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.

Ο στόχος της παρούσας εργασίας είναι η περαιτέρω κατανόηση και ποσοτική σύνδεση φαινομένων μεταφοράς που λαμβάνουν χώρα σε πορώδη μέσα με τα αντίστοιχα φαινόμενα στην κλίμακα λίγων πόρων. Η επέκταση των αποτελεσμάτων από την κλίμακα πόρου στην κλίμακα του πορώδους μέσου δεν είναι προφανής και για το λόγο αυτό η τοπολογία και μορφολογία της πορώδους δομής αντιμετωπίζονται εδώ με δίκτυα πόρων, με έμφαση στα φαινόμενα που λαμβάνουν χώρα στις διασταυρώσεις, αλλά και με ψηφιακές αναπαραστάσεις της δομής με βάση μικροφωτογραφίες δείγματος του υλικού. Συγκεκριμένα, στην εργασία αυτή εξετάζεται η διασπορά μορίων διαλυμένης ουσίας σε δίκτυα πόρων, παρουσιάζεται μία καινούργια τεχνική ανακατασκευής ανομοιογενών πορωδών υλικών και αναπτύσσεται μια μέθοδος προσομοίωσης της ροής αερίων δια μέσου ανακατασκευασμένων πορωδών υλικών στη μεταβατική περιοχή ροής όπου η μέση ελεύθερη διαδρομή των μορίων ενός αερίου είναι συγκρίσιμη με το μέγεθος των πόρων οπότε και παύει να ισχύει η συνήθης παραδοχή του συνεχούς. Η επίδραση της ανάμειξης μέσα σε πόρους ή στις διασταυρώσεις πόρων/ρωγμών στη διασπορά μορίων διαλυμένης ουσίας σε πορώδη μέσα ερευνήθηκε μέσα από την ανάπτυξη και χρήση διαφορετικών τεχνικών προσομοίωσης με έμφαση στις λεπτομέρειες της ροής και της μεταφοράς μάζας στην περιοχή της διασταύρωσης. Βρέθηκε ότι μία νέα μέθοδος τυχαίου περιπάτου αναπαράγει με καλή ακρίβεια το συντελεστή διασποράς σε χαμηλές και μεσαίες τιμές του Peclet, χάρη στο γεγονός ότι λαμβάνει υπ’ όψη την ανάντι της ροής κίνηση των σωματιδίων και τους διαφορετικούς χρόνους παραμονής μέσα σε κάθε κλάδο. Παράλληλα αναπτύχθηκε μία καινοτόμος μέθοδος ανακατασκευής πορωδών μέσων. Η τεχνική στηρίζεται στο διφασικό πρότυπο δικτύου Boltzmann, το οποίο περιγράφει την εξέλιξη συστημάτων υγρού-αερίου υπό την επίδραση της διεπιφανειακής τάσης. Ο μηχανισμός αυτός οδηγεί στη δημιουργία συσχετισμένων δομών, όπου τόσο η μορφολογία του πορώδους μέσου όσο και ο βαθμός συσχέτισής του καθορίζονται από τις λειτουργικές παραμέτρους του προτύπου. Η τεχνική εφαρμόστηκε επιτυχώς σε πραγματικό δείγμα εδάφους με αφετηρία την πληροφορία που δίνεται από μία μικροφωτογραφία μίας στατιστικά χαρακτηριστικής τομής του. Τέλος, μελετήθηκε η ροή αερίων σε πορώδη μέσα, σε πεπερασμένους αριθμούς Knudsen, όπου η μέση διάμετρος των πόρων είναι της ίδιας τάξης με τη μέση ελευθέρα διαδρομή των μορίων του αερίου. Η μελέτη έγινε με τη μεσοσκοπική μέθοδο DSMC. Ο έλεγχος της αξιοπιστίας της μεθόδου και της παρούσας υλοποίησής της έγινε μέσω της μελέτης της ισοθερμοκρασιακής ροής αερίου μεταξύ παραλλήλων πλακών. Παράλληλα υπολογίστηκε το δυναμικό ιξώδες αερίου σε συνθήκες υψηλής αραίωσης και παρουσιάστηκε η εξάρτησή του από τον αριθμό Knudsen. Βρέθηκε ότι τα αποτελέσματα προσεγγίζονται ικανοποιητικά από μία αναλυτική έκφραση τύπου Bosanquet που συσχετίζει το αποτελεσματικό ιξώδες με την τιμή του στο όριο του συνεχούς και με τον αριθμό Knudsen. Επιπρόσθετα μελετήθηκε για πρώτη φορά με τη μέθοδο DMSC η ροή αερίων σε υπολογιστικά ανακατασκευασμένες πορώδεις δομές. Επιβεβαιώθηκε το φαινόμενο του Klinkenberg και η γραμμική εξάρτηση του συντελεστή διαπερατότητας από την αντίστροφη πίεση. Τέλος χρησιμοποιήθηκε μια διαφορετική προσέγγιση στο πρόβλημα υπολογισμού της ροής στη μεταβατική περιοχή μέσω ανάπτυξης προτύπου δικτύου Boltzmann, κατάλληλα τροποποιημένου για ροές σε συνθήκες αραίωσης. Το πρότυπο δοκιμάστηκε τόσο στην περίπτωση ροής μεταξύ παραλλήλων πλακών όσο και σε ροή σε πορώδη μέσα όπου η