[pt] A indústria do petróleo realiza contínuas pesquisas para aperfeiçoar as operações de perfuração, aumentando a taxa de penetração e reduzindo o tempo não produtivo. Diversos estudos analisam o processo de corte em rocha utilizando brocas PDC (Polycrystalline Diamond Compact). Experimentos como o ensaio de cortador único simulam a interação existente entre a rocha e o cortador. Além disso, modelos numéricos têm sido criados para fazer o mesmo tipo de análise obtendo estimativas concordantes com resultados experimentais. No entanto, os ensaios experimentais geram altos custos de investimento, e por sua vez, as simulações numéricas demandam tempo muito alto para realizar análises de boa qualidade. Modelos analíticos procuram eliminar o fator custo e tempo, gerando resultados confiáveis da simulação do processo de corte, similares aos resultados das análises experimentais e numéricas. Os modelos analíticos aqui apresentados permitem estimar as forças medidas pelo cortador no processo de corte, partindo das propriedades mecânicas da rocha. Os modelos levam em conta o equilíbrio de forças no instante do corte e consideram, para o cálculo das forças, a sua geometria e as propriedades de resistência do material. A rocha utilizada no presente trabalho é um evaporito. A aplicação deste tipo de metodologia para corte em halita obriga a considerar no modelo analítico o incremento nas forças devido ao comportamento dúctil do material, à existência de deformações plásticas e à aglomeração de material na face do cortador a fim de obter uma melhor estimativa das forças de corte. Conseguem-se estimativas aceitáveis com dois dos modelos avaliados nas condições de pressões atmosféricas e altas pressões de confinamento. / [en] The oil industry carries out continuous research to improve drilling operations, to increase the penetration rate and to reduce non-productive time. Several studies analyze the rock cutting process using PDC bits (Polycrystalline Diamond Compact). Experiments with a single cutter machine measure the interaction between the rock and the cutter. Furthermore, numerical models aim to simulate the physical process and calculate results as possible consistent with experimental data. However, experimental tests are expensive and robust and numerical simulations are time consuming. Analytical models aim to reduce both cost and time factor, while providing reliable results for simulation of cutting process. The analytical models presented here allow us to estimate the forces measured on the cutter in the rock cutting process. The models take into account the balance of forces acting on the cutter face and these forces are calculated based on geometry and material properties of both cutter and rock. The rock evaluated in this work is an evaporite. The application of such type of methodology to simulate the salt rock drilling requires the analytical model to consider the increase of forces due to rock ductile behavior and the existence of plastic deformation and agglomeration of material on the cutter s face in order to obtain adequate estimation of the cutting forces. Two of the evaluated models in this work presented agreement with experimental results, both under atmospheric and high pressure conditions.

Dans ce travail est proposée une méthodologie générale de micromécanique expérimentale multi-échelle des polycristaux. Elle a été appliquée dans le cas d'un polycristal de sel gemme, qui en plus d'avoir des applications industrielles de stockage d'énergie et de déchets, constitue un matériau modèle de micromécanique présentant une déformation plastique aussi bien à l'ambiante qu'à haute température. La déformation ductile à l'échelle de la microstructure opère par la plasticité cristalline intra-granulaire traditionnelle, mais aussi des mécanismes de déformation inter-granulaires, tels que le glissement aux joints de grains. Nous avons dans un premier temps quantifié précisément la part de chacun de ces mécanismes locaux dans la déformation macroscopique du sel en se basant sur la technique de corrélation d'images numériques (CIN), obtenues au cours d'un essai de compression uni-axiale in-situ dans la chambre d'un microscope électronique à balayage (MEB). Afin d'augmenter la précision de cette quantification, des motifs spéciaux gravés aux interfaces des grains par micro-lithograhie ont été proposés. Ensuite, les observations surfaciques (par MEB) ont été étendues au cœur du matériau grâce à la micro-tomographie à rayons X et à la technique de corrélation d'images volumiques (CIV). Pour ce faire, des particules micrométriques de cuivre (3 % en volume) ont été dispersées dans le matériau lors de son élaboration, afin d'avoir un marquage local volumique adapté pour la CIV. Différentes microstructures (en termes de taille moyenne de grain) ont été considérées. De nouvelles procédures de CIV ont permis d'accéder à la répartition tridimensionnelle de la déformation ductile à l'échelle de la microstructure polycristalline avec une précision inferieure à la taille moyenne de grain. Les mécanismes de déformation observés à cœur d'échantillon sous chargement uni-axial sont cohérents avec ceux identifiés par les observations surfaciques. L'importance des mécanismes inter-granulaires dans la déformation ductile et dans l'endommagement diffus du sel a été confirmée. Une caractérisation tridimensionnelle de la microstructure par DCT (Diffraction Contrast Tomography) a été effectuée et comparée à des mesures surfaciques d'orientation cristalline par EBSD (Electron BackScattered Diffraction). Enfin, la comparaison des champs de déformation surfacique et volumique obtenus sur les mêmes échantillons a permis de retrouver les mêmes organisations et développements des localisations de déformation ductile en surface et en volume, et de les relier aux conditions de chargement et à la microstructure / We develop in this study new experimental methodologies for the multi-scale experimental investigation of the micromechanics of polycrystalline materials. These methodologies are applied to synthetic halite (NaCl), which is a convenient model polycristal due to its viscoplastic behavior at both ambient and high temperatures (350°C). In addition, halite is used for industrial applications such as underground energy and waste storage. The ductile deformation at the scale of the microstructure operates not only through conventional intra-granular plasticity, but also through inter-granular deformation mechanisms, such as grain-boundary sliding (GBS). First, we precisely quantify the relative contribution of each of these local mechanisms to the macroscopic deformation of halite. For this purpose, we apply digital image correlation (DIC) technique to high resolution images obtained during uniaxial compression tests in the chamber of a scanning electron microscope (SEM). The DIC algorithms have been modified to account for the discontinuous kinematics at grain boundries. We also propose a method to improve accuracy of GBS quantification, which consists in creating specific artificial patterns across grain-boundaries by electron beam lithography. The results show that GBS is present from the beginning of plastic deformation of the polycrystal. The 2D observations (using SEM) are complemented by 3D volume investigations using X-ray computed microtomography and Digital Volume Correlation (DVC) techniques. In order to obtain local volume markers differing in contrast (density) from NaCl and adapted to DVC, micrometric copper particles (3 % in volume) are dispersed into the material during its elaboration. Various microstructures (in terms of average grain size) are considered. New DVC protocols allow us to obtain the three-dimensional distribution of ductile deformation at the scale of the polycrystalline microstructure, with a spatial resolution finer than the average grain size. 3D and 2D local mechanical fields are compared on the same samples submitted to uniaxial compression. The strain patterns and the deformation mechanisms observed in depth of the sample are consistent with those identified by 2D observations. The results show the same organization and development of strain localization bands in relation with the loading conditions and microstructure, both at the surface and in volume. The importance of inter-granular mechanisms for the plastic deformation and diffuse damage of halite is also confirmed in 3D. Finally, in view of a further numerical model of the plasticity of the polycrystal, the three-dimensional polycrystalline microstructure is characterized by diffraction contrast tomography and compared to 2D measurements obtained by electron BackScattered diffraction

