Dissertations / Theses on the topic 'Dual-Porosity'

In the strive towards reduced fuel consumption and lower emissions, low structural weight is becoming a key factor in the design of advanced vehicle and aerospace structures. Whereas most traditional construction materials are seemingly reaching their limitations, composite materials with their high specific properties offer possibilities to further reduce weight. In high demand structural applications, the quality of the composite material is of utmost importance, requiring the material to be void free and the matrix well distributed as a binder for the load carrying reinforcement. To achieve proper wetting of the fibres, knowledge of the flow resistance of the porous fibre reinforcement is required. It is normally expressed in terms of permeability. Fibre reinforcements in composite materials are normally regarded as a heterogeneous porous media since both fabric and tows are porous but at different length scales. In order to numerically compute the permeability of such media, one of following two approaches can be used. Either filaments are added one-by-one into the modelled geometry (resolved model) or the tows are considered as porous homogenised media. In the latter case expression for the intra-tow permeability is needed. In this thesis, a porous homogenised tow model is benchmarked with a resolved model to the level of refinement possible without being too expensive computationally. Based on this approach, the permeability of complex three- dimensional (3D) textiles is computed utilizing computational fluid dynamics (CFD) analysis. The effect of inter- and intra-tow porosity on the overall permeability of 2D and 3D structures is analysed and discussed in relation to contradictions found in past studies. A clearer picture of the problem is presented, which will be helpful in future modelling and understanding of the permeability of complex structures. In an experimental study, the overall fibre volume fraction as well as the tow compaction are varied and their influence on the permeability is measured. Experimental studies show good agreement with numerical simulations. The interlaminar shear strength of thermoplastic composite materials is studied and the influence of specimen size is examined. Using finite element (FE) analysis it is shown that size effects may be partly due to statistical effects and partly due to the higher number of composite layers in thicker specimens. The effect of processing on the interlaminar delamination toughness of car-bon/polyamide 12 (C/PA12) is studied. It is observed that processing conditions have vital effect on the interlaminar delamination of thermoplastic composites. The mode I crack energy release rate (GIc) of C/PA12 is found to be 15 times higher than for conventional thermoset based composites and 1.5 times higher than for a thermoset composite with stitched reinforcement through the thickness. The best performing C/PA12 composite is manufactured in a hydraulic press equipped with a cold tool, thereby showing potential for both cost and time efficient manufacturing.

QC 20150602

A dual continuum, three-dimensional, isothermal ground-water flow code for unsaturated, fractured, porous media (DCM3D) was calibrated against two test cases; a laboratory block study and data from a monitored field location at the Apache Leap Research Site. Variably saturated water flow in the matrix as well as in the fracture system are described with two separate Richards' equation. Flow between the respective continua is simulated by means of a first order rate equation. Relative permeabilities are calculated using the van Genuchten characteristic relation. The formulation leads to a coupled system of nonlinear partial differential equations which are solved numerically using an integrated finite difference technique. Model calibrations were developed from existing data and supplemented with estimates of parameters not supported by previous research. Estimates included; initial conditions, fracture porosity, fracture van Genuchten parameters (a, m and Or) and the transfer factor. DCM3D proved able to reproduce flow behavior from both test cases. However, given the degrees of freedom, a unique solution was not found. Therefore, an evaluation on the conceptual understanding of flow in each test case was not possible. Sensitivity runs on fracture parameters showed fracture saturated intrinsic permeability and fracture porosity to be the most sensitive parameters relating to travel time. Increases in model complexity dramatically increased run times. Parameters which had the greatest effect on run time where the fracture a and fracture (}r.

The current streamline formulation is limited to single-porosity systems and is then not suitable for application to naturally fractured reservoirs. Describing the fluid transport in naturally fractured reservoirs has been recognized as a main challenge for simulation engineers due to the complicated physics involved. In this work, we generalized the streamline-based simulation to describe the fluid transport in naturally fractured reservoirs. We implemented three types of transfer function: the conventional transfer function (CTF), the diffusion transfer function (DTF), and the empirical transfer function (ETF). We showed that these transfer functions can be implemented easily in the current single-porosity streamline codes. These transfer functions have been added as a source term to the transport equation that describes the saturation evolution along the streamlines. We solved this equation numerically for all types of transfer functions. The numerical solution of the continuity equation with DTF and ETF requires discretizing a convolution term. We derived an analytical solution to the saturation equation with ETF in terms of streamline TOF to validate the numerical solution. We obtain an excellent match between the numerical and the analytical solution. The final stage of our study was to validate our work by comparing our dual-porosity streamline simulator (DPSS) to the commercial dual-porosity simulator, ECLIPSE. The dual-porosity ECLIPSE uses the CTF to describe the interaction between the matrix-blocks and the fracture system. The dual-porosity streamline simulator with CTF showed an excellent match with the dual-porosity ECLIPSE. On the other hand, dual-porosity streamline simulation with DTF and ETF showed a lower recovery than the recovery obtained from the dual-porosity ECLIPSE and the DPSS with CTF. This difference in oil recovery is not due to our formulation, but is related to the theoretical basis on which CTF, DTF, and ETF were derived in the literature. It was beyond the scope of this study to investigate the relative accuracy of each transfer function. We demonstrate that the DPSS is computationally efficient and ideal for large-scale field application. Also, we showed that the DPSS minimizes numerical smearing and grid orientation effects compared to the dual-porosity ECLIPSE.

