spatial gradients in the confinement of the reservoir are found to direct the flow of CO$_2$ when the current is of comparable thickness to the reservoir. Finally, CO$_2$ volume in the second shallowest layer, Layer~8, is measured using structural analysis and numerical modelling. CO$_2$ in Layer~8 is estimated to have reached the spill point of its structural trap by 2010. CO$_2$ flux into the upper two layers is now $\sim$40\% of total CO$_2$ flux injected at the base of the reservoir, and is increasing with time. This estimate is supported by observations of decreasing areal growth rate of the lower layers. The uppermost layers are therefore expected to contribute significantly to the total reservoir storage capacity in the future. CO$_2$ flow within Layer~9 beyond 2010 is forecast to be predominantly directed towards a topographic dome located $\sim$3~km north of the injection point. This dissertation shows that advances in determining the spatial distribution and flow of CO$_2$ in the sub-surface can be made by a combination of careful seismic interpretation and numerical flow modelling.
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Verification of a Three-Dimensional Resin Film Infusion Proecss Simulation ModelCaba, Aaron C. Jr. 05 March 1998 (has links)
This investigation completed the verification of a three-dimensional resin transfer molding/resin film infusion (RTM/RFI) process simulation model. The model incorporates resin flow through an anisotropic carbon fiber preform, cure kinetics of the resin, and heat transfer within the preform/tool assembly. The computer model can predict the flow front location, resin pressure distribution, and thermal profiles in the modeled part.
The formulation for the flow model is given using the finite element/control volume (FE/CV) technique based on Darcy's Law of creeping flow through a porous media. The FE/CV technique is a numerically efficient method for finding the flow front location and the fluid pressure. The heat transfer model is based on the three-dimensional, transient heat conduction equation, including heat generation. Boundary conditions include specified temperature and convection. The code was designed with a modular approach so the flow and/or the thermal module may be turned on or off as desired. Both models are solved sequentially in a quasi-steady state fashion.
A mesh refinement study was completed on a one-element thick model to determine the recommended size of elements that would result in a converged model for a typical RFI analysis. Guidelines are established for checking the convergence of a model, and the recommended element sizes are listed.
Several experiments were conducted and computer simulations of the experiments were run to verify the simulation model. Isothermal, non-reacting flow in a T-stiffened section was simulated to verify the flow module. Predicted infiltration times were within 12-20 percent of measured times. The predicted pressures were approximately 50 percent of the measured pressures. A study was performed to attempt to explain the difference in pressures.
Non-isothermal experiments with a reactive resin were modeled to verify the thermal module and the resin model. Two panels were manufactured using the RFI process. One was a stepped panel and the other was a panel with two `T' stiffeners. The difference between the predicted infiltration times and the experimental times was 4 to 23 percent. / Master of Science
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[pt] MECANISMOS QUE GOVERNAM A EFETIVIDADE DE AGENTES OBTURANTES NO CONTROLE DA INVASÃO DE FLUIDOS DE PERFURAÇÃO NA ROCHA RESERVATÓRIO DE PETRÓLEO / [en] THE DRIVING MECHANISMS FOR BRIDGING AGENTS EFFECTIVENESS ON DRILLING FLUIDS INVASION CONTROL INTO OIL RESERVOIR ROCKSALEX TADEU ALMEIDA WALDMANN 06 January 2006 (has links)
[pt] Este estudo procurou observar e quantificar os parâmetros
operacionais que
governam as propriedades permoporosas da torta de
filtração, formada após o
escoamento de uma solução de glicerina com uma determinada
concentração de
sólidos. A formação de um reboco externo de baixa
permeabilidade é um dos
fatores mais importantes para minimizar da invasão do
filtrado de fluido na rocha
reservatório. A contaminação do reservatório pelo filtrado
do fluido pode trazer
vários problemas operacionais, que serão discutidos nesta
dissertação. A eficiência
do sistema de fluidos em minimizar a invasão é normalmente
avaliada através de
ensaios padrão de filtração estática. Neste trabalho dois
objetivos centrais são
definidos: Identificar os parâmetros operacionais que
governam as propriedades
permoporosas do reboco externo através de ensaios de
filtração estática e
disponibilizar uma metodologia para a avaliação da invasão
do filtrado do fluido de
perfuração na geometria poço-reservatório (escoamento
radial), a partir de ensaios
de laboratório de filtração estática (escoamento linear).