Dans ce travail est proposée une méthodologie générale de micromécanique expérimentale multi-échelle des polycristaux. Elle a été appliquée dans le cas d'un polycristal de sel gemme, qui en plus d'avoir des applications industrielles de stockage d'énergie et de déchets, constitue un matériau modèle de micromécanique présentant une déformation plastique aussi bien à l'ambiante qu'à haute température. La déformation ductile à l'échelle de la microstructure opère par la plasticité cristalline intra-granulaire traditionnelle, mais aussi des mécanismes de déformation inter-granulaires, tels que le glissement aux joints de grains. Nous avons dans un premier temps quantifié précisément la part de chacun de ces mécanismes locaux dans la déformation macroscopique du sel en se basant sur la technique de corrélation d'images numériques (CIN), obtenues au cours d'un essai de compression uni-axiale in-situ dans la chambre d'un microscope électronique à balayage (MEB). Afin d'augmenter la précision de cette quantification, des motifs spéciaux gravés aux interfaces des grains par micro-lithograhie ont été proposés. Ensuite, les observations surfaciques (par MEB) ont été étendues au cœur du matériau grâce à la micro-tomographie à rayons X et à la technique de corrélation d'images volumiques (CIV). Pour ce faire, des particules micrométriques de cuivre (3 % en volume) ont été dispersées dans le matériau lors de son élaboration, afin d'avoir un marquage local volumique adapté pour la CIV. Différentes microstructures (en termes de taille moyenne de grain) ont été considérées. De nouvelles procédures de CIV ont permis d'accéder à la répartition tridimensionnelle de la déformation ductile à l'échelle de la microstructure polycristalline avec une précision inferieure à la taille moyenne de grain. Les mécanismes de déformation observés à cœur d'échantillon sous chargement uni-axial sont cohérents avec ceux identifiés par les observations surfaciques. L'importance des mécanismes inter-granulaires dans la déformation ductile et dans l'endommagement diffus du sel a été confirmée. Une caractérisation tridimensionnelle de la microstructure par DCT (Diffraction Contrast Tomography) a été effectuée et comparée à des mesures surfaciques d'orientation cristalline par EBSD (Electron BackScattered Diffraction). Enfin, la comparaison des champs de déformation surfacique et volumique obtenus sur les mêmes échantillons a permis de retrouver les mêmes organisations et développements des localisations de déformation ductile en surface et en volume, et de les relier aux conditions de chargement et à la microstructure / We develop in this study new experimental methodologies for the multi-scale experimental investigation of the micromechanics of polycrystalline materials. These methodologies are applied to synthetic halite (NaCl), which is a convenient model polycristal due to its viscoplastic behavior at both ambient and high temperatures (350°C). In addition, halite is used for industrial applications such as underground energy and waste storage. The ductile deformation at the scale of the microstructure operates not only through conventional intra-granular plasticity, but also through inter-granular deformation mechanisms, such as grain-boundary sliding (GBS). First, we precisely quantify the relative contribution of each of these local mechanisms to the macroscopic deformation of halite. For this purpose, we apply digital image correlation (DIC) technique to high resolution images obtained during uniaxial compression tests in the chamber of a scanning electron microscope (SEM). The DIC algorithms have been modified to account for the discontinuous kinematics at grain boundries. We also propose a method to improve accuracy of GBS quantification, which consists in creating specific artificial patterns across grain-boundaries by electron beam lithography. The results show that GBS is present from the beginning of plastic deformation of the polycrystal. The 2D observations (using SEM) are complemented by 3D volume investigations using X-ray computed microtomography and Digital Volume Correlation (DVC) techniques. In order to obtain local volume markers differing in contrast (density) from NaCl and adapted to DVC, micrometric copper particles (3 % in volume) are dispersed into the material during its elaboration. Various microstructures (in terms of average grain size) are considered. New DVC protocols allow us to obtain the three-dimensional distribution of ductile deformation at the scale of the polycrystalline microstructure, with a spatial resolution finer than the average grain size. 3D and 2D local mechanical fields are compared on the same samples submitted to uniaxial compression. The strain patterns and the deformation mechanisms observed in depth of the sample are consistent with those identified by 2D observations. The results show the same organization and development of strain localization bands in relation with the loading conditions and microstructure, both at the surface and in volume. The importance of inter-granular mechanisms for the plastic deformation and diffuse damage of halite is also confirmed in 3D. Finally, in view of a further numerical model of the plasticity of the polycrystal, the three-dimensional polycrystalline microstructure is characterized by diffraction contrast tomography and compared to 2D measurements obtained by electron BackScattered diffraction