Streamline-based models have shown great potential in reconciling high resolution geologic models to production data. In this work we extend the streamline-based production data integration technique to naturally fractured reservoirs. We use a dualporosity streamline model for fracture flow simulation by treating the fracture and matrix as separate continua that are connected through a transfer function. Next, we analytically compute the sensitivities that define the relationship between the reservoir properties and the production response in fractured reservoirs. Finally, production data integration is carried out via the Generalized Travel Time inversion (GTT). We also apply the streamline-derived sensitivities in conjunction with a dual porosity finite difference simulator to combine the efficiency of the streamline approach with the versatility of the finite difference approach. This significantly broadens the applicability of the streamlinebased approach in terms of incorporating compressibility effects and complex physics. The number of reservoir parameters to be estimated is commonly orders of magnitude larger than the observation data, leading to non-uniqueness and uncertainty in reservoir parameter estimate. Such uncertainty is passed to reservoir response forecast which needs to be quantified in economic and operational risk analysis. In this work we sample parameter uncertainty using a new two-stage Markov Chain Monte Carlo (MCMC) that is very fast and overcomes much of its current limitations. The computational efficiency comes through a substantial increase in the acceptance rate during MCMC by using a fast linearized approximation to the flow simulation and the likelihood function, the critical link between the reservoir model and production data. The Gradual Deformation Method (GDM) provides a useful framework to preserve geologic structure. Current dynamic data integration methods using GDM are inefficient due to the use of numerical sensitivity calculations which limits the method to deforming two or three models at a time. In this work, we derived streamline-based analytical sensitivities for the GDM that can be obtained from a single simulation run for any number of basis models. The new Generalized Travel Time GDM (GTT-GDM) is highly efficient and achieved a performance close to regular GTT inversion while preserving the geologic structure.

Naturally Fractured Reservoirs (NFR) hold about half of the world’s remaining oil reserves and are typically very heterogeneous. NFR are also important for many other subsurface engineering applications including (nuclear) waste storage, CO2 sequestration, groundwater aquifers, and geothermal energy extraction. They contain faults, fracture corridors, large fractures but also many small-scale fractures as well as a heterogeneous rock matrix. Multi-phase flow in NFR is strongly influenced by this multi-scale heterogeneity. Therefore, accurate conceptual models that reliably quantify fluid flow in NFR are needed. In this thesis, three important contributions are made towards an improved simulation of multi-phase flow processes in NFR. First, the Implicit Pressure Implicit Saturation (IMPIS) method using unstructured grids was implemented to numerically simulate two-phase flow in a Discrete Fracture and Matrix (DFM) model. Second, a Multi-Rate Dual-Porosity (MRDP) model was developed including fracture-matrix transfer functions that are based on analytical solutions for spontaneous imbibition and gravity drainage. Finally, the two approaches were combined to a DFM-MRDP model. This model represents the multi-scale heterogeneity inherent to NFR more accurately by resolving fluid-flow processes in large-scale fractures directly using the DFM model while accounting for complex matrix heterogeneities when modelling fluid exchange between small-scale fractures and rock matrix using the MRDP model.

This dissertation presents the development of a method for quantitative integration of seismic (elastic) anisotropy attributes with reservoir performance data as an aid in characterization of systems of natural fractures in hydrocarbon reservoirs. This new method incorporates stochastic Discrete Feature Network (DFN) fracture modeling techniques, DFN model based fracture system hydraulic property and elastic anisotropy modeling, and non-linear inversion techniques, to achieve numerical integration of production data and seismic attributes for iterative refinement of initial trend and fracture intensity estimates. Although DFN modeling, flow simulation, and elastic anisotropy modeling are in themselves not new technologies, this dissertation represents the first known attempt to integrate advanced models for production performance and elastic anisotropy in fractured reservoirs using a rigorous mathematical inversion. The following new developments are presented: . • Forward modeling and sensitivity analysis of the upscaled hydraulic properties of realistic DFN fracture models through use of effective permeability modeling techniques. . • Forward modeling and sensitivity analysis of azimuthally variant seismic attributes based on the same DFN models. . • Development of a combined production and seismic data objective function and computation of sensitivity coefficients. . • Iterative model-based non-linear inversion of DFN fracture model trend and intensity through minimization of the combined objective function. This new technique is demonstrated on synthetic models with single and multiple fracture sets as well as differing background (host) reservoir hydraulic and elastic properties. Results on these synthetic control models show that, given a well conditioned initial DFN model and good quality field production and seismic observations, the integration procedure results in convergence of both fracture trend and intensity in models with both single and multiple fracture sets. Tests show that for a single fracture set convergence is accelerated when the combined objective function is used as compared to a similar technique using only production data in the objective function. Tests performed on multiple fracture sets show that, without the addition of seismic anisotropy, the model fails to converge. These tests validate the importance of the new process for use in more realistic reservoir models.

This thesis investigates a potential radiochemical method for estimating the capacity of the dual porosity Chalk aquifer to attenuate solutes. Solutes are advected by groundwater flow through fractures, but are slowed and attenuated by molecular diffusion into immobile water in the Chalk matrix. Fracture apertures are a key factor controlling rates of both advection and diffusion. The radiochemical model suggests that apertures may be estimated by comparing radon activity in groundwater with uranium-series isotope activities in the matrix. This estimate would be of great value if both radon release and solute attenuation are dominated by molecular diffusion. The thesis tests the assumptions made in the radiochemical method through a series of laboratory experiments and field observations. This has been achieved by use of • liquid-liquid extraction and luminescence spectrometry to assay Chalk core for uranium; and, • energy-discriminated liquid scintillation to determine both the radium activity of Chalk core and the radon activity in springs and pumped groundwater. The data demonstrate that • the Chalk does not possess a homogeneous distribution of radon precursors, which are dependent on both lithology and disequilibrium within the decay chain; • radon activity of pumped groundwater is highly variable and dependent on both the rate and duration of pumping; and, • spring sources demonstrate variation in radon activity which are not readily explained by the prevailing hydrogeological conditions. At a research site in Berkshire, double-porosity behaviour is shown to dominate solute transport, which can be characterised by an effective diffusion time. However, there is a clear disparity between diffusion times calculated from artificial tracer testing and estimated by the radiochemical method. This suggests that the radiochemical diffusion model is not appropriate in its current form to estimate rates of solute diffusion between fractures and the surrounding Chalk matrix.

