Carbon dioxide enhanced oil recovery (CO2EOR) is a proven and available technology used to produce incremental oil from depleted fields. Although this technology has been used successfully onshore in North America and Europe, projects have maximised oil recovery and not CO2 storage. While the majority of onshore CO2EOR projects to date have used CO2 from natural sources, CO2EOR is now more and more being considered as a storage option for captured anthropogenic CO2. In the North Sea the lack of low cost CO2, in large volumes, has meant that no EOR projects have utilised CO2 as an injection fluid. However CO2EOR has the highest potential of all EOR techniques to maximise recovery from depleted UK oil fields. With the prospect of Carbon Capture and Storage (CCS) capturing large tonnages of CO2 from point source emission sites, the feasibility of CO2EOR deployment in the North Sea is high. This thesis primarily aims to address a number of discrete issues which assess the effectiveness of CO2EOR to both produce oil and store CO2. Given the fundamental shift in approach proposed in North Sea CO2EOR projects, the carbon balance of such projects is examined. Using a life cycle accounting approach on a theoretical North Sea field, we examine whether offshore CO2EOR can store more CO2 than onshore projects traditionally have, and whether CO2 storage can offset additional emissions produced through offshore operations and incremental oil production. Using two design scenarios which optimise oil production and CO2 storage, we find that that net GHG emissions were negative in both ‘oil optimised’ and ‘CO2 storage optimised’. However when emissions from transporting, refining and combusting the produced crude oil are incorporated into the life cycle calculations the ‘oil optimised scenario’ became a net emitter of GHG and highlights the importance of continuing CO2 import and injection after oil production has been maximised at a field. This is something that has not traditionally occurred. After assessing rates of flaring and venting of produced associated gas at UK oil fields it is found that the flaring or venting of reproduced CH4 and CO2 has a large control on emissions. Much like currently operating UK oil fields the rates of flaring and venting has a control on the carbon intensity of oil produced. Here values for the carbon intensity of oil produced through CO2EOR are presented. Carbon intensity values are found to be similar to levels of current UK oil production and significantly lower than other unconventional sources. As well as assessing the climate benefits of CO2EOR, a new assessment of CO2EOR potential in Residual Oil Zones (ROZ) is also made. ROZ resource, which is thought to add significant potential to both the oil reserves and CO2 storage potential in some US basins, is here identified in the North Sea for the first time. Based on the foundation of North Sea hydrodynamics study, this thesis identifies the Pierce field as a candidate ROZ field where hydrodynamic tilting of the oil water contact has naturally occurred leaving a zone of residual oil. To test the feasibility of CO2EOR in such a zone a methodology is presented and applied. Notably the study highlights that in this case study recoverable reserves from the ROZ may approach 20% of total field recoverable reserves and have the capability to store up to 11Mt of CO2. While highlighting the CO2EOR potential in the ROZ the thesis discusses the importance in expanding the analysis to quantify its importance on a basin scale. Discussion is also made on whether new resource identification is necessary in a mature basin like the North Sea. With CO2EOR being considered as a feasible option for storing captured anthropogenic CO2, it is important to assess the security of storage in CO2EOR. Using real geochemical and production data from a pilot CO2EOR development in Western Canada two approaches are used to assess the partitioning of CO2 between reservoir fluids through time. Using a number of correlations it is found that CO2 dissolution in oil is up to 7 times greater than in reservoir brine when saturations between the two fluids are equal. It is found that after two years of CO2 injection solubility trapping accounts for 26% of injected CO2. The finding that significantly more dissolution occurs in oil rather than brine indicates that CO2 storage in EOR is safer than in brine storage. However a number of factors such as the increase in oil/CO2 mobility due to CO2 injection is also discussed. The overall conclusion from the work is that CO2EOR in the North Sea has the potential to be an effective way of producing oil and storing CO2 in the North Sea. A number of design, operational and accounting factors are however essential to operate an exemplar CO2EOR project where low carbon intensity oil can be produced from a mature basin while storing large tonnages of captured anthropogenic CO2.

