The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.

The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.

One way to reduce the amount of CO2 in the atmosphere for the mitigation of climate change is to capture the CO2 and inject it into geological formations. The most important public concern about carbon capture and storage (CCS) is whether stored CO2 will leak into groundwater sources and finally into the atmosphere. To prevent the leakage, the possible leakage paths and the mechanisms triggering the paths must be examined and identified. It is known that the leakage paths can be due to CO2 - rock interaction and CO2 &ndash / well interaction. The objective of this research is to identify the geochemical reactions of the dissolved CO2 in the synthetic formation water with the rock minerals of the Sayindere cap rock by laboratory experiments. It is also aimed to model and simulate the experiments using ToughReact software. Sayindere formation is the cap rock of the Caylarbasi, a southeastern petroleum field in Turkey. The mineralogical investigation and fluid chemistry analysis of the experiments show that calcite was dissolved from the cap rock core as a result of CO2- water- rock interaction. Using the reactive transport code TOUGHREACT, the modeling of the dynamic experiment is performed. Calcite, the main primary mineral in the Sayindere is dissolved first and then re-precipitated during the simulation process. The decreases of 0.01 % in the porosity and 0.03% in permeability of the packed core of the Sayindere cap rock are observed in the simulation. The simulation was continued for 25 years without CO2 injection. However, the results of this simulation show that the porosity and permeability are increased by 0.001 % and 0.004 %, respectively due to the CO2-water-rock mineral interaction. This shows that the Sayindere cap rock integrity must be monitored in the field if application is planned.

Large-scale geological storage of CO₂ is likely to bring CO₂ plumes into contact with existing wellbores and faults, which can act as pathways for leakage of stored CO₂ Modeling the flux of CO₂ along a leaky pathway requires transport properties along the pathway. We provide an approach based on the analogy between the leakage pathway in wells that exhibit sustained casing pressure (SCP) and the rate-limiting part of the leakage pathway in any wellbore that CO₂ might encounter. By using field observations of SCP to estimate transport properties of a CO₂ leakage pathway, we obtain a range of CO₂ fluxes for the cases of buoyancy-driven (post-injection) and pressure-driven (during injection) leakage. The fluxes in example wells range from background levels to three orders of magnitude higher than flux at the natural CO₂ seep in Crystal Geyser, Utah. We estimate a plausible range of fault properties from field data in the Mahogany Field using a shale gouge ratio correlation. The estimated worst-case CO₂ flux is slightly above background range. The flux along fault could be attenuated to zero by permeable layers that intersect the fault. The attenuation is temporary if layers are sealed at other end. Counterintuitively, greater elevation in pressure at the base of the fault can result in less CO₂ leakage at the top of the fault, because the capillary entry pressure is exceeded for more permeable layers. Since non-negligible leakage rates are possible along wellbores, it is important to be able to diagnose whether leakage is occurring. Concurrent pressure and temperature measurements are especially valuable because they independently constrain the effective permeability of a leakage path along wellbore. We describe a simple set of coupled analytical models that enable diagnosis of above-zone monitoring data. Application to data from a monitoring well during two years of steady CO₂ injection shows that the observed pressure elevation requires a model with an extremely large leakage rate, while the temperature model shows that this rate would be large enough to raise the temperature in the monitoring zone significantly, which is not observed. The observation well is unlikely to be leaking. Extraction of brine from the aquifer offers advantage over standard storage procedure by greatly mitigating pressure elevation during CO₂ injection. A proper management of the injection process helps reduce the risk of leakage associated with wellbores and faults. We provide strategies that optimize the injection of CO₂ which involve extraction of brine in two scenarios, namely injecting dissolved CO₂ and supercritical CO₂. For surface dissolution case we are concerned with bubble point contour, while for supercritical CO₂ injection we are concerned with breakthrough of CO₂ at extractors. In a surface dissolution project, the CO₂ concentration front shape when it reaches the saturation pressure contour defines the maximum areal extent of CO₂-saturated brine and hence the aquifer utilization efficiency. We illustrate the reduction of utilization efficiency due to heterogeneity of the aquifer. We develop an optimal control strategy of the