L'un des objectifs de l'industrie éolienne est de produire de grandes pièces de structure à moindre coût. Dans ce contexte, la fabrication de pièces composites à partir de renforts quasi unidirectionnels(quasi-UD NCF) avec le procédé d’infusion est compétitive tant sur le plan mécanique que financier. Le procédé d'infusion engendre un phénomène de décompaction dû à la flexibilité de la bâche à vide. De plus les NCF présentent un écoulement à double échelle pendant leur imprégnation. La modélisation des deux phénomènes est souvent réalisée en supposant que la préforme fibreuse est un milieu continu à perméabilité variable. Néanmoins, la perméabilité est influencée par la répartition et la taille des mésopores, qui dépendent de l'état de compaction. Le but de cette thèse est de caractériser expérimentalement l'évolution d'un quasi-UD lors de l’infusion et d’évaluer l'impact de la réorganisation microstructurale sur des quantités macroscopiques d’intérêt, tels que la perméabilité et le temps de remplissage des pièces.Des infusions ont été réalisées à l'intérieur d'un tomographe pour capter l’évolution d’une même microstructure avant et après infusion. Un modèle simplifié a été proposé pour prédire la perméabilité dans le plan et ainsi évaluer l'influence de la réorganisation microstructurelle sur celle-ci. De plus,un outil numérique a été développé pour prendre en compte un écoulement double échelle dans un milieu fibreux déformable bidisperse. L'impact de la décompaction sur le temps de remplissage des pièces a été établi. Une étude mécanique expérimentale du comportement de la mèche tout au long de l’infusion a également été réalisée afin de mieux comprendre le comportement du quasi-UD. Un modèle hyperélastique a finalement été proposé pour prédire le comportement mécanique 3D des mèches pendant la phase de chargement à sec, avant l'infusion
A current aim of wind turbine industries is to produce large structural parts at reduced costs. In this context, manufacture composite blades made of quasi-unidirectional non-crimp fabrics (quasi-UD NCF) using the infusion process is competitive on both mechanical and cost aspects. The infusion process involves an unloading phenomenon due to the vacuum bag flexibility. Additionally, during the impregnation, NCFs exhibit a dual-scale flow. Usual modeling of both phenomena assumes that the fibrous preform is a continuous medium with a varying permeability. Nonetheless, the permeability is affected by the meso-pores size and spatial distribution, which depend on the compaction state. The goal of this thesis is thus to characterize experimentally the flow-induced microstructural evolution of a quasi-UD NCF during the infusion process, and to quantify the impact of thismicrostructural reorganization on relevant macroscopic parameters, such as modelled in-plane permeability as well as computed filling time of parts. In situ infusion process has been conducted inside X-ray Computed Tomography device to capture a dual-scale fibrous microstructure prior and after the infusion process. Additionally, a simplified model has been proposed to predict the in-plane permeability and thus to evaluate the influence of the microstructural reorganization on it. Then, a numerical tool has been developed to account for dual-scale flow in a bidisperse deformable fibrous media. The impact of the dual-scale unloading on themacroscopic filling time of parts has been established. A mechanical investigation of the towbehavior during the infusion process has been additionally carried out experimentally to better understand the quasi-UD NCF behavior. From these results, a hyperelastic model has been proposed to predict the 3D mechanical behavior of tows during the dry loading phase, prior to the infusion process

Le moulage RTM à haute cadence est un procédé de fabrication composite prometteur qui satisfait les exigences de l’industrie automobile pour produire des pièces structurelles complexes avec un temps de cycle court. Cependant, les réductions de temps de cycle sont un véritable défi. Dans ce procédé, une résine est injectée avec mélange en dans la cavité d’un moule contenant un renfort fibreux. Ce flux de résine réactive génère des schémas d’écoulement complexes et des couplages thermo-chimio-rhéologiques forts. En raison de la grande sensibilité de la résine et des temps de cycle serrés, la prédiction de la stratégie d’injection optimale est très difficile et très coûteuse à mener expérimentalement. Le travail réalisé a donc poursuivi deux objectifs: 1. Identifier et quantifier expérimentalement les mécanismes influençant le procédé RTM réactif avec mélange en tête et 2. Développer une méthode de simulation numérique en vue d’introduire les mécanismes identifiés dans le logiciel industriel PAM COMPOSITE développé par ESI Group. L’identification et la quantification des mécanismes ont été réalisées grâce à des investigations expérimentales et numériques. Un nouveau montage expérimental a été développé pour l’étude du mécanisme de stockage de résines intra-mèche grâce à des observations aux échelles macro- et microscopiques. De plus, une méthode numérique a été développée pour simuler l’écoulement réactif de la résine dans des matériaux à simple et à double échelle de porosité. Cette méthode a permis d’étudier les mécanismes locaux difficiles à mesurer expérimentalement et de préparer le transfert vers le logiciel industriel d’ESI
High Speed Resin Transfer Molding (RTM) is a promising composite manufacturing process fitting automotive industry requirements to produce complex structural parts with a perspective of short cycle times. However, cycle time reductions are a real challenge. In this process, a resin mixed on-line with curing agents is injected in the cavity of a mold containing a fibrous reinforcement. This flow of reactive resin generates acomplex flow pattern and strong thermo-chemo rheological couplings. Due to the high sensitivity of the resin cure, and the tight cycle times, prediction of the optimal injection strategy is very difficult and very expensive to conduct experimentally. In this context, two goals where followed in this work: 1. Identify and quantify experimentally the mechanisms, related to the process or to the reinforcement, influencing the reactive RTMprocess with on-line mixing and 2. Develop a numerical simulation method in a view of introducing the identified mechanisms in the industrial software PAMCOMPOSITE developed by ESI Group. Identification and quantification of the mechanisms were realized thanks to experimental investigations and numerical simulations. A new experimental setup has been developed for the investigation of the mechanism of intra-tow resin storage through macro-scale and micro-scale observations. Additionally, a numerical method has been developed to simulate the reactive flow of a resin in single and dual scale porous materials. This method allowed both to investigate local mechanisms difficult to study experimentally and prepare the transfer to the industrial software of ESI

