Understanding the physics of water evaporation from saline porous media is important in many processes such as soil salinity, terrestrial ecosystem functioning, vegetation and crop production, biological activities in vadose zone, and CO2 sequestration. Precipitation of salt is one of the possible outcomes of the evaporation process from saline porous media which may either enhance or interrupt the desired process depending on the localization and pattern of the precipitated salt. In the present study X-ray micro tomography was used to study the 3D dynamics and patterns of salt deposition in drying porous media under different boundary conditions and the effects of salt concentration, particle size distribution and shape of grains on the precipitation patterns and dynamics at pore-scale have been investigated. Evaporation process from porous media involves preferential invasion of large pores on the surface while the fine pores remain saturated serving as the evaporation sites to supply the evaporative demand. This results in increasing salt concentration in fine pores during evaporation. Precipitation starts when salt concentration exceeds the solubility limit in the preferential evaporation sites. At the early stages, the precipitation rate increases with time until all evaporation sites at the surface reach the solubility limit and turn into the precipitation sites. This is followed by a constant rate of precipitation proportional to the evaporation rate. We show that the formation of salt crust at the surface does not immediately interrupt the evaporation process due to the porous nature of the precipitated salt investigated using the scanning electron microscopy. Also, our results confirmed the formation of discrete efflorescence at the surface of porous media due to the presence of pores with different sizes. Distribution of these fine pores on the surface directly influences the patterns of salt precipitation and thickness of the salt crust such that in the media with more fine pores, precipitated salt forms a thinner crust as the solute transferred to the surface is distributed among more evaporation sites. In contrast, in the media with fewer evaporation sites at the surface the salt crust will be more discrete but thicker. A simple equation is also proposed to estimate the evolution if the thickness of the salt crust on the surface of porous media. Our results provide new insights regarding the physics of salt precipitation and its complex dynamics in porous media during evaporation.