συμφωνία με τη μέθοδο DSMC βρέθηκε πολύ ικανοποιητική. / The aim of the present study is the further understanding and quantification of transport phenomena in porous media and their connection with the phenomena in the scale of a few pores. The extension of the results from the pore-scale to the scale of the porous medium is not obvious and for this reason the representation of the porous medium is treated both with pore-networks and digital reconstruction. Specifically, in this study it is examined the dispersion of molecules of a solute in porous networks, a new reconstruction technique is presented for heterogeneous granular materials and also a methodology is developed for the study of gas flow in reconstructed porous media in the transient regime, where the mean free path of the gas molecules is comparable with the characteristic length of the pores and thus the continuum description is no longer valid. The effect of the mixing in the pores or the junctions of the pores on the dispersion of molecules of a solute in porous media is examined through various simulation techniques with emphasis on the details of the flow and mass transport in the area of the junction. It was found that a new random-walk technique is reproducing with good accuracy the dispersion coefficient for low and average values of the Peclet number, due to the fact that it takes into account the backwards, with respect to the main direction of the flow, movement of the molecules and the different residence time in each branch. Furthermore, a new reconstruction technique was developed for porous media. The technique is based on 2-phase lattice Boltzmann model, which describes the evolution of a gas-liquid system under the influence of the surface tension. This mechanism leads to the creation of correlated structures, where the morphology of the porous medium and the correlation factor are determined by the operating parameters of the model. The technique was applied successfully for the reconstruction of a real soil sample, starting from the information that is solely given from a microphotograph of a statistically adequate section of the material. Finally, the gas flow through porous media was examined at moderate Knudsen numbers, where the mean diameter of the pores is of the same order of magnitude with the mean free path of the gas molecules. The study was done mainly with the mesoscopic DSMC technique. The credibility of the technique was examined through the study of the isothermal gas flow through parallel plates. Additionally, the dynamic viscosity of a gas under rarefaction conditions was calculated and its dependence on the Knudsen number was shown. It was found that the results are approximated satisfactorily with an analytical Bosanquet-type equation that relates the effective viscosity with its value at the continuum limit and with the Knudsen number. Furthermore, it was studied for the first time with the DSMC method the gas flow through reconstructed porous media. The Klinkenberg effect was confirmed and the linear dependence of the permeability coefficient on the inverse pressure was shown. Finally an alternative approach was used for the calculation of gas flow though porous media in the transient regime through the development of a lattice Boltzmann model suitably modified for rarefied gas flows. The model was tested for the case of flow through parallel plates as well as for the case of flow through porous media and the agreement with the DSMC method was very satisfactory.