Polycrystalline geological materials are not normally single phase materials and commonly contain second phases which are known to influence the grain size and mechanical properties of bulk material. Despite the well documented significance of second phases, there are relatively few detailed systematic experimental studies of the effect of second phases on isostatic high temperature grain growth in geological materials. Grain growth is a process that is fundamental to our understanding of how rocks behave in the lower crust / upper mantle where grain size is considered to play an important role in the localization of deformation in addition to determining the strength of materials at these pressure and temperature conditions. Furthermore, the effect that the spatial distribution and grain size of the second phases have on the mechanical properties of rocks is generally acknowledged, but it is not well constrained. Spatial variation is particularly significant in geological systems where a strength contrast exists between phases. With these two things in mind, a two-part study is presented in which the influence of a pore second phase on the microstructural evolution of halite during grain growth (Part I), and the influence of a calcite second phase on the mechanical behaviour of two phase calcite + halite aggregates (Part II), is investigated. In Part I, high temperature (330 °-600 °C), high confining pressure (200 MPa) isostatic grain growth experiments were carried out on 38-125 μm reagent grade halite (99.5%+ NaCl) powder over durations of 10 secs up to 108 days. After hot-pressing, the halite displays a foam texture. Some porosity remained along the grain boundaries, the size and distribution of which appears to impact significantly on the resulting grain size, growth mechanism and kinetics of halite grain growth. Halite grain growth was found to be well described by the normal grain growth equation: d^(1/n)-d0^(1/n)=k0(t-t0)exp(-H/RT) where t is the duration of the growth period, t0 is the time at which normal growth begins, d is the grain size, d0 is the grain size at t0, k0 is a constant, H is the activation enthalpy for the growth controlling process, R is the universal gas constant,T is temperature and n is a growth constant. At 330 °-511 °C, the data is best described by n = 0.25 indicating growth controlled by surface diffusion around pores that lie on the grain boundaries. An activation enthalpy of 122±34 kJ/mol was obtained using the grain size data from these data sets. At 600 °C the data is best described by n = 0.5, suggesting that a transition to interface controlled growth takes place between 511 °C and 600 °C. To investigate the impact of porosity, the Zener parameter (Z = pore size/pore volume fraction) was determined for individual grains in 10 samples. A general trend of increasing with increasing halite grain size is observed, indicating pore elimination keeps pace with pore accumulation in the growing grains. In some samples, the largest grains display a decrease in the Zener parameter corresponding with an increase in pore volume fraction. These grains are interpreted as having experienced a short-lived, abnormal growth phase shortly after t0 during which pore accumulation outpaced pore elimination. A model of pore controlled grain growth is proposed with a view to explaining these observations. In Part II, calcite + halite aggregates of constant volume fraction (0.60 calcite : 0.40 halite) and varying calcite clast size (6 μm 361 μm) were axially deformed to <1% bulk strain at room temperature in a neutron diffraction beamline. Elastic strain and stress in each phase was determined as a function of load from the neutron diffraction data. The strain (and stress) behaviour correlates well with the microstructural parameters: 1) halite mean free path and 2) calcite contiguity. Both phases behaved elastically up to aggregate axial stresses of 20-37 MPa, above these stresses the halite yielded plastically while the calcite remained elastic. Once yielding began, the rate of enhanced load transfer from halite to calcite with increasing applied load decreased with halite mean free path and increased calcite with contiguity. A Hall-Petch relationship between halite mean free path and aggregate yield stress was observed.