Des phénomènes de colmatage de la structure granulaire des réservoirs pétroliers sont observés lors de la réinjection d'eau de production dans le réservoir (endommagement hydrique). Le dépôt des particules solides en suspension dans l'eau de production peut engendrer une réduction de la perméabilité du réservoir notamment autour des puits d'injection. Il en résulte une diminution significative de l'injectivité des puits. L'objectif de cette thèse est d'étudier le processus de transport et de dépôt des particules solides dans un réservoir de sable et son influence sur la perméabilité du milieu. Nous étudions également l'influence de certains paramètres tels que : la concentration en particules, le débit d'injection, la taille de particules injectées, la taille des pores du milieu et la rugosité de la surface des grains. La finalité de ce travail est de proposer un modèle prédictif de transport-dépôt-endommagement afin de pouvoir estimer la pérennité du système. Dans ce but, une campagne d'essais expérimentaux est menée sur le processus de transport et de dépôt des particules siliceuses de taille de quelques microns dans une éprouvette de sable dense. Ces essais ont été réalisés sur trois dispositif différents ; deux dispositifs d'injection unidimensionnelle (colonne d'injection et cellule d'injection) et un dispositif d'injection radiale en chambre d'étalonnage en vue de simuler les conditions d'injection en puits. Dans ces essais, les conditions hydrauliques sont contrôlées et la concentration en particules dans la suspension est imposée. Au cours de l'injection, le suivi de l'évolution de la pression interstitielle est réalisé en utilisant des capteurs de pression installés à différents endroits dans le milieu. La concentration des particules dans le fluide sortant est mesurée en utilisant un turbidimètre installé à la sortie du milieu. L'étude expérimentale réalisée sous différentes conditions a permis de mettre en évidence une forte hétérogénéité du dépôt des particules dans le milieu poreux. Cette hétérogénéité se traduit par la formation d'un cake interne et/ou externe au voisinage du point d'injection. L'analyse de ce cake montre un milieu à double porosité avec deux familles de pores correspondant à la porosité interne des agglomérats formés par les particules déposées et la porosité du sable réduite progressivement par le dépôt de ces derniers. Une étude paramétrique a permis de mettre en évidence une distinction entre l'effet des faibles et des fortes concentrations, ainsi que l'importance de l'effet du débit d'injection, de la taille des pores, de la taille des particules de la suspension ainsi que de la rugosité de la surface des grains. Ce travail expérimental s'accompagne d'une modélisation des phénomènes de transport et de dépôt des particules dans un milieu poreux. Dans un premier temps, nous avons utilisé un modèle de convection dans lequel la loi décrivant le dépôt des particules prend en compte la densité des particules déposées ainsi que le relargage des particules. Les paramètres de la loi constitutive de dépôt, ainsi qu'une loi empirique porosité-perméabilité ont été calibrés en simulant les résultats expérimentaux d'essais d'injection en cellule sous différentes conditions. Un nouveau modèle semi analytique basé sur le modèle d'Eylander (1988) a été développé dans lequel nous prenons en compte une distribution spatiale des particules déposées et une double porosité du milieu (cake et milieu granulaire). Cette distribution est inspirée du modèle convection étudié auparavant. La simulation d'essais d'injection en cellule a permis de montrer les capacités du modèle pour la prédiction des variations de la pression en cours de l'essai. Ce modèle permet une prédiction de l'évolution de la perméabilité pendant l'injection de façon plus simple et directement applicable dans l'ingénierie de réservoirs / Hydraulic damage and plugging of the granular structure of oil reservoirs are commonly observed during the re-injection of produced water. These phenomena can lead to a significant decrease of the reservoir permeability around the injectors and affect the injectivity of these wells. The objective of this thesis is to study the transport and deposition process of solid particles in a sand reservoir and its influence on the permeability of the medium. We also study the influence of certain parameters such as particle concentration, injection flow rate, the size of injected particles, the pore size of the medium and the surface roughness of the grains. The aim of this work is to propose a predictive model of transport-deposition-damage in order to estimate the durability of the system. For this purpose, an experimental program was conducted on the transport and deposition process of the siliceous particles of size of a few microns in dense sand specimens. These tests were carried out on three different devices; two one-dimensional injection devices (injection column and injection cell) and a radial injection device in “chambre d'étalonnage” in order to simulate the injection wells conditions. In these tests, the flow conditions are controlled and the concentration of particles in the suspension is imposed. During injection, the monitoring of the evolution of pore pressure is carried out using pressure sensors located in different places in the medium. The particle concentration in the outgoing fluid is measured using a turbidimeter installed at the outlet. The experimental study carried out under different conditions allowed to highlight a highly heterogeneous particle deposition in the porous medium. This heterogeneity results in the formation of an internal and/or external cake in the vicinity of the injection point. The analysis of this cake shows a double porosity medium with two pore families corresponding to the internal porosity of the agglomerates formed by the deposited particles and porosity of the sand gradually reduced by the particles deposition. A parametric study permitted to show a distinction between the effect of low and high particles concentrations, as well as the importance of the effect of injection flow rate, the pore size, the particle size of the suspension and the roughness of the surface of the grains. This experimental work is associated with modelling of transport and deposition of particle in a porous medium. We used first the convection model in which a constitutive law describing the particle deposition takes into account the effects of the deposited particles concentration and the release of particles. The parameters of the particle deposition constitutive law as well as an empirical porosity-permeability law have been calibrated by simulation of the results of injection tests performed in the injection cell under different conditions. A semi-analytical model based on the Eylander (1988) model was developed in which we take into account a spatial distribution of the deposited particles and a double porosity of the medium (cake and granular medium). This distribution is inspired from the results if convection model studied before. The simulation of the results of injection experiments permitted to show the performances of this model for prediction of the pore pressure evolution during the fluid injection. This model allows prediction of the permeability evolution in a simpler and directly applicable manner in the reservoir engineering