La consommation de ressources pétrolières, épuisables et non renouvelables, conduit à rechercher de nouvelles voies de production pour l’industrie chimique. De plus, la production d’Ordures Ménagères Résiduelles (OMR) continue d’augmenter à l’échelle mondiale. La fermentation acidogène des OMR permet de répondre au double objectif de traiter ces déchets et réduire leur quantité tout en produisant des molécules plateformes biosourcées (acides organiques) d’intérêt pour la chimie.La teneur en solides élevée des OMR et le souci de limiter les coûts de procédé justifient le choix du réacteur à lit percolant ou LBR: il s’agit d’un procédé de fermentation discontinue en voie solide dans lequel une phase liquide est recirculée au sein d’un lit statique de déchets solides. De plus, la mise en œuvre de la fermentation en culture mixte vise à apporter de la diversité microbienne, donc de la robustesse face aux variations de conditions environnementales, et permet de s’affranchir de la nécessité de stériliser le milieu. Par souci de reproductibilité, le principal substrat d’étude a été une reconstitution d’OMR.La première partie de ce travail concerne la compréhension des processus biologiques et chimiques et de leur interaction, au cours de la fermentation acidogène en réacteur batchs séquentiels. L’impact de différents facteurs sur l’hydrolyse et la production de métabolites ont été étudiés: l’ajout d’un inoculum exogène au départ, l’acclimatation de la population microbienne initialement présente vis-à-vis des conditions environnementales, le pH. Il a ainsi été confirmé que le pH joue un rôle clé dans la solubilisation du substrat, la production de métabolites et le spectre de produits. L’analyse de l’évolution des communautés microbiennes a permis de corréler la sélection de certaines familles de bactéries aux performances observées. La fermentation a pu être effectuée avec l’utilisation unique du consortium microbien indigène et l’ajout d’un inoculum extérieur n’a pas contribué à améliorer les performances atteintes. En revanche, la réutilisation de communautés microbiennes, acclimatées aux conditions opératoires par les batchs séquentiels, a été déterminante pour augmenter les productions de métabolites. Ces conclusions ont été comparées à des résultats obtenus à forte teneur en solides.La teneur en solides a une influence considérable sur la réaction de fermentation. Toutefois, sa seule considération n’est pas suffisante car le lit de déchets solides constitue un milieu poreux multiphasique complexe au sein duquel la répartition de l’eau et les phénomènes de transfert sont aussi essentiels. La seconde partie de ce travail visait donc à caractériser le lit de déchets en LBR sur le plan physique et hydrodynamique, en conditions abiotiques. Pour cela, des OMR reconstituées, mais aussi réelles, ont été utilisées. En réalisant des cycles de percolation et drainage avant et après compaction des lits de déchets, la structure des massifs et la distribution de l’eau dans les compartiments ont été déterminées. L’application d’un modèle à double porosité classique pour représenter ces cycles a mis en évidence l’existence d’une fraction d’eau immobile dans la macroporosité. Aussi, un modèle amélioré a été proposé pour reproduire de manière plus adéquate ces dynamiques d’écoulement d’eau dans le massif. Des coefficients de transfert d’eau entre les compartiments ont alors pu être estimés via ce nouveau modèle.Les travaux pluridisciplinaires menés au sein de cette thèse se sont intéressés à deux aspects complémentaires de la fermentation acidogène en LBR et apportent aussi de nouvelles perspectives. Par exemple, la stratégie de recirculation, le contrôle de pH au sein de ce milieu complexe, mais aussi la validation sur des déchets réels sont autant de sujets à explorer afin de pouvoir mettre en œuvre la production optimale et reproductible des molécules plateformes par le procédé étudié, en accord avec les utilisations postérieures visées
The consumption of exhaustible and non-renewable petroleum resources leads to the search for new production routes for the chemical industry. In addition, the global production of Household Solid Waste (HSW) is expected to keep growing. Among a variety of recovery methods, acidogenic fermentation of HSW makes it possible to meet two objectives: treating this waste and reducing its quantity while producing biobased platform molecules of interest for chemical industry such as organic acids.The leach-bed reactor or LBR was chosen due to the high total solids content of HSW and the process cost efficiency. The technology consists of a discontinuous solid-state fermentation process in which a liquid phase is recirculated within a static solid waste bed. Moreover, the use of a mixed culture in fermentation aims to provide microbial diversity, and thus the robustness to face changes in environmental conditions. This strategy also eliminates the need to sterilise the environment. Finally, in this work, the main substrate studied was a reconstitution of HSW.The first part of this work concerns the understanding of the biological and chemical processes and their interaction, during the acidogenic fermentation in sequential batch reactors. The impact of different factors on the hydrolysis of the complex solid substrate and the production of metabolites was studied: the pH, the addition of an exogenous inoculum at start-up and the acclimation of the initial microbial population to the environmental conditions. It was confirmed that pH plays a key role in substrate solubilisation, metabolites production and product spectrum. The analysis of the evolution of microbial communities was assessed, which allowed to correlate the selection of certain families of bacteria with the performances observed. Furthermore, it was feasible to carry out acidogenic fermentation with the unique use of the indigenous microbial consortium and the addition of an external inoculum did not contribute to improve the performances. On the other hand, reusing the microbial communities, acclimated to the operating conditions through the sequential batches, was decisive for increasing the production of metabolites. These conclusions were also compared to results of supplementary experiments obtained at high total solids content.The total solids content has a considerable influence on the fermentation reactions. However, its sole consideration is insufficient because the solid waste bed constitutes a complex multiphase porous medium in which the distribution of water and transfer processes are also essential. Thus, the second part of this work aimed at characterising the physical and hydrodynamic features of the waste bed in a LBR under abiotic conditions. For this, reconstituted HSW as well as real HSW were used. By performing several percolation and drainage cycles, before and after compaction of the waste beds, their physical structure and the distribution of water in their compartments were determined. The application of a classical dual porosity model to represent these cycles helped to demonstrate the existence of a static water fraction in the macroporosity. An improved dual porosity model was proposed to reproduce more adequately the water flow dynamics in the waste bed. Water transfer coefficients between the compartments were then estimated using this new model.The multidisciplinary work carried out in this thesis, focused on two complementary aspects of acidogenic fermentation in a LBR and also brought new perspectives. For instance, the recirculation strategy, the pH control within this complex medium as well as the validation on real waste are all topics to further study in order to implement the optimal and reproducible production of platform molecules by this process, in accordance with the subsequent targeted uses