Os resultados indicam que
a solução da lei Darcy para o problema de filtração com
formação de torta
incompressível mostrou - se adequada para grande maioria
dos ensaios
experimentais com solução de glicerina contendo agentes
obturantes. O mesmo
não se verificou para ensaios com solução de goma xantana
como meio contínuo.
Os resultados experimentais obtidos mostraram também que,
para uma mesma
solução de glicerina contendo agente obturante, os valores
de permeabilidade da
torta de filtração obtidos na geometria linear e na
geometria radial são
semelhantes. Desta forma, pode - se validar a metodologia
de previsão do grau da
invasão de fluidos de perfuração na rocha reservatório
(configuração radial) a partir
de ensaios convencionais de laboratório (configuração
linear). / [en] This work deals with the understanding of the major
operational parameters
governing filter cake building drilling fluids invasion
through reservoir rocks. The
ability of the fluid system to prevent invasion is
normally evaluated by standardized
static filtration experiments. In these tests, the fluid
is pressurized through a filter
paper or into a consolidated inert porous medium. The
volume which crosses the
porous core is monitored along the time. Darcy flow
modeling of non-compressible
cakes proved to reproduce adequately the filtration of a
Newtonian fluid +
particulate system through ceramic and sinterized steel
disks. Pressure differential,
particle size and shape proved to be relevant parameters
affecting filter cake
permeability and porosity. The present study proposes,
through the coupling of a
linear filtration formulation (lab configuration) and a
radial single phase formulation
(wellbore vicinity), to predict fluid invasion depth of
fluid filtrate in the reservoir rock.
Modeling is validated with linear and radial lab tests.
The proposed methodology is
a requirement for optimum drilling fluid design to be used
in the drilling of reservoir
sections in both exploratory and development wells.
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[en] FLOW OF OIL-IN-WATER EMULSIONS THROUGH CONSTRICTED CAPILLARIES / [pt] ESCOAMENTO DE EMULSÕES ÓLEO- ÁGUA ATRAVÉS DE CAPILARES COM GARGANTASYGIFREDO COBOS URDANETA 14 February 2008 (has links)
[pt] O escoamento de emulsões é encontrado em diversos
processos de recuperação e produção de petróleo. O
escoamento de emulsões em meios porosos
depende de diversos parâmetros como a relação do tamanho
das gotas
ao tamanho dos poros, a razão de viscosidades, a vazão
volumétrica e o
efeito destes parâmetros ainda não é bem compreendido.
Uma
análise detalhada
na escala microscópica dos fenômenos envolvidos se faz
essencial
para a melhora do entendimento completo do escoamento de
emulsões em
um reservatório. Isto permitiria o desenvolvimento de
melhores modelos de
simulação para o escoamento multifísico em meios porosos.
Neste trabalho,
o escoamento de emulsões óleo-água através de um capilar
com garganta foi
estudado através de experimentos e teoria. A análise
experimental consistiu
da visualização sob um microscópio do escoamento e da
medição da queda
de pressão em função da vazão para diferentes emulsões. A
análise teórica
englobou o estudo do escoamento em regime permanente de
uma gota de
óleo imersa em água através de um capilar e o estudo do
escoamento transiente
da mesma gota através de um capilar com uma garganta. Os
resultados
mostram que os modelos de escoamento de emulsões em meios
porosos não
devem ser baseados em propriedades macroscópicas da
emulsão quando o
tamanho das gotas da fase dispersa for da mesma ordem de
grandeza do
tamanho dos poros. Neste caso, a queda de pressão é
função
da tensão interfacial,
a razão de viscosidades, a vazão e a razão entre o
tamanho
das gotas
e o diâmetro do poro. Os resultados apresentados neste
trabalho podem ser
usados no projeto de emulsões apropriadas para controle
de
mobilidade em
operações de recuperação avançada através de injeção de
emulsões. / [en] Flow of emulsions is found in many petroleum recovery and
production processes
and it is often referred to in the context of tertiary oil
recovery. The
characteristics of emulsion flow in porous media depend on
several parameters
such as medium drop size to pore size ratio, viscosity
ratio, flow rate
and the effect of these parameters is far from being
entirely understood. A
detailed analysis at a microscopic scale of the flow is
essential to improve
the understanding of flow of an emulsion in a reservoir.