Le contrôle thermique des composants électroniques embarqués dans les engins spatiaux est souvent assuré par des boucles fluides diphasiques à pompage capillaire (Loop Heat Pipe (LHP) ou Capillary Pumped Loop (CPL)). La présente étude est centrée sur les évaporateurs des LHP. Ils sont composés principalement d’un bâti métallique, d’une mèche poreuse et de cannelures. Le milieu poreux est initialement saturé en liquide. La charge thermique à évacuer est appliquée sur le bâti entraînant la vaporisation du liquide au sein de la mèche. La vapeur est ensuite récoltée au sein des cannelures pour être évacuée. L’étude est effectuée sur une cellule unitaire de l’évaporateur. Dans le but d’étudier les transferts de masse et de chaleur, un modèle de réseau de pores 3D dit mixte a été développé. Les champs de pression et de température sont calculés à partir des équations macroscopiques tandis que la capillarité est gérée à l’aide d’une approche réseau de pore classique. L’un des avantages d’une telle formulation est de pouvoir accéder à la répartition des phases liquide et vapeur au sein de l’espace poral du milieu poreux. Il a ainsi été mis en évidence qu’une zone diphasique (zone où le liquide et la vapeur coexistent) se met en place pour une large gamme de flux lorsque la vapeur apparait dans la structure capillaire. Cette zone diphasique est localisée sous le bâti métallique et est corrélée avec les meilleures performances thermiques de l’évaporateur. Cette observation diffère fortement de l’hypothèse souvent considérée de la présence d’une zone sèche dans cette région. Trois positions différentes de cannelures ont été étudiées. Il a ainsi pu être mis en évidence que la plus large gamme de flux, pour laquelle les performances de l’évaporateur sont les meilleures, est obtenue lorsque les cannelures sont usinées à la surface extérieure de la mèche. Toujours dans le but d’améliorer les performances thermiques de l’évaporateur, une étude paramétrique a été menée pour mettre en évidence les paramètres qui influencent positivement la conductance de l’évaporateur. Finalement, l’étude de l’influence d’une mèche biporeuse/bidispersée, c’est-à-dire d’un milieu poreux caractérisé par deux tailles de pores/liens différentes, a été menée. La distribution des phases liquide et vapeur au sein de la structure capillaire bidispersée est différente de celle d’un milieu mono-poreux du fait des chemins préférentiels créés par les larges pores. Par ailleurs, l’analyse thermique a montré qu’un tel milieu poreux permet de réduire considérablement la température du bâti ainsi que d’augmenter les performances thermiques de l’évaporateur. Un deuxième modèle basé sur une approche continue a été développé. Cette méthode utilise l’algorithme IMPES (IMplicit Pressure Explicit Saturation) et est couplé à la résolution du champ de température avec changement de phase. Ce type de résolution permet d’accéder à un champ de saturation. Les résultats ainsi obtenus sont en bon accord avec ceux prédits par le modèle réseau de pores mixte. Le modèle continu, moins gourmand en temps de calcul, permet d’envisager des simulations sur une plus grande partie de l’évaporateur. / The thermal control of electronic devices embedded in spacecraft is often carried out by capillary twophase loop systems (Loop Heat Pipe (LHP) or Capillary Pumped Loop (CPL)). This thesis focuses on the LHP evaporators. They mostly consist of a metallic casing, a porous wick and vapour grooves. The porous medium is initially saturated with liquid. The heat load is applied at the external surface of the casing inducing the vaporisation of the liquid within the wick. The vapour is then evacuated thanks to the vapour grooves. A unit cell of the evaporator is studied and corresponds to our computational domain. A so-called 3D mixed pore network model has been developed in order to study the heat and mass transfers. Pressure and temperature fields are computed from macroscopic equations, while the capillarity is managed using the classical pore network approach. The main advantage of such formulation is to obtain the liquid-vapour phase distribution within the porous medium pore space. The work highlights that a two-phase zone (characterized by the coexistence of the liquid and the vapour) exists for a large range of fluxes when vaporisation takes place within the capillary structure. This twophase zone is located right under the casing and is positively correlated with the best evaporator thermal performances. This result differs from the often made assumption of a dry region under the casing. Three different groove locations are tested. This investigation highlights that evaporator thermal performances are the best over a large range of fluxes for grooves manufactured at the external surface of the wick. In complement, a parametric study is performed to highlight parameters which impact positively the evaporator thermal performances. Finally, a biporous/bidispersed wick, i.e. a wick with a bimodal pore/throat size distribution, is studied. The liquidvapour phase distribution within the capillary structure is different from the one for a monoporous structure due to preferential vapour paths created by the large throats and pores-network. Moreover, the thermal analysis shows that such a porous medium permits to reduce considerably the evaporator wall temperature and to increase the evaporator thermal performances. A second model is developed based on a continuum approach. This method uses the IMPES (IMplicit Pressure Explicit Saturation) algorithm coupled with the heat transfer with phase change. Results are in good agreement with those predicted by the mixed pore network model. The continuum model, requiring less computing time, should allow considering larger sub domains of the evaporator.