Besides the advanced knowledge on the fabrication of complex implant biomaterials, modulating the host response is still an unmet challenge in medical applications. The main regulators of this response are the macrophages that can polarize from a pro-inflammatory (M1) phenotype to an anti-inflammatory phenotype (M2) and affect the path of the immune response. Nowadays, strategies to influence macrophage activation for regenerative medicine are being explored to better understand their complex role. Ideally, this modulation would be achieved by altering the physicochemical properties (e.g. stiffness, porosity, topography) of a biomaterial without the addition of exogenous cytokines, growth factors or complicated cell therapies. Thus, this work aimed to create 3D-printed scaffolds with dual porosity and controllable topography, that can tune the foreign body response, fabricated from additive manufacturing and Thermally Inducible Phase Separation (TIPS). Two polymers of Poly(ε-caprolactone-co-lactide) (PCLLA) with different crystallinity were used to fabricate the scaffolds and showed higher porosity and surface roughness than Fused Modelling Deposition (FDM) scaffolds. 3D-TIPS scaffolds, that were rougher and more porous, showed higher cell adhesion and decrease of pro-inflammatory cytokine, TNF-α, comparing to FDM scaffolds. From the in vivo results, scaffolds from the amorphous PCLLA composition showed greater degradation than the more crystalline one, resulting in denser fibrous capsule around the biomaterial. 3D-TIPS scaffolds also showed more cell infiltration inside the fibers suggesting interconnected pores, but FDM scaffolds showed great capacity for cell infiltration by its porosity on the z-axis on the more crystalline polymer. Together, these data indicate a great potential for 3D-TIPS scaffolds to supress pro-inflammatory phenotype comparing with FDM, by increased roughness and porosity.
Além do conhecimento avançado sobre a fabricação de biomateriais complexos, a modulação da resposta do hospedeiro ainda é um desafio em aplicações médicas. Os principais reguladores dessa resposta são os macrófagos que podem polarizar de um fenótipo pró-inflamatório (M1) para um fenótipo anti-inflamatório (M2) e afetar a resposta imune. Atualmente, estratégias para influenciar a ativação de macrófagos para a medicina regenerativa são exploradas para melhor entender o seu papel complexo. Idealmente, esta modulação seria conseguida alterando as propriedades físico-químicas (por exemplo, rigidez, porosidade, topografia) de um biomaterial sem a adição de citocinas exógenas, fatores de crescimento ou terapias celulares complicadas. Assim, este trabalho teve como objetivo criar scaffolds impressos em 3D com porosidade dupla e topografia controlável, que podem ajustar a resposta de corpos estranhos, fabricados a partir de manufatura aditiva e TIPS (Separação de Fases Termicamente Induzida). Dois polímeros de poli(ε-caprolactona-co-lactida) (PCLLA) com diferentes cristalinidades foram utilizados para fabricar os scaffolds e apresentaram maior porosidade e rugosidade superficial do que os scaffolds de FDM (Modelagem por Deposição Fundida). Os scaffolds 3D-TIPS, mais ásperos e porosos, apresentaram maior adesão celular e diminuição da citocina pró-inflamatória, TNF-α, em comparação aos scaffolds de FDM. A partir dos resultados in vivo, scaffolds da composição amorfa de PCLLA mostraram maior degradação do que a mais cristalina, resultando em cápsula fibrosa mais densa a cobrir o biomaterial. Os scaffolds 3D-TIPS também mostraram mais infiltração celular dentro das fibras, sugerindo poros interconectados, mas os scaffolds de FDM mostraram grande capacidade de infiltração celular pela sua porosidade no eixo z no polímero mais cristalino. Por fim, os dados indicam um grande potencial para os scaffolds 3D-TIPS para suprimir o fenótipo pró-inflamatório comparando com a técnica FDM, pelo aumento da rugosidade e porosidade.
Mestrado em Bioquímica

