Auswahl der wissenschaftlichen Literatur zum Thema „Multiphase flow“

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203977, “Coupling a Geomechanical Reservoir and Fracturing Simulator With a Wellbore Model for Horizontal Injection Wells,” by Shuang Zheng, SPE, and Mukul Sharma, SPE, The University of Texas at Austin. The paper has not been peer reviewed. Reservoir cooling during waterflooding or waste-water injection can alter the reservoir stress field significantly by thermoporoelastic effects. Colloidal particles in the injected water decrease the matrix permeability and build up the injection pressure. Fractures may initiate and propagate from injectors. These fractures are of great concern for environmental reasons and are a strong influence on reservoir sweep and oil recovery. The complete paper introduces methods to fully couple reservoir simulation with wellbore flow models in fractured injection wells. Introduction In this study, a fully integrated 3D geomechanical thermal reservoir simulator is presented. This simulator is fully coupled with a wellbore model and allows fracture propagation. The model accounts for multiphase flow, solid mechanics, thermal stresses, filtration, and fracture growth in coupled reservoir- fracture-wellbore domains and can be used for simulations in both conventional and unconventional reservoirs. The simulator allows study of induced fracture propagation in cased- and openhole injectors while fully accounting for thermoporoelastic and particle-filtration effects. It also allows study of hydraulic fracture propagation in unconventional reservoirs considering the complex wellbore dynamics. The complete paper provides a practical simulation tool to maximize well injectivity while minimizing environmental risks, and to analyze and optimize the completion design in unconventional reservoirs.

Статья посвящена моделированию течения запыленной среды, которое вызвано внутренним электрическим зарядом дисперсной компоненты. В данной работе рассматривается влияние физической плотности материала дисперсных частиц на интенсивность генерируемого в запыленной среде возмущения давления. Применяемая для моделирования процесса математическая модель учитывает скоростную и тепловую неравновесность потока двухфазной среды. Для каждой из компонент смеси решалась полная гидродинамическая система уравнений движения сплошной среды, включавшая в себя уравнения непрерывности, уравнения сохранения пространственных составляющих импульса и уравнения сохранения энергии. Система уравнений динамики многофазной среды решалась с помощью явного конечно-разностного метода второго порядка точности. В результате численного моделирования было выявлено, что увеличение физической плотности материала электрически заряженных частиц приводит к увеличению интенсивности генерируемого акустического возмущения. The article is devoted to modeling the flow of a dusty medium caused by the internal electric charge of a dispersed component. In this paper, we consider the effect of the true density of the dispersed particles material on the intensity of pressure perturbation generated in a dusty medium. The mathematical model used to simulate the process takes into account the velocity and thermal nonequilibrium of the flow of a two-phase medium. For each of the mixture components, we solved a complete hydrodynamic system of continuous medium motion equations that included continuity equations, conservation equations for momentum spatial components, and energy conservation equations. The system of equations of the multiphase medium dynamics was solved using the explicit finite-difference method of the second order of accuracy. As a result of the numerical simulation, it was found that an increase in the true density of the material of electrically charged particles leads to an increase in the intensity of the generated acoustic disturbance.