Mon sujet de thèse concerne les propriétés acoustiques et sismiques des formations non consolidées. Ce sujet est très mal connu, depuis la surface d'une part parce que la physique des milieux non consolidés est encore mal connue, et en forage d'autre part parce que ces milieux ne sont pas stables mécaniquement. Toute mesure en forage demande donc la pose d'un tubage et la réalisation des mesures à travers ce tubage. Dans le cadre de ma thèse, on appliquera premièrement ces mesures aux domaines du stockage de CO2 dans les formations géologiques, et ensuite à celui des glissements de terrains. Dans ce cadre, des mesures ont été réalisées sur les sites de Maguelone et de Svelvik pour le stockage géologique du CO2, et de Lodève pour les glissements de terrain.Le site expérimental Maguelone (France) a fait l'objet de la surveillance géophysique de la surface et en forages pendant les expériences d'injection de gaz dans un réservoir souterrain de roches clastiques peu profonde. En particulier, les profils sismiques verticaux (PSV) et les logs Sonique (derrière un tubage PVC) ont été enregistrés dans deux puits situés à quelques mètres du puits d'injection, avant, pendant et après une série d'injections de gaz. Les premieres arrivées pour les PSV ont été obtenues par le pointage (picking), et interprétées en termes de modèles de vitesses sismiques. Les données Sonique, après les avoir comparées avec les autres mesures pétrophysiques et géophysiques, ont été traitées et analysées en termes de vitesses et amplitudes. Avant l'injection, la comparaison des vitesses sismiques et d'amplitude entre les expériences dans un seul puits (MAG1), met en évidence l'impact de l'injection de gaz sur les propriétés élastiques des sédiments détritiques poreux au niveau du site d'injection, ce qui indique une augmentation de la saturation en gaz en face des couches sableuses et de couches de gravier. En tout, time-lapse VSP et les sonic logs, fournissent un moyen pour détecter et surveiller l'injection et le stockage de gaz dans des réservoirs géologiques, conduisant à une vue sur la dynamique du sous-sol au cours du temps. L'objectif du projet de CO2FieldLab (Svelvik Site_ Norvège) était de démontrer que les méthodes de surveillances adéquates peuvent être déployées pour documenter les risques de fuites de CO2 dans des réservoirs souterrains. Pour ce faire, une expérience d'injection peu profonde dans le sédiment perméable a été conçu et réalisé à Svelvik (Norvège) en Septembre 2011. L'objectif était de produire une fuite de CO2 afin d'évaluer la sensibilité relative de plusieurs outils de surveillance des émissions de CO2 géochimiques et géophysiques. Cette étude a mis en évidence le potentiel des méthodes acoustiques pour la surveillance et la détection de faible profondeur le stockage du CO2 et de la migration. Dans chacun des sites de l'étude, les séries de techniques ont été utilisées avec succès pour monitorage le stockage du CO2 et de la migration dans les réservoirs peu profonds, ces techniques se combinent les approches géophysiques et géochimiques. Sur le site de Lodève, mon travail s'est focalisé sur l'analyse de diagraphies et d'images ultrasoniques de parois obtenues sur seulement 20 mètres en trou nu dans la zone de déformation d'un glissement de terrain actif dans cette région. Des profils sismiques de surface ont également été enregistrés. Par contre, du fait de l'instabilité mécanique du forage, une légère déformation élastique ovale du forage a été mise en évidence aussi bien sur les images en distance qu'en amplitude. En utilisant la méthodologie utilisée traditionnellement pour l'analyse de déformations cassantes en forage (appelées "breakouts"), on note que la direction d'ovalisation correspond à la direction de plus grande pente du flanc de colline affectée par le glissement traversé par le forage entre 60 et 70 mètres, dans l'intervalle où les images ont été enregistrées. / The objective of My thesis concerns the acoustic and seismic properties of unconsolidated formations. This topic is poorly known, from the surface -of one hand- because the physical of unconsolidated environments is still poorly understood, and in the well on the other hand where these environments are not mechanically stable. Therefore any downhole measure requests the installation of a casing and taking measurements through this casing. In my thesis, these measurements were used for the geological storage of CO2, and then in the landslide. In this context, measures have been carried out on sites Maguelone and Svelvik for the geological storage of CO2, and in the Lodeve site for landslides.The Maguelone experimental site (France) has