This would lead
to the development of better simulation models, henceforth
increasing the
predictability capability of reservoir simulators for
enhanced oil recovery
applications. In this work, flow of oil-water emulsions
through constricted
capillaries, used as model for the geometry inside a
porous media, is studied
experimentally and theoretically. The experimental
approach consisted
of measuring pressure drop response as a function of flow
rate for different
emulsions and visualizing the flow under an optical
microscope to understand
the phenomena involved. The theoretical approach is
divided in two
parts. First, the immiscible steady flow of a infinite
single drop suspended in
an less viscous fluid through a capillary was analyzed by
solving the Navier-
Stokes equations with the appropriate boundary conditions
for free-surface
flow. The second part of the theoretical analysis
consisted of solving the
transient flow of a drop suspended in a less viscous fluid
through a capillary
with a constriction. It is shown the effect of capillary
number and viscosity
ratio over the main responses of the flow. The results
show that models
of emulsion flow in a porous media cannot be based on the
macroscopic
properties of the emulsion when the drop diameter is of
the same order
of magnitude as the pore throat diameter. In this case
flow rate-pressure
drop is a strong function of the interfacial tension,
viscosity ratio, flow rate
and drop to pore size ratio. The results can be used to
design appropriate
emulsions to control the water mobility during EOR
operations by emulsion
injection.
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Métodos de elementos finitos híbridos aplicados a escoamentos miscíveis em meios porosos heterogêneos / Hybrid-mixed finite element method for miscible displacements in heterogeneous porous mediaRODRIGUEZ NUNEZ, Yoisell 04 September 2014 (has links)
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Previous issue date: 2014-09-04 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes) / Fundação de Apoio ao Desenvolvimento da Computação Científica (FACC) / The numerical simulation of incompressible miscible displacements in porous media has obtained significant progress in the last decades being an useful tool in several areas of interest. In particular, in the oil industry the use of numerical simulation allows to obtain qualitative and quantitative data that may provide a better understanding of the physical and chemical processes that occur, for example, in petroleum reservoirs.
The system of partial differential equations governing miscible displacement consists of an elliptic subsystem stemming from conservation of mass, Darcy’s law and a transport equation expressing the conservation of the injected fluid (concentration). Although the concentration is the variable of greatest interest, the calculation of the velocity field requires special attention since it is responsible for transporting the mixture and, therefore, its production. Besides, it has a strong influence on the stability and accuracy of the transport equation when we are dealing with adverse mobility ratios, that is, the solvent is less viscous than the resident oil. These facts motivate us to seek for an efficient and accurate numerical method for the calculation of the velocity field (Darcy’s system) in order to reduce inaccuracies in calculating the concentration.
In this thesis we propose a Stabilized Dual Hybrid Mixed (SDHM) method to approximate the Darcy subsystem. It is shown that this methodology is stable with usual finite element approximations, such as Lagrangian polynomial approximations, where all variables can be interpolated by equal-order functions. Furthermore, the SDHM method is conservative with appropriate parameters choices, and more accurate and robust when compared to the Galerkin method and postprocessing techniques.