[pt] A produtividade de poços produtores de gás, que operam com pressões de fundo inferiores à pressão de orvalho, é afetada pelo aparecimento da saturação de líquido em seus entornos. Para entender esse fenômeno, conhecido como bloqueio por condensado, os simuladores em escala de poros são ferramentas úteis na investigação dos parâmetros que influenciam na quantidade e na distribuição da saturação de condensado, assim como seus efeitos na redução do fluxo de gás. Esse trabalho apresenta um modelo de rede de capilares composicional e isotérmico para o estudo do escoamento de gás retrógrado em meios porosos. Forças capilares e gravitacionais não foram consideradas. O escoamento monofásico é comutado para bifásico de padrão anular quando a pressão e a composição do fluido atingem um critério de estabilidade. O método de Newton é aplicado para resolver as equações de fluxo e consistência dos volumes e calcular o transporte de cada um dos componentes ao longo da rede. As propriedades do fluido e o comportamento do escoamento foram testadas contra os resultados de um simulador termodinâmico comercial e soluções analíticas, respectivamente. Após validação, o simulador foi utilizado para obter curvas de permeabilidade relativa gás-líquido através da despressurização de uma rede 2D e alguns resultados são discutidos. / [en] Gas well deliverability in retrograde gas reservoirs is affected by the appearance of liquid saturation around the wellbore when the bottom-hole pressure is below the dew point. Pore-scale simulators are used to model this phenomenon, known as condensate blockage, and to investigate parameters that ifluence the amount and the distribution of condensate saturation, as well as how it chokes the gas flow. Here, a fully-implicit isothermal compositional pore-scale network model is presented for retrograde gas flow in porous media. Capillary and gravitational forces are neglected. The model shifts from single-phase flow to annular flow regime when the pressure and the fluid composition reach a stability criteria. Newton s method is applied on flow and volume consistency equations to calculate the transport of each component through the network. Fluid properties and flow behavior were tested against a commercial thermodynamic simulator and analytical solutions respectively. After validation, the simulator was used to predict gas-liquid relative permeability from a depletion process in a 2D network and some results are discussed.

En vue de contrôler les émissions de gaz à effet de serre, il est envisagé d’injecter du CO2 dans des réservoirs géologiques. Or le CO2 n'est pas un gaz inerte. En modifiant la composition chimique de l'eau in situ, il est à l'origine d'interactions roche/fluide. Ces réactions géochimiques impactent les propriétés d'écoulement. Aussi, pour s'assurer de la viabilité et de la pérennité du stockage, les opérateurs ont besoin de simulations tenant compte de ces écoulements réactifs. Cependant les paramètres de l'équation macroscopique de transport utilisée sont affectés par les réactions surfaciques. Or, ces spécificités dues au transfert de masse ne sont pas prises en compte actuellement. De même, la loi perméabilité-porosité (K-F) n’est estimée que semi-empiriquement. Le but de cette thèse a été de développer une méthode pour obtenir les coefficients macroscopiques précédents et les relations K-F, en résolvant les équations gouvernant les phénomènes à l'échelle du pore. Pour ce faire, nous avons utilisé l'approche réseau de pores. L'avantage du modèle réseau est qu'il prend en compte explicitement la structure tout en conceptualisant cette dernière à un ensemble de pores et de canaux à la morphologie simplifiée (sphères, cylindres). L'étude est basée sur deux changements d'échelles successifs : du local au pore, puis du pore à la carotte. Le problème de transport réactif est résolu pour des éléments basiques, analytiquement ou numériquement. Puis, en faisant appel aux solutions précédemment trouvées, le transport réactif est traité sur l'ensemble du réseau. Notre model fut validé par des observations sur micromodèles, puis à l'aide d'une expérience d'altération acide / The geological storage of CO2 is considered as an attractive option to reduce the greenhouse gas emissions in the atmosphere. CO2 is not an inert gas, however. Its dissolution in brine forms a weak acid that has the potential to react with the host rock formation. The induced pores structure modification impacts the flow properties. Thus, to ensure the viability and sustainability of CO2 storage, operators