been the subject of surface and downhole geophysical monitoring of gas injection experiments in a shallow subsurface clastic reservoir. In particular, vertical seismic profiles (VSP) and downhole SONIC logs (through PVC liners) were recorded in two holes located within meters of the gas injection hole, before, during and after a series of gas injections. VSP first-arrival times were obtained by picking, and interpreted in terms of seismic velocity models. The sonic data, once compared to other logs and core petrophysical measurements, have been processed and analyzed in terms of velocities and amplitudes. Before injection. The comparison of seismic velocities and amplitude between experiments for a single hole brings out the impact of gas injection on the elastic properties of the porous clastic sediments at the injection site, suggesting an increase in gas saturation in front of the sandy and gravel-rich layers. . In all, time-lapse VSP and sonic logging through PVC provide a means to detect and monitor gas injection and storage in geological reservoirs, leading to a view on subsurface dynamics over time. The objective of the CO2FieldLab project (Svelvik site_ Norway) was to demonstrate that adequate monitoring methods can be deployed to document potential leaks of CO2 from subsurface reservoirs. For this, a shallow injection experiment through permeable sediment was designed and conducted at Svelvik (Norway) in September 2011. The goal was to produce a CO2 leak in order to assess the relative sensitivity of several geochemical and geophysical CO2 monitoring tools. This study highlighted the potential of acoustic methods for shallow monitoring and detecting of the CO2 storage and migration. In each of the study sites, the series of techniques have been successfully used to monitor CO2 storage and migration in the shallow reservoirs, these techniques combine geophysical and geochemical approaches On the Lodeve site, my work focused on the well logging analyzes especially the ultrasonic images obtained 20 meter only of the hole in the deformation zone un active landslide in the region. A slight elastic deformation oval of the hole was demonstrated both the distance and amplitude images. Using the methodology traditionally used for the analysis of the breakouts, we have noted that the ovalisation direction corresponds to the direction of slope of the hillside affected by slipping, traversed by the well between 60 and 70 meters of depth, the interval were the image ultrasonic recorded.

[pt] Os mecanismos envolvidos na produção de metano e no sequestro de CO2 no carvão são complexos, tendo em vista grande quantidades de fatores envolvidos no processo. O entendimento do comportamento mecânico do carvão assim como a caracterização de sistema poroso é de fundamental importância para o êxito de um projeto de explotação. Esse trabalho visou à caracterização de amostras de carvão oriundas da camada Barro Branco. A fim de caracterizar o sistema poroso do material, uma campanha de análises foi programada como: microtomógrafo, microscopia eletrônica de varredura (MEV), micropermiametria e porosimetria por injeção a mercúrio. Ensaios mecânicos foram realizados visando à caracterização mecânica do material e a validação de um modelo constitutivo. O carvão apresentou comportamentos mecânicos de resistência e deformabilidade consistentes e com pouca variabilidade, o que permitiu um ajuste confiável da envoltória de resistência de Mohr-Coulomb bem como o do modelo constitutivo elastoplástico de Lade-Kim. / [en] Mechanisms involved in geological storage of CO2 and eventual production of methane are complex due to a number of different factors involved. One of the important factors to be taken into account is the geomechanical behaviour of coal, key to the success of the exploration as well as the characterization of the pore structure of the material.Coal can be regarded as a sedimentary rock possessing two perpendicular families of microfissures called cleats.This work presents results of an experimental program aiming at the characterization of the mechanical properties of coal from the Barro Branco formation. A constitutive model (Lade-Kim s model) was tested in order to check its validity in the representation of the stress-strain-strength behaviour of the coal. Lade-Kim s model is well accepted for the representation of the mechanical behaviour of soft rocks. Furthermore, in order to characterize the porous structure of the material, a number of tests were performed such as: X Ray Micro CT scan, scanning electron microscopy, minipermeameter determination of permeability and mercury injection porosimetry.