This PhD thesis focuses on numerical and analytical methods for simulating the dynamics of volcanic ash plumes. The study starts from the fundamental balance laws for a multiphase gas– particle mixture, reviewing the existing models and developing a new set of Partial Differential Equations (PDEs), well suited for modeling multiphase dispersed turbulence. In particular, a new model generalizing the equilibrium–Eulerian model to two-way coupled compressible flows is developed. The PDEs associated to the four-way Eulerian-Eulerian model is studied, investigating the existence of weak solutions fulfilling the energy inequalities of the PDEs. In particular, the convergence of sequences of smooth solutions to such a set of weak solutions is showed. Having explored the well-posedness of multiphase systems, the three-dimensional compressible equilibrium–Eulerian model is discretized and numerically solved by using the OpenFOAM® numerical infrastructure. The new solver is called ASHEE, and it is verified and validated against a number of well understood benchmarks and experiments. It demonstrates to be capable to capture the key phenomena involved in the dynamics of volcanic ash plumes. Those are: turbulence, mixing, heat transfer, compressibility, preferential concentration of particles, plume entrainment. The numerical solver is tested by taking advantage of the newest High Performance Computing infrastructure currently available. Thus, ASHEE is used to simulate two volcanic plumes in realistic volcanological conditions. The influence of model configuration on the numerical solution is analyzed. In particular, a parametric analysis is performed, based on: 1) the kinematic decoupling model; 2) the subgrid scale model for turbulence; 3) the discretization resolution. In a one-dimensional and steady-state approximation, the multiphase flow model is used to derive a model for volcanic plumes in a calm, stratified atmosphere. The corresponding Ordinary Differential Equations (ODEs) are written in a compact, dimensionless formulation. The six non-dimensional parameters characterizing a multiphase plume are then written. The ODEs is studied both numerically and analytically. Different regimes are analyzed, extracting the first integral of motion and asymptotic solutions. An asymptotic analytical solution approximating the model in the general regime is derived and compared with numerical results. Such a solution is coupled with an electromagnetic model providing the infrared intensity emitted by a volcanic ash plume. Key vent parameters are then retrieved by means of inversion techniques applied to infrared images measured during a real volcanic eruption.

L'activité humaine a un impact significatif sur la vadose, une zone située au-dessus des nappes phréatiques, qui n'est que partiellement saturée en eau. La vadose peut être polluée par les activités agricoles ou industrielles, ce qui constitue une menace pour les ressources en eau. De plus, la saturation varie considérablement, notamment en raison des sécheresses plus fréquentes dues au changement climatique. Prévoir le transport de contaminants en milieux insaturées est donc essentiel. Cependant, la compréhension de la dispersion dans les milieux poreux insaturés reste limitée, en raison de l'interaction complexe des flux multiphasiques non miscibles avec le milieu poreux. Les modèles traditionnels tels que le modèle Fickien, décrit par l'équation d'Advection-Diffusion, ne parviennent pas à rendre compte avec précision de la dispersion dans les milieux poreux insaturés. L'objectif est d'aborder la question du transport dans les milieux poreux insaturés en identifiant les propriétés pertinentes à l'échelle du pore pour comprendre la dispersion à plus grande échelle. Il s'agit notamment de déterminer si la dispersion est fickienne ou non-fickienne, ce qui est crucial pour prédire la propagation des polluants. Une double approche est adoptée : des expériences de transport à l'échelle du pore et des simulations de Lattice Boltzmann. La visualisation directe des fluides dans les milieux poreux est un défi. Nous utilisons donc des micromodèles, réseaux poreux transparents interconnectés, pour permettre la visualisation optique à l'échelle du pore. Tout d'abord, un dispositif expérimental micromodèle a été établi et optimisé pour étudier l'écoulement et le transport multiphasiques. Des méthodes d'analyse ont été développées, ainsi que des techniques de caractérisation de la dispersion par l'analyse des moments spatiaux. Une première série d'expériences mène à des résultats préliminaires, l'évolution de la saturation et des distributions de phases avec le nombre capillaire a été caractérisée. Les expériences de transport réalisées pour toute la gamme de saturation montrent que la dispersion augmente à mesure que la saturation diminue. Cependant, l'analyse des faibles saturations s'est avérée difficile en raison de l'augmentation significative de la dispersion et des limites imposées par la taille du micromodèle, empêchant l'étude de la dispersion à long terme. Pour surmonter cette limitation, des simulations Lattice-Boltzmann ont été utilisées pour l'écoulement et le transport, car elles sont flexibles en taille et seulement limitées par le temps de calcul. Toutefois, simuler la distribution de deux phases