injection/extraction rates to maximize the utilization efficiency. We further propose an optimal well pattern orientation strategy. Results show that the approach nearly compensates the reduction of utilization efficiency due to heterogeneity. In a supercritical CO₂ injection that involves brine extraction, the problem of avoiding breakthrough of CO₂ at extraction wells can be addressed by optimizing flow rates at each extractor and injector to delay breakthrough as long as possible. We use the Capacitance-Resistive Model (CRM) to conduct the optimization. CRM runs rapidly and requires no prior geologic model. Fitting the model to data recorded during early stages of CO₂ injection characterizes the connectivities between injection and brine-extraction wells. The fitted model parameters are used to optimize subsequent CO₂ injection in the formation. Field illustration shows a significant improvement in CO₂ storage efficiency. / text

L'effet de serre lié à l'émission de CO2 a conduit à des projets de stockage de ce gaz dans des formations réservoirs. Ces formations peuvent être traversées de failles et l'examen de la sûreté du stockage nécessite alors l'étude du risque de réactivation et de propagation de ces failles. Cette étude passe par des investigations approfondies portant sur des conditions de propagation des fractures sous sollicitations hydromécaniques. Cette thèse a pour objectif l'étude théorique et numérique de ces conditions ainsi que la simulation numérique de la propagation. La modélisation numérique des processus thermo-hydro-mécaniques dans les milieux poreux fracturés par la méthode des éléments finis (MEF) permet de simuler des phénomènes complexes et non linéaires. Les difficultés liées à l'intégration des équations d'échanges de fluide entre la fracture et la matrice environnante avec la MEF ont été résolues dans des travaux récents et nos simulations numériques ont pu être basées sur cette méthode. Dans un premier temps, nous avons modélisé l'écoulement transitoire dans et au voisinage d'une fracture soumise à une injection de fluide et nous avons étudié le facteur d'intensité des contraintes (FIC) à l'extrémité de la fracture dans le cadre de la théorie de la poroélasticité linéaire. Si les conditions d'injection sont maintenues constantes et la fracture n'évolue pas, l'écoulement tend vers un état stationnaire. Le FIC évolue au cours de la phase transitoire pour atteindre une valeur limite dans l'état stationnaire. La modélisation de l'écoulement transitoire est très coûteuse en temps de calcul et il est intéressant de trouver un moyen d'exploiter au mieux les résultats d'un calcul en état stationnaire. L'analyse théorique et les résultats des simulations numériques montrent en effet que le FIC calculé à l'état stationnaire peut fournir certaines bornes pour la propagation des fractures sous l'écoulement transitoire. Dans le cadre de la poroélasticité linéaire et de l'écoulement de Poiseuille dans les fractures, des expressions semi-analytiques pour le FIC à l'état d'écoulement stationnaire ont pu être dérivées. Pour des géométries simples, ces formules approximatives se révèlent efficaces pour discuter des conditions de propagation des fractures pour des cas typiques et simples de géométrie de la fracture et des conditions d'injection de fluide. Dans un deuxième temps, un Modèle de Fracture Cohésive (MFC) a été utilisé pour modéliser la propagation de fracture sur la base de l'endommagent. Ce modèle, basé sur un critère de rupture de Mohr–Coulomb modifié, permet de simuler l'endommagement de l'interface à la fois sous sollicitations en mode I et II. Une relation d'équivalence entre les paramètres de ce modèle et du modèle de Mécanique Linéaire de la Rupture (MLR) a été établie sur la base de la longueur de propagation de fracture sous des charges similaires. Cette relation permet l'extension de l'équivalence théorique entre MLR et MFC établie pour les matériaux fragiles et sur la base de critères énergétiques, à des matériaux quasi-fragiles et ductiles. On a d'ailleurs montré que le MFC permet de simuler certains phénomènes spécifiques tels qu'instabilités de propagation en mode I et II et le branchement de la fracture en mode II. Enfin, la prise en compte de la pression de fluide dans la fracture a permis d'obtenir un modèle de MFC couplé avec l'hydraulique qui a été implémenté dans un code numérique aux éléments finis en vue d'étudier la propagation des fractures sous sollicitations hydromécaniques. Des simulations numériques ont été réalisées afin d'étudier le risque de réactivation et de propagation des failles dans le contexte de stockage du CO2 en particulier dans une configuration de formation réservoir du type Bassin de Paris / Global warming effect related to CO2 emission has led to sequestration projects of this gas in reservoir formations. These formations can be crossed by faults and safety issue of storage requires the study of fault reactivation and propagation risk. This study goes through in-depth investigations of fracture propagation conditions under hydromechanical solicitations. This