In order to verify the efficiency of the SDHM method, computer simulations are presented for the recovery processes of reservoirs for patterns flow problems in homogeneous and heterogeneous porous media, such as tracer injection and continuous injection. The SDHM method is employed together with a combination of the SUPG method in the spatial discretization, and an implicit finite difference scheme in the time for the concentration approximation of the transport equation.
To verify the proposed methodology a semi-analytical approach is also employed which combines the SDHM approximation for velocity field with the concentration calculated analytically by the streamline method. The results obtained with the proposed formulation showed to be efficient, accurate and free of spurious oscillations even for highly heterogeneous scenarios, where we consider random permeability and adverse mobility ratios. / A simulação numérica de deslocamentos miscíveis incompressíveis em meios porosos obteve avanços significativos nas últimas décadas, sendo uma ferramenta útil em várias áreas de interesse. Em particular, na indústria do petróleo, a utilização de simulação numérica permite obter dados qualitativos e quantitativos que podem proporcionar uma melhor compreensão dos processos físicos e químicos que ocorrem, por exemplo, em reservatórios de petróleo.
O sistema de equações diferenciais parciais que regem o deslocamento miscível consiste em um subsistema elíptico, decorrente de conservação de massa, a lei Darcy, e uma equação de transporte, que expressa a conservação do fluido injetado(concentração). Embora a concentração é a variável de maior interesse, o cálculo do campo de velocidade requer uma atenção especial, uma vez que é responsável pelo transporte da mistura e, por conseguinte, a produção da mesma. Além disso,o campo de velocidades tem uma forte influência sobre a estabilidade e a precisão da equação de transporte quando estamos lidando com razões de mobilidade adversas.
Esses fatos nos motivam a procurar um método numérico eficiente e preciso para o cálculo do campo de velocidade (subsistema de Darcy), a fim de reduzir as viii imprecisões no cálculo da concentração.
Nesta tese propomos um método Misto Híbrido Dual Estabilizado (MHDE) para aproximar o subsistema de Darcy. Mostra-se que essa metodologia é estável com aproximações de elementos finitos usuais, tais como aproximações polinomiais de Lagrange, onde todas as variáveis podem ser interpoladas por funções de igual ordem. Além disso, o método MHDE é conservativo, para escolhas adequadas dos parâmetros de estabilização, e mais preciso e robusto em comparação ao método de Galerkin e técnicas de pós-processamento.
Com o intuito de verificar a eficiência do método MHDE, são apresentadas simulações computacionais para os processos de recuperação de reservatórios, para problemas padrões de escoamentos em meios porosos homogêneos e heterogêneos, tais como: injeção de traçadores e injeção continua. É empregado o método MHDE juntamente com uma combinação do método SUPG, na discretização espacial, e um esquema implícito de diferenças finitas no tempo, para a aproximação da concentração da equação de transporte. Outra abordagem, denominada semianalítica,utilizada na validação da metodologia proposta, consiste na combinação do campo de velocidades obtidos pelo método MHDE com a concentração calculada analiticamente pelo método das linhas de fluxo. Os resultados obtidos com a formulação proposta mostram-se eficientes, acurados e livres de oscilações espúrias até para os cenários altamente heterogêneos, onde consideramos permeabilidades aleatórias e razões de mobilidades adversas.