[pt] Atrelado aos cenários cada vez mais complexos de extração de energia, o estudo de fenômenos acoplados em meios porosos - notadamente térmicos, hidráulicos, químicos e mecânicos - tem se apresentado como essencial na previsão de comportamento de meios geológicos no que diz respeito à disposição de rejeitos radioativos, armazenamento de dióxido de carbono, engenharia de reservatórios geotérmicos e geomecânica de reservatórios. Assim, este trabalho objetiva desenvolver um esquema de acoplamento termo-hidro-mecânico-químico iterativo visando a simulação do armazenamento geológico de dióxido de carbono, empregando um simulador de fluxo composicional (GEM) e um programa de análise de tensões (ABAQUS ou CHRONOS). A idealização das metodologias de acoplamento foi efetuada através dos processos hidro-mecânico, termo-hidro-mecânico e termo-hidro-mecânico-químico, bem como as validações e aplicações em casos reais. Os casos de validação, realizados empregando modelos simplificados monofásicos, apresentaram resultados satisfatórios quanto ao comportamento hidro-mecânico e termo-hidro-mecânico. Adicionalmente às validações, os esquemas termo-hidro-mecânico e termo-hidro-mecânico-químico foram aplicados em dois casos reais de armazenamento de CO2 apresentados na literatura, projeto In Salah (Argélia) e aquífero Utsira (Noruega), respectivamente. De maneira geral, os resultados encontrados, para ambos os casos estudados, representaram acuradamente as respostas encontradas em campo, fato que evidencia a qualidade, robustez e aplicabilidade dos esquemas de acoplamento propostos neste trabalho. / [en] Considering the increasingly complex scenarios of energy extraction, the study of coupled phenomena in porous media - notably thermal, hydraulic, chemical and mechanical - has been considered as essential in order to predict the behavior of geological media with regard to radioactive waste storage, CO2 geological storage, geomechanics of geothermal reservoirs and reservoir geomechanics. Thus, this work aims to develop a thermo-hydro-mechanical-chemical iterative coupling scheme in order to simulate the geological storage of CO2, employing a compositional flow simulator (GEM) and a stress analysis program (ABAQUS or CHRONOS). The idealization of the coupling methodologies was carried out through the processes hydro-mechanical, thermo-hydro-mechanical and thermo-hydro-mechanical-chemical, as well as the validations and applications in real cases. The validation cases, performed employing simplified single-phase models, presented satisfactory results regarding the hydro-mechanical and thermo-hydro-mechanical behaviors. Additionally to the validations, the thermo-hydro-mechanical and thermo-hydro-mechanical-chemical schemes were applied in two real cases of CO2 geological storage reported by the literature, In Salah project (Algeria) and Utsira aquifer (Norway), respectively. In general, the results found, in both cases studied, accurately represented the behavior observed in the field, which in turn highlights the accuracy, robustness and applicability of the coupling schemes proposed in this work.

Cette thèse concerne l'étude des risques associés aux projets de CTSC (Captage, Transport et Stockage de CO2) dont le développement est prévu à l'échelle industrielle. Les projets de CTSC sont des systèmes sociotechniques complexes pour lesquels une approche systémique de management des risques est nécessaire. L'approche doit couvrir les différents aspects du risque pour analyser l'influence de la dynamique des risques sur la dynamique des projets. Une méthodologie systémique de management des risques est proposée. Cette méthodologie est fondée sur les concepts de la pensée systémique, de l'approche STAMP (Systems-Theoretic Accident Model and Processes) développée au sein du Massachusetts Institute of Technology, et de la dynamique des systèmes. L'objectif est de modéliser et d'analyser la structure de contrôle de sécurité impliquée dans un projet de CTSC. La structure de contrôle de sécurité est la structure organisationnelle des parties prenantes (contrôleurs) qui sont responsables de maintenir les contraintes de la sécurité. L'objectif de cette structure de contrôle de sécurité dans cette thèse est d'éviter le retard ou l'échec des projets de CTSC. Cet objectif a été reformulé comme étant la définition et le management des risques majeurs qui pourraient empêcher ou limiter le maintien des contraintes de sécurité. Les risques ont été d'abord identifiés et classés selon huit catégories : Technique, SSE (Santé, Sécurité et Environnement), Politique/Stratégie, Réglementation, Organisationnel/Humain, Financier/Economique, Social et Projet. Les risques majeurs liés aux phases amont ont été extraits et modélisés en utilisant la méthodologie proposée. Les rétroactions affectant la propagation et l'amplification de chaque risque ont été étudiées. Les structures de contrôle de sécurité, le contexte et les risques associés des projets de Barendrecht, de