thesis aims at theoretical and numerical studies of these conditions and the numerical simulation of fracture propagation. Numerical modelling of thermo-hydro-mechanical processes in fractured porous media using Finite Element Method (FEM) allows the simulation of complex and nonlinear phenomena. Difficulties in integrating fluid mass exchange between fracture and surrounding matrix in the equations with FEM have been solved in recent works and our numerical simulations have been based on this progress. In a first step, we modelled transient flow subjected to a fluid injection and we studied the Stress Intensity Factor (SIF) at fracture tip in the framework of linear poroelasticity theory. If injection conditions are kept constant and the fracture does not evolve, the flow tends to a steady state. The SIF develops during transient phase to reach a limit value in the steady state. Modelling of transient flow is very time consuming and it is interesting to find a method to exploit the results of a calculation in steady state. Theoretical analysis and results of numerical simulations show that the SIF calculated at steady state can provide some bounds for fracture propagation under transient flow. In the framework of linear poroelasticity and Poiseuille flow in fractures, some semi-analytical expressions of SIF at steady state could be derived. For simple geometries, these approximate formulations are efficient to discuss fracture propagation conditions for typical and simple cases of fracture geometry and fluid injection conditions. In a second step, a Cohesive Zone/Fracture Model (CFM) was used to model fracture propagation on the basis of damage. This model, based on a modified Mohr-Coulomb failure criterion, simulates interface damage under both mode I and II loads. An equivalence relation between parameters of CFM and Linear Elastic Fracture Mechanics model (LEFM) was established on the basis of fracture propagation length under similar loads. This relationship allows the extension of theoretical equivalence between LEFM and CFM established for brittle materials and on the basis of energy criteria, for quasi-brittle and ductile materials. It has also shown that CFM can simulate specific phenomena such as propagation instabilities for mode I and II and fracture kinking under mode II. Finally, taking into account the fluid pressure in the fracture permitted to obtain a CFM coupled with hydraulic processes which has been implemented in a numerical finite element code to study fracture propagation under hydromechanical solicitations. Numerical simulations were performed to study the risk of fault reactivation and propagation in the context of CO2 injection in Paris Basin reservoir formation

Light transmission can be used to measure the amounts of certain constituents within a system by analyzing the amount of light they have absorbed. The aim of this study was to improve methods for light transmission measurements in two phase systems. In this study, the main reason is to be able to use light transmission for measurements of CO2-trapping in natural sandstone. The latter is something that does not exist today. The study investigated the possibility to use selected liquids that both represent an analogue CO2-brine system and have similar refractive index as each other to simplify Beer-Lamberts law. The simplification suggested that a change in light intensity within a system was controlled solely by the length of a liquid that had replaced another liquid. Two methods were implemented to test this. A tank containing high transparency sand and glycerol was injected several times with dyed oil in order to test equations developed to calculate the length of oil that light had passed. The glycerol and oil were chosen due the ratio between them in density and viscosity. These are properties that make them ideal for modelling the trapping of supercritical CO2 in sandstone saturated with brine. The other method for testing was to measure a coefficient of light absorption for the oil, then applying that coefficient to an injection of a known volume of oil. The analysis results showed that a linear relationship exists between difference in light intensity and the volume of oil in a system. The developed equation for oil length, as a function of light absorption specific for that oil, is sufficient for calculating the volume of oil in the system. It could not be used for calculating exact values in each part of the tank. The placement of oil was crucial to the measured light intensity for a single point. Oil occuring further back in the tank gave lower values of light intensity than oil occuring in the front. The study show that with further investigation into the role of oil placement in the light path, a simpler method could be developed for some light transmission measurements. The method could be used in its current form for modelling CO2 in sandstone but should be further developed if exact values are important / Light transmission är en teknik som används för att mäta mängden av en vätska eller gas genom att låta ljus passera