need simulations that take into account the specificities of reactive transport. However, the macroscopic coefficients of the reactive transport equation are modified from the values of an inert tracer by surface reactions. These specificities due to mass transfer are currently not considered. Similarly, the permeability-porosity (K-F) relationship is only estimated semi-empirically. The aim of this thesis was to develop a method to obtain the macroscopic coefficients and the K-F laws, by solving the equations governing the pore-scale phenomena. To do this, we used the Pore Network Modelling approach (PNM). The advantage of the PNM is that it explicitly takes into account the pore structure, while conceptualizing the latter to a set of pores and throats whose morphology is simplified into spheres or cylinders for instance. The study is based into two successive upscalings: from local-scale to pore-scale, then from pore-scale to core-scale. The reactive transport problem is solved for basic elements, analytically or numerically. Then, using the solutions previously found at the pore scale, the reactive transport phenomena are treated throughout the network. Our model was validated by observations on micromodels and by a comparison with an acid-induced alteration experiment

Dans ce travail, nous nous intéressons à la dynamique de croissance d'une poche de vapeur par vaporisation en milieu poreux, en relation avec l'analyse des transferts couplés de masse et de chaleur dans les mèches poreuses des boucles fluides diphasiques à pompage capillaire. Nous proposons un modèle pour les régimes transitoires, régimes encore très mal compris en dépit de leur grande importance pratique (phase de démarrage, variations de puissance, etc.). Une approche de type "réseau de pores" est adoptée et permet de prédire la distribution des phases à l'échelle de l'espace des pores. Dans une étape préliminaire, une étude spécifique de drainage (déplacement d'un fluide mouillant par un fluide non mouillant) par pressurisation du fluide envahisseur est abordée. Cette étape, nécessaire au développement et au test d'un algorithme de croissance de poche de gaz, permet de valider le modèle hydrodynamique quantitativement par une étude expérimentale dédiée. Il est mis en évidence le rôle des films liquides et de la compressibilité du gaz. Le modèle est ensuite complété par l'ajout des transferts thermiques et du changement de phase. Ici encore, une étude expérimentale dédiée est proposée, afin de valider l'outil numérique mis en place. Enfin, un ultime ajout au modèle permet de prendre en compte les phénomènes particuliers liés à l'imbibition (déplacement d'un fluide non mouillant par un fluide mouillant). Des résultats statistiques concernant la réponse dynamique d'une poche de vapeur à l'application d'une densité de puissance sont présentés, ainsi que certaines situations oscillantes dans la mèche poreuse. Nous finissons par discuter de l'influence du re-mouillage de la mèche poreuse, phénomène qui entraîne une hystérésis significative. / We study the dynamic of a vapour pocket growing by vaporisation in a porous medium, in relation with the analysis of coupled heat and mass transfers in the porous wick of loop heat pipes (LHP). We propose a model for transient modes, which are still poorly understood in spite of their importance (start-ups, power transitions, etc.). This work is based on a pore network approach enabling us to predict the phase distribution at the pore space scale. In a preliminary step, a study of drainage (displacement of a wetting fluid by a non wetting one) by pressurisation of the invading fluid is performed. This step is necessary for the development and the test of the vapour pocket growing algorithm. A quantitative validation of the hydro-dynamical model is obtained thanks to a dedicated experimental study. The influence of liquid films as well as gas compressibility is investigated. Our model is then improved to deal with heat transfer and phase change. Again, a dedicated experimental study is performed in order to validate the numerical tool. The model is finally improved a last time to deal with the effects due to imbibition mechanisms (displacement of a non wetting fluid by a wetting one). Statistical results concerning the dynamic response of a vapour pocket to the application of a power density are presented, andsome specific oscillating situations in the wick are identified. We finish discussing the influence of the re- etting of the porous wick, a phenomenon which induces a significant hysteresis effect.