Orientadores: Euclides Jose Bonet, Kamal Abdel Radi Ismail / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T01:56:31Z (GMT). No. of bitstreams: 1 PompeoNeto_LuizBenedicto_M.pdf: 311727 bytes, checksum: f5aafe4c0c4ba7418df2f2fc710c02a8 (MD5) Previous issue date: 2004 / Resumo: Neste trabalho foram verificados experimentalmente os efeitos da vibração mecânica na permeabilidade absoluta de meios porosos saturados com água e sob a imposição simultânea de um escoamento uniforme. Após a identificação de uma faixa de excitação em que se excluem efeitos indiretos da vibração, como os decorrentes do aquecimento ultra-sônico do conjunto e da desintegração mecânica da matriz rochosa, foi possível verificar que a vibração a freqüências ultra-sônicas reduz a diferença de pressão ao longo da amostra e reduz a vazão através da amostra. A combinação de magnitude desses dois efeitos pode resultar em aumento da permeabilidade absoluta, sendo que as variações, além da freqüência, ainda dependem da velocidade do escoamento externamente imposto. A análise do problema através da mecânica do contínuo permitiu introduzir a descrição de um modelo físico, baseado no conceito da película viscosa de espessura inversamente proporcional à freqüência. O mecanismo é capaz de explicar o comportamento observado. Os fenômenos mostraram-se decorrência das propriedades elásticas, dadas as propriedades hidrodinâmicas, do sistema composto pela matriz sólida e pelo fluido que preenche o meio poroso saturado e por ele escoa / Abstract: This work verifies experimentally the effects of the mechanical vibration on the absolute permeability of saturated porous media upon which a uniform flow is simultaneously imposed. After finding a driving range within which indirect effects of the vibration are excluded, such as those resulting from ultrasonic heating and mechanical disintegration of the rock matrix, it was possible to verify that vibration at ultrasonic frequencies reduces the pressure drop across the sample and reduces the flow rate through it. The combination of amplitude of both these effects may result the improvement of the absolute permeability. Besides depending on the frequency, such changes depend on the velocity of the externally imposed flow. Analysis of the problem making use of continuum mechanics permitted introducing the description of a physical model, based on the concept of the viscous skin depth inversely proportional to the frequency. The mechanism is capable of explaining the observed behavior. The phenomena turned out to result from the elastic properties ¿ given the hydrodynamic properties ¿ of the system composed by the solid matrix together with the fluid, which fills and flows through the saturated porous medium / Mestrado / Instrumentação e Controle Industrial / Mestre Profissional em Engenharia Mecanica

No description available.

The mathematical model that has been recognized to have the more accurate approximation to the physical laws govern subsurface hydrocarbon flow in reservoirs is the Compositional Model. The features of this model are adequate to describe not only the performance of a multiphase system but also to represent the transport of chemical species in a porous medium. Its importance relies not only on its current relevance to simulate petroleum extraction processes, such as, Primary, Secondary, and Enhanced Oil Recovery Process (EOR) processes but also, in the recent years, carbon dioxide (CO2) sequestration. The purpose of this study is to investigate the subsurface compositional flow under isothermal conditions for several oil well cases. While simultaneously addressing computational implementation finesses to contribute to the efficiency of the algorithm. This study provides the theoretical framework and computational implementation subtleties of an IMplicit Pressure Explicit Composition (IMPEC)-Volume-balance (VB), two-phase, equation-of-state, approach to model isothermal compositional flow based on the finite difference scheme. The developed model neglects capillary effects and diffusion. From the phase equilibrium premise, the model accounts for volumetric performances of the phases, compressibility of the phases, and composition-dependent viscosities. The Equation of State (EoS) employed to approximate the hydrocarbons behaviour is the Peng Robinson Equation of State (PR-EOS). Various numerical examples were simulated. The numerical results captured the complex physics involved, i.e., compositional, gravitational, phase-splitting, viscosity and relative permeability effects. Regarding the numerical scheme, a phase-volumetric-flux estimation eases the calculation of phase velocities by naturally fitting to phase-upstream-upwinding. And contributes to a faster computation and an efficient programming development.