genom det och se hur mycket ljuset minskade i styrka. Tekniken används idag bl.a. för att titta hur föroreningar sprider sig i sand. Vid dessa mätningar så har man en tank med glasväggar fylld av sand och vätska. Syftet med denna studie är att ta fram en metod som gör light transmission mer tillgängligt och enklare att använda. Målet är att ta fram en metod som är så pass allmän att den går att applicera på naturlig sand och sandsten. I sandstenen testas CO2-trapping i djup berggrund. Modelleringen av CO2-trapping i sandsten är något som inte existerar idag med hjälp av light transmission teknik. Metoden i denna studie bygger på att förenkla den formel som normalt används för att beräkna ljusförluster när en stråle ljus passerar genom ett material, Beer-Lamberts lag. Förenklingen sker genom att noggrant välja konstituenterna som används så att den refraktion av ljus som normalt sker mellan två medium försvinner. De konstituenter som skall anpassa är vätskor som ska representera flytande CO2 samt saltvatten. Genom att ta en bild som sedan jämförs med bilder under tiden en injektion av olja sker, så skall enligt teorin endast längden olja som ljuset passera förändra ljusets styrka. De vätskor som väljs är en hydraulolja och glycerol. Dessa väljs eftersom att de beter sig liknande hur CO2 beter sig i saltvatten under högt tryck. 2D experiment på skalor av tiotals cm gör det möjligt att studera hur heterogenitet i sandstenen påverkar hur mycket CO2 som kan fastläggas och därmed lagras på ett säkert sätt. Mer avancerade visualiseringstekniker klarar ofta bara små prover med längdskalor på någon cm. Dessa använder t.ex. röntgenstrålning. I studien används flera kyvetter fyllda med olja som placeras efter varandra för att mäta hur ljusmängden förändras beroende på längden olja den passerar. Detta samband testas sedan på en tank fylld med sand, glycerol och en känd mängd olja. Oljans ljusabsorption framtagen med kyvetter visade sig att inte gå att använda på den uppställning den testades på. Ett annat försök att ta fram ljusabsorptionskoefficienten för oljan gjordes genom att injicera en känd mängd olja i flera steg i samma uppställning som tidigare testats på. Inte heller detta försök gick att använda eftersom koefficienten varierade kraftigt beroende på injektionstillfälle samt mängden olja den beräknades för. Det visade sig finnas en stark korrelation mellan mängden olja i tanken och skillnad i ljusmängd. Det gick dock inte att skapa något generellt samband mellan mängden olja i en specifik punkt och skillnaden i ljus. Det visade sig ha stor betydelse i vilken del av tanken som oljan befann sig. Den olja som låg längre bak i tanken gav mindre ljusskillnad än den som låg längst fram mot glaset. På grund av det starka sambandet mellan ljusskillnad och oljemängd så tyder det på att metoden borde gå att bygga vidare på, men vidare studier krävs. Den metod som testas här måste utvecklas ytterligare för att gå att applicera på sand eller sandsten.

An extensive multi-channel seismic dataset acquired between 1970 and 1990 by Oljeprospektering AB (OPAB) has recently been made available by the Geological Survey of Sweden (SGU). This thesis summarizes four papers, which utilize this largely unpublished dataset to improve our understanding of the geology and CO2 storage capacity of the Baltic and Hanö Bay basins in southern Sweden. A range of new processing workflows were developed, which typically provide an improvement in the final stacked seismic image, when compared to the result obtained with the original processing. A method was developed to convert scanned images of seismic sections into SEGY files, which allows large amounts of the OPAB dataset to be imported and interpreted using modern software. A new method for joint imaging of multiples and primaries was developed, which is shown to provide an improvement in signal to noise for some of the seismic lines within the OPAB dataset. For the first time, five interpreted regional seismic profiles detailing the entire sedimentary sequence within these basins, are presented. Depth structure maps detailing the Outer Hanö Bay area and the deeper parts of the Baltic Basin were also generated. Although the overall structure and stratigraphy of the basins inferred from the reprocessed OPAB dataset are consistent with previous studies, some new observations have been made, which improve the understanding of the tectonic history of these basins and provide insight into how the depositional environments have changed throughout time. The effective CO2 storage potential within structural and stratigraphic traps is assessed for the Cambrian Viklau, När and Faludden sandstone reservoirs. A probabilistic methodology is utilized, which allows a robust assessment of the storage capacity as well as the associated uncertainty. The most favourable storage option in the Swedish sector of the Baltic Basin is assessed to be the Faludden stratigraphic trap, which is estimated to have a mid case (P50) storage capacity of 3390 Mt in the deeper part of the basin, where CO2 can be stored in a supercritical phase.