[pt] Uma das características mais relevantes nos aglomerados de minério de ferro é a sua porosidade, que impacta fortemente no desempenho desses materiais nos processos siderúrgicos. O desempenho é diretamente dependente da existência de uma rede porosa que permite o fluxo de gases pelo interior desses aglomerados sem comprometer sua integridade física. Neste trabalho, amostras de diferentes tipos de aglomerados de minério de ferro foram caracterizadas com o auxílio de técnicas de microtomografia computadorizada de raios X (microCT), processamento digital de imagens e modelagem de rede de poros (PNM). Com isso, a influência da microestrutura desses aglomerados na variação da sua porosidade e permeabilidade foi avaliada. O uso de microCT permitiu uma visualização 3D da estrutura dos aglomerados, permitindo realizar uma análise da estrutura interna das amostras para a discriminação do espaço poroso. O pixel size ideal foi estipulado por meio de diversas capturas com resoluções diferentes. A PNM foi utilizada para realizar a simulação da permeabilidade absoluta das amostras, correlacionando com a porosidade, conectividade dos poros e diâmetro de poros e conexões. Foi realizada uma variação de mais ou menos 5 tons de cinza nos limiares de segmentação para estipular a sensibilidade do impacto desse parâmetro nos resultados da modelagem. Os dois aglomerados apresentaram porosidade parecida, em torno de 20 por cento. Os resultados para piores resoluções apresentaram uma inconsistência, em muitos casos não possuindo sequer permeabilidade. As imagens adquiridas com um tamanho de voxel de 2 micrômetros resultaram em cálculos consistentes de permeabilidade, em torno de 0,4 a 2,4 mD para os briquetes e 0,03 a 1,6 mD para as pelotas, sugerindo que os briquetes são levemente mais permeáveis. A variação do limiar de segmentação dos poros teve forte impacto nos resultados das modelagens, influenciando diretamente no valor do cálculo da permeabilidade absoluta. / [en] One of the most relevant features of iron ore agglomerates is their porosity, which strongly impacts the performance of these materials in steelmaking processes. Performance is directly dependent on the existence of a porous network that allows gas flow through the interior of these agglomerates without compromising their physical integrity. This study characterized samples of different iron ore agglomerates using X-ray microcomputed tomography (microCT), digital image processing, and pore network modeling (PNM). The influence of the microstructure of these agglomerates on the variation of their porosity and permeability was evaluated. MicroCT enabled a 3D visualization of the agglomerate structure, allowing for an analysis of the internal structure of the samples to discriminate the porous space. The ideal pixel size was determined through various captures at different resolutions. PNM was used to simulate the absolute permeability of the samples, correlating it with porosity, pore connectivity, and pore and connection diameter. A variation of more or less 5 gray tones in the segmentation thresholds was performed to determine the sensitivity of this parameter s impact on the modeling results. The two agglomerates had similar porosity of around 20 percent. The results for lower resolutions showed inconsistency, with many cases lacking permeability altogether. Images acquired with a pixel size of 2 micrometers resulted in consistent permeability calculations, ranging from 0.4 to 2.4 mD for briquettes and 0.03 to 1.6 mD for pellets, indicating that briquettes are slightly more permeable. The variation of pore segmentation threshold had a strong impact on the modeling results, directly influencing the value of the absolute permeability calculation.

We theoretically and experimentally investigate the impact of pore space structure, wettability, and surface roughness on the displacement front, trapping, and sweeping efficiency at low capillary numbers. The microstructure of (i) 2D geologically-realistic media (2D natural sand and sandstone), (ii) a topological 3D-2D-transformation (2D sand analog), and (iii) geometrically representative media (Delaunay Triangulation) were studied over a wide range of wettability from water-wet to oil-wet systems provided by using various fluid-pairs. We observed the transition (compact to fractal) in the displacement front caused by local instabilities identified by Cieplak and Robbins. The trapping efficiency of 2D natural microstructures showed a non-monotonous dependency on wettability, whereas a crossover from no trapping to maximal trapping was observed in 2D patterns of circular grains. For the first time, we compared identical experimental microstructures with simulation, capturing the key elements of the invasion process. We demonstrated that corner flows occur particularly in low-porosity media, where the smaller grain-grain distance hindered the corner-flow bridging. These insights could improve the CO2 geological storage and Enhanced Oil Recovery processes.