No description available.

abstract: The potential of using bio-geo-chemical processes for applications in geotechnical engineering has been widely explored in order to overcome the limitation of traditional ground improvement techniques. Biomineralization via urea hydrolysis, referred to as Microbial or Enzymatic Induced Carbonate Precipitation (MICP/EICP), has been shown to increase soil strength by stimulating precipitation of calcium carbonate minerals, bonding soil particles and filling the pores. Microbial Induced Desaturation and Precipitation (MIDP) via denitrification has also been studied for its potential to stabilize soils through mineral precipitation, but also through production of biogas, which can mitigate earthquake induced liquefaction by desaturation of the soil. Empirical relationships have been established, which relate the amount of products of these biochemical processes to the engineering properties of treated soils. However, these engineering properties may vary significantly depending on the biomineral and biogas formation mechanism and distribution patterns at pore-scale. This research focused on the pore-scale characterization of biomineral and biogas formations in porous media. The pore-scale characteristics of calcium carbonate precipitation via EICP and biogenic gas formation via MIDP were explored by visual observation in a transparent porous media using a microfluidic chip. For this purpose, an imaging system was designed and image processing algorithms were developed to analyze the experimental images and detect the nucleation and growth of precipitated minerals and formation and migration mechanisms of gas bubbles within the microfluidic chip. Statistical analysis was performed based on the processed images to assess the evolution of biomineral size distribution, the number of precipitated minerals and the porosity reduction in time. The resulting images from the biomineralization study were used in a numerical simulation to investigate the relation between the mineral distribution, porosity-permeability relationships and process efficiency. By comparing biogenic gas production with abiotic gas production experiments, it was found that the gas formation significantly affects the gas distribution and resulting degree of saturation. The experimental results and image analysis provide insight in the kinetics of the precipitation and gas formation processes and their resulting distribution and related engineering properties. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2019

An editorial and a selection of papers presented at the 14th International Bologna Conference Magnetic Resonance in Porous Media (MRPM 14), February 2018, Gainesville, FL, USA

ABSTRACT Modeling Diffusion and Buoyancy-Driven Convection with Application to Geological CO2 Storage Rebecca Allen Geological CO2 storage is an engineering feat that has been undertaken around the world for more than two decades, thus accurate modeling of flow and transport behavior is of practical importance. Diffusive and convective transport are relevant processes for buoyancy-driven convection of CO2 into underlying fluid, a scenario that has received the attention of numerous modeling studies. While most studies focus on Darcy-scale modeling of this scenario, relatively little work exists at the pore-scale. In this work, properties evaluated at the pore-scale are used to investigate the transport behavior modeled at the Darcy-scale. We compute permeability and two different forms of tortuosity, namely hydraulic and diffusive. By generating various pore ge- ometries, we find hydraulic and diffusive tortuosity can be quantitatively different in the same pore geometry by up to a factor of ten. As such, we emphasize that these tortuosities should not be used interchangeably. We find pore geometries that are characterized by anisotropic permeability can also exhibit anisotropic diffusive tortuosity. This finding has important implications for buoyancy-driven convection modeling; when representing the geological formation with an anisotropic permeabil- ity, it is more realistic to also account for an anisotropic diffusivity. By implementing a non-dimensional model that includes both a vertically and horizontally orientated 5 Rayleigh number, we interpret our findings according to the combined effect of the anisotropy from permeability and diffusive tortuosity. In particular, we observe the Rayleigh ratio may either dampen or enhance the diffusing front, and our simulation data is used to express the time of convective onset as a function of the Rayleigh ratio. Also, we implement a lattice Boltzmann model for thermal convective flows, which we treat as an analog for CO2 storage modeling. Our model contains the multiple- relaxation-time scheme and moment-based boundary conditions to avoid the numer- ical slip error that is associated with standard bounce-back. The model’s accuracy and robustness is demonstrated by an excellent agreement between our results and benchmark data for thermal flows ranging from Ra = 103 to 108. Our thermal model captures analogous flow behavior to that of CO2 through fluid-filled porous media, including the transition from diffusive transport to initiation and development of convective fingering.

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.