3D time-lapse seismics, also known as 4D seismics, have great potential for monitoring the migration of CO2 at underground storage sites. This thesis focuses on time-lapse analysis of 3D seismic reflection data acquired at the Ketzin CO2 geological storage site in order to improve understanding of the reservoir and how CO2 migrates within it. Four 3D seismic surveys have been acquired to date at the site, one baseline survey in 2005 prior to injection, two repeat surveys in 2009 and 2012 during the injection period, and one post-injection survey in 2015. To accurately simulate time-lapse seismic signatures in the subsurface, detailed 3D seismic property models for the baseline and repeat surveys were constructed by integrating borehole data and the 3D seismic data. Pseudo-boreholes between and beyond well control were built. A zero-offset convolution seismic modeling approach was used to generate synthetic time-lapse seismograms. This allowed simulations to be performed quickly and limited the introduction of artifacts in the seismic responses. Conventional seismic data have two limitations, uncertainty in detecting the CO2 plume in the reservoir and limited temporal resolution. In order to overcome these limitations, complex spectral decomposition was applied to the 3D time-lapse seismic data. Monochromatic wavelet phase and reflectivity amplitude components were decomposed from the 3D time-lapse seismic data. Wavelet phase anomalies associated with the CO2 plume were observed in the time-lapse data and verified by a series of seismic modeling studies. Tuning frequencies were determined from the balanced amplitude spectra in an attempt to discriminate between pressure effects and CO2 saturation. Quantitative assessment of the reservoir thickness and CO2 mass were performed. Time-lapse analysis on the post-injection survey was carried out and the results showed a consistent tendency with the previous repeat surveys in the CO2 migration, but with a decrease in the size of the amplitude anomaly. No systematic anomalies above the caprock were detected. Analysis of the signal to noise ratio and seismic simulations using the detailed 3D property models were performed to explain the observations. Estimation of the CO2 mass and uncertainties in it were investigated using two different approaches based on different velocity-saturation models.

Le stockage géologique du CO2 est l'une des diverses technologies étant explorées afin de réduire les émissions de carbone atmosphérique des processus industriels (i.e. combustion de l'énergie fossile). L'une des spécifiques caractéristiques de l'injection du CO2 en profondeur reste la possibilité de réactions géochimiques (dissolution-précipitation) entre la saumure réactive mobile (e.g. eau de formation enrichie en CO2) et la roche encaissante durant l'évolution spatiale et temporelle du CO2, conduisant à des modifications dans la structure des pores et par conséquent dans les propriétés d'écoulement du réservoir (e.g. la perméabilité k). Donc, ces changements structuraux peuvent largement contrôler l'injectivité, ainsi que le champ de pression dans le réservoir et aussi la propagation du CO2. Il demeure ainsi crucial d'explorer les changement dans les propriétés de réservoirs (e.g. structurales et hydrodynamiques) induits durant une injection de CO2 et explicitement les relations existantes entre eux (e.g. k ou surface réactive-Sr versus porosité- , k versus hétérogénéité de la roche), afin de développer des outils de modélisation prédictive des processus de transport et réactionnels se produisant durant une injection de CO2 et d'évaluer de façon fiable les risques. Dans le cas des réservoirs carbonatés, l'application des modèles prédictifs de transport réactif demeure toujours un enjeu, car contrainte par la forte hétérogénéité en leur sein ainsi que par l'incertitude dans la cinétique de réactions des minéraux carbonatés dans ce contexte. Dans cette optique, nous avons réalisé des expériences de percolation à travers des échantillons de roches carbonatées dans les conditions thermodynamiques de stockage en profondeur (T = 100°C et P =12 MPa). L'évolution de la perméabilité est suivie au cours des expériences ; et la variation de la porosité est calculée à partir des résultats d'analyses chimiques au ICP-AES des fluides de sortie échantillonnés. L'investigation des modifications apportées à la structure des pores est réalisée par le biais de la Micro-Tomographie haute résolution à rayon X, acquise au synchrotron de Grenoble (e.g. ESRF). Dépendant du régime de dissolution, contrôlé par la fabrique de la roche réservoir et la composition chimique de la saumuré chargée en CO2 (e.g. PCO2 engagée), on a observé qu'une modification de la structure de la roche peut soit améliorer soit détériorer (résultat atypique en contexte de dissolution) la valeur de la perméabilité k. Mots clés : Stockage géologique du CO2, transport, réactions géochimiques, structure des pores, propriétés hydrodynamiques, expériences de percolation de CO2, micro-tomographie à rayon X. / Geological storage of CO2 is one of diverse technologies being explored to reduce atmospheric carbon from industrial processes (i.e. fossil fuel combustion). One of the specific features of CO2 injection is the possibility of geochemical reactions (dissolution – precipitation) between