Lacq et de Weyburn ont été analysés. L'application de la méthodologie sur ces trois retours d'expériences permet de proposer un modèle générique de contrôle de sécurité pour les projets de CTSC. L'accent est mis sur le rôle majeur des facteurs endogènes conduisant à l'échec des projets de CTSC. Ce modèle met en évidence les flux d'information et de communication entre les parties prenantes qui conduisent à améliorer leurs modèles mentaux et leurs décisions. / This thesis is concerned with understanding the risks associated with the development of CTSC (Capture, Transport & Storage of CO2) projects up to industrial scales. CTSC projects are complex sociotechnical systems for which a systemic risk management approach is required. The approach has to cover different aspects of risk in order to analyze how dynamics of risks affect dynamics of projects. A systemic risk management framework is proposed based on the concepts of systems thinking, STAMP (Systems-Theoretic Accident Model and Processes), developed at the Massachusetts Institute of Technology, and system dynamics. The objective is to model and analyze the safety control structure involved in a CTSC project. Safety control structure is the organizational structure of stakeholders (controllers) who are responsible for maintaining safety constraints. The goal of safety control structure in this work is to prevent CTSC project delay or failure. This goal has been rephrased as definition and treatment of major risks that could avoid maintaining safety constraints. The risks have been firstly identified and classified in eight main categories including Technical, HSE (Health, Safety and Environment), Policy/Strategy, Legal, Organizational/Human, Financial/Economic, Social and Project. The major risks related to the phases prior to engineering have been extracted and modeled by the proposed methodology. Feedback networks affecting the amplification of each risk have been studied. Safety control structures, context and associated risks of Barendrecht, Lacq and Weyburn projects have been analyzed in order to propose a generic safety control model for CTSC projects. Emphasis is placed on the significance of finding endogenous explanations for the failure of CTSC projects. The model highlights the flow of information and communication among stakeholders leading to improve their mental models and decisions.

Dans le cadre du stockage géologique de gaz acides, il est impératif de garantir l'intégrité des matériaux sollicités afin d'assurer un confinement pérenne du fluide injecté. Le but de ce travail de thèse est d'étudier, par le biais de modélisations expérimentales, les phénomènes pouvant être responsables de la déstabilisation du système et qui peuvent conduire à des fuites du gaz stocké. Le premier modèle expérimental, appelé COTAGES a permis d'étudier les effets de la déstabilisation thermique provoquée par l'injection d'un gaz à température ambiante dans un réservoir chaud. Ce dispositif a permis de mettre en évidence un transfert de matière important depuis la zone froide (30°C) vers la zone chaude (100°C) conduisant à des modifications des propriétés pétrophysiques. Ces résultats soulignent l'importance de la température d'injection sur la conservation des propriétés d'injectivité du système. Le second modèle, appelé "Sandwich" a permis d'étudier le comportement de l?interface entre la roche couverture (argilite COX) et le ciment de puits. Les expériences batch du modèle Sandwich en présence de CO2 ont permis de mettre en évidence une fracturation de l'interface provoquée par la carbonatation précoce du ciment. Ces résultats soulignent l'importance de l'état initial de la roche couverture dans la séquestration du fluide injecté. Le troisième modèle expérimental est le modèle MIRAGES. Ce dispositif innovant permet d'injecter en continu un flux de CO2 dans un échantillon. Les résultats ont mis en évidence un colmatage partiel de la porosité inter-oolithe à proximité du puits d'injection, ainsi qu'une carbonatation du ciment sous la forme d'un assemblage calcite/aragonite / In the framework of the CO2 storage, it is crucial to ensure the integrity of the solicited materials in order to guarantee the permanent confinement of the sequestrated fluids. Using experimental simulation the purpose of this work is to study the mechanisms which could be responsible for the system destabilization and could lead CO2 leakage from the injection well. The first experimental model, called COTAGES allows studying the effects of the thermal destabilisation caused by the injection of a fluid at 25°C in a hotter reservoir (submitted to the geothermal gradient). This device allows demonstrating an important matter transfer from the cold area (30°C) toward the hot area (100°C). These results highlight the importance of the injection temperature on the injectivity properties and on the possible petrophysical evolutions of the near well. The second model, called ?Sandwich?, allow