A large percentage of oil and gas reservoirs in the most productive regions such as the Middle East, South America, and Southeast Asia are naturally fractured reservoirs (NFR). The major difference between conventional reservoirs and naturally fractured reservoirs is the discontinuity in media in fractured reservoir due to tectonic activities. These discontinuities cause remarkable difficulties in describing the petrophysical structures and the flow of fluids in the fractured reservoirs. Predicting fluid flow behavior in naturally fractured reservoirs is a challenging area in petroleum engineering. Two classes of models used to describe flow and transport phenomena in fracture reservoirs are discrete and continuum (i.e. dual porosity) models. The discrete model is appealing from a modeling point of view, but the huge computational demand and burden of porting the fractures into the computational grid are its shortcomings. The affect of natural fractures on the permeability anisotropy can be determined by considering distribution and orientation of fractures. Representative fracture permeability, which is a crucial step in the reservoir simulation study, must be calculated based on fracture characteristics. The diagonal representation of permeability, which is customarily used in a dual porosity model, is valid only for the cases where fractures are parallel to one of the principal axes. This assumption cannot adequately describe flow characteristics where there is variation in fracture spacing, length, and orientation. To overcome this shortcoming, the principle of the full permeability tensor in the discrete fracture network can be incorporated into the dual porosity model. Hence, the dual porosity model can retain the real fracture system characteristics. This study was designed to develop a novel approach to integrate dual porosity model and full permeability tensor representation in fractures. A fully implicit, parallel, compositional chemical dual porosity simulator for modeling naturally fractured reservoirs has been developed. The model is capable of simulating large-scale chemical flooding processes. Accurate representation of the fluid exchange between the matrix and fracture and precise representation of the fracture system as an equivalent porous media are the key parameters in utilizing of dual porosity models. The matrix blocks are discretized into both rectangular rings and vertical layers to offer a better resolution of transient flow. The developed model was successfully verified against a chemical flooding simulator called UTCHEM. Results show excellent agreements for a variety of flooding processes. The developed dual porosity model has further been improved by implementing a full permeability tensor representation of fractures. The full permeability feature in the fracture system of a dual porosity model adequately captures the system directionality and heterogeneity. At the same time, the powerful dual porosity concept is inherited. The implementation has been verified by studying water and chemical flooding in cylindrical and spherical reservoirs. It has also been verified against ECLIPSE and FracMan commercial simulators. This study leads to a conclusion that the full permeability tensor representation is essential to accurately simulate fluid flow in heterogeneous and anisotropic fracture systems.
text

A naturally fractured reservoir (NFR) is a reservoir with a connected network of fractures created by natural processes such as diastrophism and volume shrinkage (Ordonez et al. 2001). There are two models to simulate this kind of reservoirs: the discrete fracture model and the dual porosity model. In the dual porosity model, the matrix blocks occupy the same physical space as the fracture network and are identical rectangular parallelepipeds with no direct communication between isotropic and homogeneous matrix blocks. However, each fracture and matrix property is defined separately in the discrete fracture model. Another feature of this thesis is tracer testing. In this process, a chemical or radioactive element is injected to the reservoirs, and then it can be traced using the devices, which are designed to detect the tracers. Tracer tests have several advantages such as determining residual oil saturation, identifying barriers or high permeability zones in reservoirs, and providing the information on flow patterns. Limited number of research studies has been done on performing tracer tests in naturally fractured reservoirs. Also because there is not enough information about the advantages and disadvantages of the discrete fracture and the dual porosity models, researchers and engineers lack the expertise to confidently select either the discrete fracture or the dual porosity models to simulate the different types of NFRs. In this thesis, we compared the oil and water productions, and tracer concentration curves in various reservoir conditions, using both the discrete fracture and the dual porosity models. We used the ECLIPSE, which is a commercial software package in the area of petroleum industry, to model a naturally fractured reservoir. We performed a simple waterflooding with two conservative tracers on the reservoirs. The results presented in each section include the graphs of the oil production rate, water production rate, and tracer concentration. In addition, we presented the oil saturation profiles of a cross-section, which includes the production and injection wells. The results illustrated that both the discrete fracture and the dual porosity models are in good agreement, except for a few special cases. Generally, the oil production using the dual porosity model is more than in the discrete fracture model. The major disadvantage of the dual porosity model is that the fluid distribution in the matrix blocks is changing homogenously during the waterflooding period. In other words, ECLIPSE shows a constant value of the oil and water saturations in each time step for the matrix blocks. However, the dual porosity model is 3 to 4 times faster than the discrete fracture model. In the discrete fracture model, the users have complete control in defining the reservoirs. For example, the fracture aperture, fracture spacing, and fracture porosities can be set by the user. The disadvantage of this model is that millions of grid blocks are needed to model a large reservoir with small fracture spacing.
text

There have been many attempts to use mathematical method in order to characterize shale gas/oil reservoirs with multi-transverse hydraulic fractures horizontal well. Many authors have tried to come up with a suitable and practical mathematical model. To analyze the production data of a shale reservoir correctly, an understanding and choosing the proper mathematical model is required. Therefore, three models (the homogeneous linear flow model, the transient linear dual porosity model, and the fully transient linear triple porosity model) will be studied and compared to provide correct interpretation guidelines for these models. The analytical solutions and interpretation guidelines are developed in this work to interpret the production data of shale reservoirs effectively. Verification and derivation of asymptotic and associated equations from the Laplace space for dual porosity and triple porosity models are performed in order to generate analysis equations. Theories and practical applications of the three models (the homogeneous linear flow model, the dual porosity model, and the triple porosity model) are presented. A simplified triple porosity model with practical analytical solutions is proposed in order to reduce its complexity. This research provides the interpretation guidelines with various analysis equations for different flow periods or different physical properties. From theoretical and field examples of interpretation, the possible errors are presented. Finally, the three models are compared in a production analysis with the assumption of infinite conductivity of hydraulic fractures.