mobile reactive brine (e.g. formation water enriched in CO2) and the host rock during the spatial and temporal evolution of CO2. That leads to modifications in the pore structure which in turn change the flow dynamics of the reservoir (e.g. the permeability k). Then, theses structural modifications can largely control the injectivity, so that the pressure field in the reservoir and also the CO2 propagation. Accordingly, it is crucial to explore the changes in the reservoir properties (e.g. structural and hydrodynamic) induced during a CO2 injection and specially the relationships between them (e.g. k or reactive surface-Sr versus porosity- , k versus rock heterogeneity), for developing predictive modelling tools of the transport and reaction processes occurring during a CO2 injection and reliable risk assessment. In the case of carbonate rocks, the application of the predictive models of transport and reaction is still challenging, because of their high heterogeneity so that the incertitude in the reaction kinetics of carbonate minerals. From this perspective, we realized brine-enriched in CO2 percolation experiments through carbonate rock samples in thermodynamic conditions expected during CO2 injection in deep reservoirs (T = 100°C et P =12 MPa). The permeability changes k(t) is monitored during the experiments and the porosity variation is calculated from chemical analyses of the sampled outlet fluids, using ICP-EAS. The pore structure modifications are investigated from high resolution X ray micro tomography images acquired from the synchrotron of Grenoble (ESRF). Depending to the dissolution regime, controlled by the reservoir rock fabric and the chemical composition of the brine (e.g. PCO2), we observed that a modification of pore structure can either improve (atypical result in dissolution context) or impair the value of the permeability k. Keywords: CO2 geological storage, transport, geochemical reactions, pore structure, hydrodynamic properties, brine enriched in CO2 percolation experiments, X ray microtomography.

Le stockage géologique du CO2 dans les aquifères salins représente une stratégie prometteuse pour la réduction des émissions de CO2 anthropiques. Ce type de stockage requiert des connaissances fondamentales afin d'évaluer les scénarios d'injection, d'estimer la capacité des réservoirs et les risques de fuite. C'est dans ce contexte que des outils microfluidiques haute pression/haute température ont été développés afin d'étudier différents mécanismes liés aux technologies de stockage de CO2. Les laboratoires géologiques sur puce (GLoCs) permettent de mener des expériences à des conditions de pression et de température typiques des réservoirs (25 < T < 50°C, 50 < p < 10 MPa) et d'en mimer des propriétés géologiques.Ce manuscrit présente dans un premier temps les stratégies de fabrication des GLoCs et l'accès à leurs caractéristiques (porosité et perméabilité). La détection du CO2 directement au sein de GLoCs grâce à l'implémentation de fibres optiques par spectroscopie infrarouge est ensuite présentée, ainsi que la mise en œuvre de la technique de laminographie X menées à l'ESRF pour le suivi de dissolution de carbonates dans des microcanaux. Le manuscrit explicite ensuite les investigations, menées avec des GLoCs concernant les différents mécanismes de piégeage du CO2 à l'échelle du pore. La visualisation directe et le traitement d'image ont permis de suivre l'évolution des phases de CO2 et des phases aqueuses au sein du GLoC et les mécanismes de déplacement et de saturation. Enfin, les travaux en cours sont exposés, comme les expériences de drainage avec des saumures réactives ou la formation d'hydrates au sein de milieux poreux. / CO2 geological storage in deep saline aquifers represents a mediation solution for reducing the anthropogenic CO2 emissions. Consequently, this kind of storage requires adequate scientific knowledge to evaluate injection scenarios, estimate reservoir capacity and assess leakage risks. In this context, we have developed and used high pressure/high temperature microfluidic tools to investigate the different mechanisms associated with CO2 geological storage in deep saline aquifers. The silicon-Pyrex 2D porous networks (Geological Labs On Chips) can replicate the reservoir p,T conditions (25 < T < 50°C, 50 < p < 10 MPa), geological and topological properties. This thesis manuscript first highlights the strategies developed during this work to fabricate the GLoCs and to access to global characteristics of our porous media such as porosity and permeability, which are later compared to numerical modelling results. The carbon dioxide detection in GLoCs mimicking p,T conditions of geological reservoirs by using the direct integration of optical fiber for IR spectroscopy is presented. I then detail the strategies for following the dissolution of carbonates in GLoCs with X-rays laminography experiments.Then, the manuscript focuses on the use of GLoCs to investigate each CO2 trapping mechanism at the pore scale. The direct optical visualization and image processing allow us to follow the evolution of the injected CO2/aqueous phase within the reservoir, including displacement mechanisms and pore saturation levels.Eventually, I present the ongoing works such as experiments with reactive brines and hydrates formations in porous media.