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O Problema de Riemann para um escoamento bifásico em meios porosos com histerese nas duas fases. / The Riemann Problem for a two-phase flow in porous media with hysteresis in the two phases.ARAÚJO, Juliana Aragão de. 05 July 2018 (has links)
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Previous issue date: 2005-05 / Neste trabalho é apresentada a solução do problema de Riemann associado a um
sistema de leis de conservação. Este sistema é proveniente de um escoamento bifásico
unidimensional em meios porosos e considera os efeitos de histerese nas curvas de
permeabilidade das fases. A principal contribuição deste trabalho é que a solução do
problema de Riemann é obtida para um modelo que leva em conta a histerese nas duas
fases e que considera as curvas de embebição e de drenagem distintas sempre que haja
uma reversão de regime de drenagem para embebição e vice-versa. Os resultados obtidos aqui ampliam aqueles obtidos para um modelo mais simplificado em que a histerese era considerada apenas numa das fases e as curvas de permeabilidade eram tomadas coincidentes após urna segunda reversão. Uma vez obtida a solução do problema de Riemann, base para a construção de simuladores numéricos de alta precisão, é feita uma comparação entre esta solução e aquela obtida anteriormente, para os mesmo dados iniciais, mostrando que não só as velocidades de ondas podem ser distintas, mas também as próprias sequências de ondas que formam tais soluções. / In this work we prasent the Riemann solution for a system of conservation laws
associatcd to an unidimensional two-ph&sc fiow in a porous media taking into account
the hysteresis effects on the permeability curves. Our main contribution in this work
is that the solution of the Riemann problem is obtained for a model that takes into account
the hysteresis in both wetting and non-wetting phases and considers the scanning
curves of embebition and drainagc distincts whenever there is a reversion of regime.
The results obtained here improve those obtained for a simplified model where hysteresis
is considered only on the non-wetting phase and the scanning curves coincide aftcr
a second reversion of regime. Once obtained the solution of the Riemann problem,
which is basic for the construction of high aceurate numeric simulators, we compare
this solution and that one already obtained, for the same initial data. showing that
not only the speeds of waves can be distinct, but also the sequences of waves in such
Solutions.
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Imbibition forcée en milieu poreux / Forced Imbibition Through Porous MediaOdier, Céleste 19 October 2017 (has links)
La compréhension des écoulements biphasiques dans des milieux hétérogènes est déterminante pour un certain nombre de processus industriels. Le plus marquant étant la récupération assistée du pétrole piégé dans des roches poreuses,qui est un moteur pour la recherche dans ce domaine depuis plusieurs décennies.Pourtant, si l’imbibition spontanée de liquides dans un milieu poreux est relativement bien comprises, l’imbibition forcée d’un liquide dans un milieu poreux rempli d’un liquide plus visqueux n’a pas encore été décrite quantitativement. En combinant des expériences de microfluidique et d’imagerie confocale, nous avons étudié la morphologie et la dynamique d’imbibition forcée dans des milieux poreux réguliers. Nous avons mis en évidence la présence de quatre régimes d’imbibition,provenant de dynamiques d’invasion différentes à l’échelle du pore et ayant une signature claire sur les observables macroscopiques. L’étude de la dynamique locale associée à la microscopie confocale, qui donne accès à des informations tridimensionnelles,nous a permis de montrer que les transitions entre ces régimes étaient la conséquence de deux transitions de mouillage et d’une instabilité d’interface.De plus, contrairement à la majorité des études menées jusqu’à présent, nous nous sommes intéressés à l’évolution de ces motifs d’imbibition soumis à une injection continue sur des temps longs devant le temps de percolation. Cela a permis de mettre en évidence le vieillissement de ces motifs qui est le résultat d’un mûrissement d’origine capillaire. / Understanding two-phase flow in heterogeneous media is of great importance for a number of industrial processes. One of the most prominent examples is enhanced oil recovery which has driven fundamental and applied research in this fieldfor decades. However our understanding has remained extremely unbalanced. The case of spontaneous imbibition of a fluid in a porous medium is fairly well understood,whereas quantitative descriptions of forced imbibition in the presence of anunfavorable viscosity ratio is still lacking. Combining large-scale observations and confocal imaging of microfluidic experiments, we studied the morphology and dynamicsof forced imbibition in homogeneous porous media. We identify four classesof three-dimensional patterns resulting from different dynamics at the pore-scale, and having a clear signature on the macroscopic observables. By means of confocalmicroscopy allowing us to visualize three dimensional features of the local dynamics,we show that the transitions between the four imbibition scenarios result from two dynamical wetting transitions and one interfacial instability. In addition,unlike previous studies, we investigate the evolution of those patterns undercontinuous injection over long time scales. We evidence their aging according to acapillary-coarsening process.
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