studying the behaviour of the interface between caprock (COX argillite) and well cement. Indeed, interfaces between the different rock and the well materials represent a weakness area (differential reactivity, fracturing?). Batch experiments carried out with this device in presence of CO2 show the fracturing of the interface caused by the early carbonation of the cement. The third experimental model, called MIRAGES is an innovative device which allows injecting continuously CO2 in a core sample. Samples made of Lavoux limestone and well cement reproduce the injection well at 1/20 scale. Results show a partial filling of the inter-oolithic porosity close to the injection well, and also the carbonation of the cement according to an assemblage of calcite/aragonite

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-05-03T11:34:42Z No. of bitstreams: 1 disserta??o Roger vers?o biblioteca.pdf: 9741593 bytes, checksum: 510807346e33704b6f1650648b1f1b19 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-05-14T11:17:02Z (GMT) No. of bitstreams: 1 disserta??o Roger vers?o biblioteca.pdf: 9741593 bytes, checksum: 510807346e33704b6f1650648b1f1b19 (MD5) / Made available in DSpace on 2018-05-14T11:48:12Z (GMT). No. of bitstreams: 1 disserta??o Roger vers?o biblioteca.pdf: 9741593 bytes, checksum: 510807346e33704b6f1650648b1f1b19 (MD5) Previous issue date: 2018-01-15 / Developing technologies for the capture and geological storage of CO2 has been a constant challenge of the scientific community in the search for solutions that can reduce the environmental impacts caused by the release of this gas into the atmosphere. However, its storage in depleted oil wells has been shown to be a very important point, since the materials applied in wells can suffer degradation in the presence of CO2 in the supercritical state and at high pressures. The objective of this work is to evaluate the performance of the class G cement paste used in cementation of wellbore under conditions of geological carbon storage with replacement of part of the cement by pozoanic materials such as fly ash from the fossil fuel burning of the Candiota Thermoelectric Plant, and synthetic zeolites (4A-1 e 4A-2). The contents of the pozalanas used in substitution of the cement were 5% and 10% in weight. The medium in which samples were submitted for degradation tests was CO2 saturated water at 15 MPa pressure and 90 ?C for 7 and 14 days. Scanning Electron Microscopy (SEM), XRay Diffraction (XRD) and compressive strength tests were the characterization techniques used in this work. The results showed that the use of fly ash increased the compressive strength of the samples after 14 days, mainly for higher percentage of cement replacement by this material (10%), but its chemical degraded layer increased. In case of zeolites 4A-1 use, a lower compressive strength was observed compared to the standard paste, but the degraded layer was reduced. When zeolites 4A-2 were used significant loss of compressive strength was observed from 7 to 14 days, mainly for the proportion of the mixture of 10% and its degraded layer also reduced. / Desenvolver tecnologias para a captura e armazenamento geol?gico de CO2 tem sido um desafio constante da comunidade cient?fica na busca de solu??es que possam reduzir os impactos ambientais provocados pela libera??o desde g?s na atmosfera. Por?m, seu armazenamento em po?os depletados de petr?leo tem se mostrado o ponto mais desafiador, pois os materiais aplicados nestes po?os podem sofrer degrada??o na presen?a de CO2 em estado supercr?tico e em altas press?es. Este trabalho tem como objetivo avaliar o desempenho da pasta de cimento classe G, utilizada na cimenta??o e tamponamento dos po?os, em condi??es de armazenamento geol?gico de carbono com substitui??o de parte do cimento por materiais pozol?nicos. O material utilizado foi as cinzas volantes, oriundas da queima de carv?o mineral da Usina Termoel?trica de Candiota, e ze?litas 4A comerciais sint?ticas (4A-1 e 4A-2). Os teores utilizados das pozalanas em substitui??o ao cimento foram 5% e 10% em massa. O meio em que foram submetidas as amostras foi de ?gua saturada com CO2 a 15 MPa de press?o a 90? C por 7 e 14 dias. A Microscopia Eletr?nica de Varredura (MEV), a Difra??o de Raios X (DRX) e o teste de resist?ncia ? compress?o foram as t?cnicas de caracteriza??o utilizadas neste trabalho. Os resultados obtidos mostram que o uso de cinzas volantes aumentou aos 14 dias a resist?ncia ? compress?o das amostras, principalmente para maior a porcentagem de substitui??o do cimento por este material (10%), por?m a camada alterada quimicamente aumentou. Quando utilizadas as ze?litas 4A-1, notou-se uma menor resist?ncia ? compress?o que a pasta padr?o, mas a camada degradada reduziu. No caso das ze?litas 4A-2, foi constatada a perda significativa de resist?ncia ? compress?o dos 7 para 14 dias, principalmente para a amostra contendo 10% dessa zeolita, sendo que a camada alterada quimicamente tamb?m reduziu.