With increase of interest in exploiting shale gas/oil reservoirs with multiple stage fractured horizontal wells, complexity of production analysis and reservoir description have also increased. Different methods and models were used throughout the years to analyze these wells, such as using analytical solutions and simulation techniques. The analytical methods are more popular because they are faster and more accurate. The main objective of this paper is to present and demonstrate type curves for production data analysis of shale gas/oil wells using a Dual Porosity model. Production data of horizontally drilled shale gas/oil wells have been matched with developed type curves which vary with effective parameters. Once a good match is obtained, the well dual porosity parameters can be calculated. A computer program was developed for more simplified matching process and more accurate results. As an objective of this thesis, a type curve analytical method was presented with its application to field data. The results show a good match with the synthetic and field cases. The calculated parameters are close to those used on the synthetic models and field cases.

The advancement of both electronics and instrumentation technology has fostered the development of multi-physics platforms that can probe the earth’s subsurface. Remote, non-destructive testing techniques have led to the increased deployment of electromagnetic waves in sensor technology. Electromagnetic wave techniques are reliable and have the capacity to sense materials and associated properties with minimal perturbation. However, meticulous data analyses and mathematical derivations reveal inconsistencies in some formulations. Thus, revisiting the fundamental physics that underlies both electrical impedance experimental setups and electromagnetic properties are paramount. This study aims to unravel inherent limitations in the understanding of the relationships between electromagnetic and non-electromagnetic properties that are relevant to the characterization of fluids in porous media. These correlations pervade porosity, permeability, specific surface, pore size distribution, tortuosity, fluid discrimination, diffusion coefficient, degree of saturation, viscosity, temperature, phase transformation, miscibility, salinity, and the presence of impurities. The focus is on the assessment of liquids, soils, rocks, and colloids using broad spectral frequency complex permittivity, conductivity, magnetic permeability, and nuclear magnetic resonance relaxometry. Broadband electrical properties measurement for saturated porous media can provide multiple physical phenomena: Ohmic conduction, electrode polarizations, Maxwell-Wagner spatial polarizations, rotational, and segmental polarizations. Liquids dominate the electromagnetic signatures in porous media as dry minerals are inherently non-polar and non-conductive. Results reveal that voltage drops due to the discontinuity of charge-carrier at the electrode-electrolyte interface named electrode polarization inherently affect the low-frequency electrical measurements both in two- and four-probe configurations. Rotational polarizations that occur in MHz-GHz ranges are defined by the electrical dipole moment and effective molecular volume. Both viscosity and effective molecular volume govern the NMR transverse relaxation time. An engineered soil suspension with ferromagnetic inclusions exhibits excellent characteristics for drilling fluid application. Overall, the study highlights the complementary nature of conductivity, permittivity, and NMR relaxation for the advanced characterization of fluid saturated geomaterials.

Different methods have been proposed for history matching production of shale gas/oil wells which are drilled horizontally and usually hydraulically fractured with multiple stages. These methods are simulation, analytical models, and empirical equations. It has been well known that among the methods listed above, analytical models are more favorable in application to field data for two reasons. First, analytical solutions are faster than simulation, and second, they are more rigorous than empirical equations. Production behavior of horizontally drilled shale gas/oil wells has never been completely matched with the models which are described in this thesis. For shale gas wells, correction due to adsorption is explained with derived equations. The algorithm which is used for history matching and forecasting is explained in detail with a computer program as an implementation of it that is written in Excel's VBA. As an objective of this research, robust method is presented with a computer program which is applied to field data. The method presented in this thesis is applied to analyze the production performance of gas wells from Barnett, Woodford, and Fayetteville shales. It is shown that the method works well to understand reservoir description and predict future performance of shale gas wells. Moreover, synthetic shale oil well also was used to validate application of the method to oil wells. Given the huge unconventional resource potential and increasing energy demand in the world, the method described in this thesis will be the "game changing" technology to understand the reservoir properties and make future predictions in short period of time.

Many hydraulically fractured shale gas horizontal wells in the Barnett shale have been observed to exhibit transient linear behavior. This transient linear behavior is characterized by a one-half slope on a log-log plot of rate against time. This transient linear flow regime is believed to be caused by transient drainage of low permeability matrix blocks into adjoining fractures. This transient flow regime is the only flow regime available for analysis in many wells. The hydraulically fractured shale gas reservoir system was described in this work by a linear dual porosity model. This consisted of a bounded rectangular reservoir with slab matrix blocks draining into adjoining fractures and subsequently to a horizontal well in the centre. The horizontal well fully penetrates the rectangular reservoir. Convergence skin is incorporated into the linear model to account for the presence of the horizontal wellbore. Five flow regions were identified with this model. Region 1 is due to transient flow only in the fractures. Region 2 is bilinear flow and occurs when the matrix drainage begins simultaneously with the transient flow in the fractures. Region 3 is the response for a homogeneous reservoir. Region 4 is dominated by transient matrix drainage and is the transient flow regime of interest. Region 5 is the boundary dominated transient response. New working equations were developed and presented for analysis of Regions 1 to 4. No equation was presented for Region 5 as it requires a combination of material balance and productivity index equations beyond the scope of this work. It is concluded that the transient linear region observed in field data occurs in Region 4 – drainage of the matrix. A procedure is presented for analysis. The only parameter that can be determined with available data is the matrix drainage area, Acm. It was also demonstrated in this work that the effect of skin under constant rate and constant bottomhole pressure conditions is not similar for a linear reservoir. The constant rate case is the usual parallel lines with an offset but the constant bottomhole pressure shows a gradual diminishing effect of skin. A new analytical equation was presented to describe the constant bottomhole pressure effect of skin in a linear reservoir. It was also demonstrated that different shape factor formulations (Warren and Root, Zimmerman and Kazemi) result in similar Region 4 transient linear response provided that the appropriate f(s) modifications consistent with lAc calculations are conducted. It was also demonstrated that different matrix geometry exhibit the same Region 4 transient linear response when the area-volume ratios are similar.