après un écoulement multiphasique dans un milieu poreux complexe reste un défi. Générer des images à grande échelle de milieux poreux insaturés à partir de données expérimentales s'est donc avéré nécessaire pour observer la dispersion à temps long. Un algorithme de statistique multipoints (MPS) a été utilisé pour générer à la fois des images de milieux poreux non saturés plus larges et un grand ensemble de d'images plus petites pour augmenter la signification statistique de l'étude. Des simulations d'écoulement et de transport ont été réalisées sur l'ensemble des images générées afin d'explorer l'influence de la saturation sur l'écoulement et le transport. Cette étude révèle que la diminution de la saturation augmente de manière significative l'hétérogénéité de l'écoulement, ce qui entraîne une dispersion accrue. Notamment, la nature non fickienne de l'écoulement tend à être plus prononcée à faible saturation. De plus, la transition d'un transport fickien à un transport non fickien dépend du nombre de Peclet. Il existe une compétition entre l'advection et la diffusion dans des conditions saturées, ce qui entraîne un régime Fickien diffusif pour les faibles nombres de Peclet. Cependant, le transport en conditions non saturées est principalement advectif, même à faible nombre de Peclet, et présente donc un comportement non Fickien
Human activity has a significant impact on the vadose zone, an area located below the land surface and above the water tables, only partially saturated with water. The vadose is susceptible to pollution from agricultural or industrial activities, posing a threat to water resources. Plus, saturation levels vary greatly, especially with the increasing frequency of droughts due to climate change. Hence, predicting contaminant transport in unsaturated conditions is crucial. However, the understanding of dispersion in unsaturated porous media remains limited, due to the complex interaction of multiphase non-miscible flows with the porous medium. Traditional models such as the Fickian model, described by the Advection-Diffusion Equation, fail to accurately capture dispersion in unsaturated porous media.The objective is to address the issue of transport in unsaturated porous media by identifying relevant properties at the pore scale to understand dispersion at a larger scale. One of the goals is to determine whether dispersion follows Fickian or non-Fickian behavior, as this understanding is crucial for predicting the spreading of pollutant in the vadose zone.To investigate transport in unsaturated porous media, a dual approach is being employed: pore scale transport experiments and Lattice Boltzmann simulations. Direct visualization of fluid structure in natural porous media is challenging. Thus, we use micromodels, transparent interconnected porous networks, to enable optical visualization at the pore scale. First, a micromodel experimental setup was established and optimized to study multiphase flow and transport. Analysis methods were developed, along with techniques for characterizing dispersion through spatial moment analysis.A series of experiments were conducted to obtain initial results on multiphase flow and dispersion. The evolution of saturation and phase distributions with the capillary number was characterized. Transport experiments were performed for the entire range of saturations, showing that dispersion increases as saturation decreases. However, analyzing low saturations was challenging due to the significant increase in dispersion and limitations imposed by the micromodel size, preventing the study of long-term dispersion.To overcome this limitation, Lattice Boltzmann simulations were used for flow and transport, as there is no size limitation except for computational time. However, simulating the distribution of two phases after a multiphase flow in a complex porous medium remains challenging. Generating large-scale images of unsaturated porous media based on experimental data was then crucial for observing late-time dispersion. Machine learning techniques, specifically the Multiple Point Statistic algorithm, were employed to generate images of wider unsaturated porous media and a large dataset of smaller images to increase the statistical significance of the study.Flow and transport simulations were conducted using the generated image dataset to explore the influence of saturation on flow and transport. This involved examining flow properties under saturated and unsaturated conditions. The nature of transport, specifically whether it exhibited Fickian or non-Fickian behavior was investigated. Furthermore, the effect of the Peclet number (a measure of the balance between advection and diffusion) on dispersion for different saturation levels was analyzed.This study revealed that decreasing saturation significantly increases flow heterogeneity, leading to increased dispersion. Notably, the non-Fickian nature of flow tends to be more pronounced with low saturations. Plus, the transition from Fickian to non-Fickian depends on the Peclet number. There is a competition between advection and diffusion in saturated conditions, resulting in a diffusive Fickian regime for low Peclet numbers. However, transport in unsaturated conditions is mainly advective, even at low Peclet, and thus displays a non-Fickian behavior