Depuis le milieu des années 90, la minéralisation in situ du CO2 est envisagée comme une solution durable et efficace pour limiter ses émissions anthropiques vers l'atmosphère. Il s'agit de récupérer le CO2 émis par certaines industries pour le piéger en profondeur sous forme minérale (carbonates) dans les aquifères mafiques et ultramafiques naturels (de type basaltes et péridotites). La carbonatation du CO2 a été largement décrite dans les systèmes naturels où elle apparait à travers une série de réactions chimiques couplées au transport des espèces réactives dans le fluide. Plusieurs expériences en réacteurs fermés ont été menées depuis une quinzaine d'années afin de mieux comprendre les paramètres physico-chimiques contrôlant ces réactions. Mais très peu d'études n'ont encore caractérisé les processus de transport-réactif au cours de l'injection et de la minéralisation in situ du CO2 dans ces roches.Ces travaux visent à répondre à 3 principaux objectifs : (i) caractériser l'évolution des chemins réactifs lors de l'injection de CO2 dans des roches (ultra-)mafiques, (ii) mesurer les effets en retour des réactions sur les propriétés hydrodynamiques du milieu et (iii) quantifier le rendement et la pérennité des processus sur le long terme. Ils s'appuient sur le développement de protocoles expérimentaux pour (i) reproduire l'injection de CO2 dans les roches (ultra-)mafiques et (ii) caractériser les réactions à l'aide d'une série d'outils géochimiques et analytiques de l'échelle atomique à centimétrique. Trois séries d'expériences de percolation réactive ont été réalisé sur des agrégats (ultra-)mafiques relativement simples (olivines de San Carlos et d'Hawaii) et plus complexes (basaltes de Stapafell) dans des conditions de P-T-confinement in situ (Ptot=10-25 MPa ; T=180-185°C;Pconf=15-28 MPa).Les résultats obtenus ont permis de différencier plusieurs chemins réactifs dans ces systèmes en fonction du transport du fluide, de la porosité du milieu, des hétérogénéités locales de la roche, de la minéralogie et/ou des variations locales de la composition chimique du fluide. Les calculs du bilan de masse ont révélé une minéralisation efficace du CO2 contrôlée par les propriétés chimiques et hydrodynamiques du milieu. Mais certaines réactions associées à l'altération des roches (ultra-)mafiques (hydratation) ont des effets en retour négatifs sur les propriétés réservoirs de la roche (porosité, perméabilité) pouvant compromettre la pérennité du stockage du CO2 dans les aquifères naturels sur le long terme.Ces nouvelles données permettront aux modèles numériques de mieux simuler la carbonatation des roches (ultra-)mafiques en connaissant les propriétés hydrodynamiques du milieu et les hétérogénéités structurales du réservoir. Elles suggèrent aussi qu'un meilleur contrôle de certains paramètres d'injection, comme le débit ou la composition du fluide injecté (ex: pCO2), permettrait d'améliorer le taux et le rendement de la carbonatation. / Since the mid-90s, in situ mineralization of CO2 has been considered as a safe and efficient solution to mitigate its anthropogenic emissions to the atmosphere. It is to recover the CO2 emitted by some industries and trap it in the mineral form (carbonates) in mafic and ultramafic aquifers (e.g. basalts and peridotites). The carbonation of CO2 has been widely described in natural systems where it occurs through a series of complex chemical reactions coupled to the transport of reactive species in the fluid. Numerous experiments have been conducted in batch reactors over the past fifteen years to better understand the physico-chemical parameters controlling the carbonation of (ultra-)mafic rocks. But few studies have further characterized the coupling reactive-transport processes during the injection and in situ mineralization of CO2 in these rocks.This work aims to meet 3 main objectives: (i) characterize changes in reaction paths during the injection of CO2 in (ultra-)mafic systems, (ii) measure the feedbacks effects of chemical reactions on the hydrodynamic rock properties and (iii) quantify the