In order to understand the complex fracture network that controls water movement in Sherrod Area of Spraberry Field in West Texas and to better manage the on-going waterflood performance, a field scale inter-well tracer test was implemented. This test presents the largest inter-well tracer test in naturally fractured reservoirs reported in the industry and includes the injection of 13 different tracers and sampling of 110 producers in an area covering 6533 acres. Sherrod tracer test generated a total of 598 tracer responses from 51 out of the 110 sampled producers. Tracer responses showed a wide range of velocities from 14 ft/day to ultra-high velocities exceeding 10,000 ft/day with same-day tracer breakthrough. Re-injection of produced water has caused the tracers to be re-injected and added an additional challenge to diagnose and distinguish tracer responses affected by water recycling. Historical performance of the field showed simultaneous water breakthrough of a large number of wells covering entire Sherrod area. This research investigate analytical, numerical, and inversion modeling approaches in order to categorize, history match, and connect tracer responses with water-cut responses with the objective to construct multiple fracture realizations based entirely on water-cut and tracers‟ profiles. In addition, the research highlight best practices in the design of inter-well tracer tests in naturally fractured reservoirs through lessons learned from Sherrod Area. The large number of tracer responses from Sherrod case presents a case of naturally fractured reservoir characterization entirely based on dynamic data. Results indicates that tracer responses could be categorized based on statistical analysis of tracer recoveries of all pairs of injectors and producers with each category showing distinguishing behavior in tracers‟ movement and breakthrough time. In addition, it showed that tracer and water-cut responses in the field are dominantly controlled by the fracture system revealing minimum information about the matrix system. Numerical simulation studies showed limitation in dual porosity formulation/solvers to model tracer velocities exceeding 2200 ft/day. Inversion modeling using Gradzone Analysis showed that east and north-west of Sherrod have significantly lower pore volume compared to south-west.

Research Doctorate - Doctor of Philosophy (PhD)
This thesis is dedicated to the modelling of multiphase flows in naturally fractured rocks and, in particular, to the recovery of methane, or reversely to the storage of carbon dioxide, in coalbeds. In this context, some hydro-mechanical couplings can likely affect the permeability of the reservoir. On the one hand, the increase in effective stress after the reservoir depletion tends to decrease the permeability. On the other hand, the matrix shrinkage following gas desorption tends to increase the permeability. These phenomena are highlighted with some experimental tests carried out in laboratory. Some numerical models are developed in this thesis to properly take into account the permeability evolution during the gas production/storage. As coal is rarely dry in situ, constitutive models are developed for unsaturated conditions. These models are implemented in the finite element code Lagamine.

The primary objective was to predict the relative storage capacity of carbonate rocks relevant for carbon dioxide sequestration. To achieve this, a detailed pore scale characterization of model carbonate rocks, Indiana Limestone and Pink Dolomite, was conducted utilizing micro-computed tomography (microCT) data using pore network modeling and invasion percolation simulations. For the first time in literature, Pink Dolomite’s pore space characteristics were analyzed. A secondary objective was to compare thresholding techniques as applied to carbonates which exhibit dual porosity (porosity at multiple length scales). The analysis showed the sensitivity of existing methods to the thresholding technique, imaging method and material. Overall, the contributions of this work provide an assessment of two carbonates relevant for carbon capture and storage at the pore scale; and a preliminary assessment into thresholding dual porosity carbonates.

Lithium-ion battery is attractive for various applications because of its high energy density. The performance of Li-ion battery is influenced by several properties of the electrode materials such as particle size, surface area, ionic and electronic conductivity, etc. Porosity is another important property of the electrode material, which influences the performance. Pores can allow the electrolyte to creep inside the particles and also facilitate volume expansion/contraction arising from intercalation/deintercalation of Li+ ions. Additionally, the rate capability and cycle-life can be enhanced. The following porous electrode materials are investigated. Poorly crystalline porous -MnO2 is synthesized by hydrothermal route from a neutral aqueous solution of KMnO4 at 180 oC and the reaction time of 24 h. On heating, there is a decrease in BET surface area and also a change in morphology from nanopetals to clusters of nanorods. As prepared MnO2 delivers a high discharge specific capacity of 275 mAh g-1 at a specific current of 40 mA g-1 (C/5 rate). Lithium rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template. It has a well crystalline structure with a broadly distributed mesoporosity but low surface area. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g-1 is obtained at a discharge current of 30 mA g-1. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g-1 at a discharge current density of 30 mA g-1. Solid solutions of Li2MnO3 and LiMO2 (M=Mn, Ni, Co, Fe and their composites) are more attractive positive electrode materials because of its high capacity >200 mAh g-1.The solid solutions are prepared by microemulsion and polymer template route, which results in porous products. All the solid solution samples exhibit high discharge capacities with high rate capability. Porous flower-like α-Fe2O3 nanostructures is synthesized by ethylene glycol mediated iron alkoxide as an intermediate and heated at different temperatures from 300 to 700 oC. The α-Fe2O3 samples possess porosity with high surface area and deliver discharge capacity values of 1063, 1168, 1183, 1152 and 968 mAh g-1 at a specific current of 50 mA g-1 when prepared at 300, 400, 500, 600 and 700 oC, respectively. Partially exfoliated and reduced graphene oxide (PE-RGO) is prepared by thermal exfoliation of graphite oxide (GO) under normal air atmosphere at 200-500 oC. Discharge capacity values of 771, 832, 1074 and 823 mAh g -1 are obtained with current density of 30 mA g-1 at 1st cycle for PE-RGO samples prepared at 200, 300, 400 and 500 oC, respectively. The electrochemical performance improves on increasing of exfoliation temperature, which is attributed to an increase in surface area. The high rate capability is attributed to porous nature of the material. Results of these studies are presented and discussed in the thesis.