efficiency and sustainability of such processes over long time periods. It is based on the development of experimental protocols to (i) reproduce the injection of CO2 into (ultra-)mafic rocks and (ii) characterize the reactions using a series of geochemical and analytical tools from the atomic to the centimetric scale. Three series of reactive percolation experiments have been performed on (ultra-)mafic aggregates from relatively simple (olivines from San Carlos and Hawaii) to more complex samples (basalts from Stapafell) under in situ P-T-containment conditions (Ptot=10-25 MPa; T=180-185°C; Pcont=15-28 MPa).The results allowed us to differentiate several reactions paths in these systems depending on the fluid transport, rock porosity, local hydrodynamic properties, mineralogy and/or local changes in the fluid composition. Mass balance calculations have revealed an efficient mineralization of CO2 in the samples. It is controlled by the chemical and the hydrodynamic properties of the rock at the pore scale. But some reactions associated with the alteration of (ultra-)mafic rocks (e.g. hydration) have negative feedbacks effects on the reservoir rock properties (porosity and permeability) that may compromise the sustainability of CO2 storage in natural aquifers in the long term.These new supporting data will allow numerical models to better simulate the carbonation of (ultra-)mafic rocks knowing the hydrodynamic properties and the structural heterogeneities of the reservoir. They also suggest that a better control of some injection parameters, such as the flow injection rate and the injected fluid composition (e.g. pCO2), would improve the rate and yield of CO2 mineralization in these systems.

Ces travaux de thèse s'intéressent à l'étude du comportement d'une discontinuité dans un géomatériau sous sollicitations chemo-mécaniques à l'échelle du laboratoire. Des essais de traction-compression cyclique étudient la refermeture d'une fissure. Ils indiquent que les déformations inélastiques seraient gouvernées en partie par les frottements générés lors du ré-emboîtement des lèvres de la discontinuité, non correspondantes du fait des contraintes internes. Des joints rocheux altérés chimiquement sous sollicitation tangentielle sont étudiés au travers d'essais de cisaillement direct : le comportement des joints dégradés est profondément modifié du fait de la diminution des propriétés mécaniques du matériau de part et d'autre de la discontinuité et de l'accentuation de la non-correspondance des profils rugueux. Le comportement d'une discontinuité est modélisée par le couplage d'un modèle élasto-plastique endommageable continu avec une résolution discrète du problème de contact/frottement (code calcul aux éléments finis Cast3M). Les résultats numériques confirment les phénomènes constatés expérimentalement. / This PhD dissertation presents a study aiming at a better understanding of cracks behavior in a geomaterial. The study focuses on the behavior of discontinuities under chemo-mechanical solicitations at the laboratory scale. The mechanical behavior under normal stress is assessed with cyclic tension-compression tests. Experimental data indicate that the inelastic deformations could be partially governed by the friction generated during the closing of the discontinuity lips, and the asperities mismatch is related to the internal stresses. The shear behavior of a rock joint chemically degraded was studied through direct shear tests. Results pointed out significant modifications for altered joints induced by: 1) the mismatch enhancement of the rough profiles of the discontinuity and, 2) the degradation of the mechanical properties of the material on both sides of the discontinuity due to the chemical attack. These experimental results have been used as input data to model the behavior of a discontinuity by the coupling of a continuous elastic-plastic damaged model with a discrete solving of the contact/friction problem. The simulations performed under Cast3M correctly represent the phenomena observed during the experimental testing program.