The general temperature range for THEREDA is currently limited to 0 to about 110°C. For the important electrolyte NaCl there are thermodynamic data available to 200°C and above. To cover this larger temperature range for the Pitzer coefficients, a refit of the temperature functions of Greenberg, J. P. and Møller, N. (Geochim. Cosmochim. Acta 53 (1989) 2503-2518) is presented. A corresponding function for the solubility constant of NaCl is deduced from IUPAC recommended data. The data set for NaCl, thus extended in its range of validity up to 200°C, is implemented in THEREDA.

[pt] A importância do sal em diversas atividades humanas tem acompanhado as fases principais da civilização. Aplicações estratégicas e inovadoras envolvendo rochas salinas são planejadas até os dias atuais, tais como barreiras geológicas para abandono de poços e cavernas de estocagem para novas fontes de energia ou descarbonização. Esta tese foca no comportamento geomecânico do sal com atenção especial à fluência, dilatância, efeitos térmicos e seus impactos no comportamento hidráulico. Modelos deram suporte ao desenvolvimento de metodologias para avaliação de condições de integridade e estanqueidade de projetos estratégicos no contexto de energia. Eles incluem o abandono de poços do pré-sal, cavernas de sal e sal como rocha capeadora de reservatórios carbonáticos. Simulações numéricas avançadas utilizando o framework GeMA investigaram cenários representativos de cada projeto. Para tanto, modelos constitutivos de fluência, condições de contorno customizadas e variáveis de saída específicas foram implementados. Dentre os modelos de fluência, o EDMT foi desenvolvido no contexto desta pesquisa de doutorado, com foco no sal brasileiro. Os estudos de caso conduziram a observações importantes. Um poço do pré-sal pode fechar completamente por fluência após a remoção do revestimento. A redução da pressão e o aquecimento do poço aceleraram seu fechamento de modo significativo. No cenário mais crítico, a permeabilidade final foi ligeiramente superior a 100 vezes o valor inicial. Uma caverna de sal pode suportar mecanicamente ciclos de pressão causados por um esquema contingencial de fornecimento de hidrocarbonetos, embora uma permeabilidade final de 6,5 vezes o valor inicial tenha sido observada. Na geomecânica de reservatórios, a contribuição da fluência da rocha capeadora na subsidência é pequena e irreversível mesmo que a pressão do reservatório seja recuperada. As mudanças na permeabilidade foram sutis apesar da contribuição da fluência do sal e da variação de pressão do reservatório. A revisão da literatura, os modelos de fluência, as metodologias de análise, as funcionalidades incorporadas ao framework e as discussões motivadas pelos estudos de caso representam o valor agregado da tese para a comunidade científica e para a indústria no que tange ao aproveitamento estratégico de rochas salinas. / [en] The importance of salt in many human activities has accompanied the main phases of civilization. Strategic and innovative applications in salt rocks are planned until the present day, such as geological barriers for well abandonment and storage caverns for new energy sources or decarbonization. This thesis focuses on the geomechanical behavior of salt with special regards to creep, dilation, thermal effects and their impact on the hydraulic behavior. Models have supported the development of methodologies to assess integrity and tightness conditions of strategic projects in the context of energy. These include Pre-salt well abandonment, salt caverns and salt as caprock of carbonate reservoirs. Advanced numerical simulations using the framework GeMA have investigated representative scenarios of each project. To this end, creep constitutive models, customized boundary conditions and specific output variables have been implemented. Among the creep models, the EDMT has been developed in the context of this doctoral research, focusing on Brazilian salt. The case studies have led to important findings. A Pre-salt well can close completely by creep after casing removal. Pressure reduction and well heating have accelerated closure significantly. In the most critical scenario, the final permeability was slightly higher than 100 times the initial value. A salt cavern can mechanically support pressure cycles caused by a contingency hydrocarbon supply scheme; however, a final permeability of 6.5 times the initial value has been noticed. In reservoir geomechanics, the caprock creep contribution in the subsidence is small and irreversible even if the reservoir pressure is recovered. Permeability changes have been subtle despite the creep contribution and the reservoir pressure variation. The literature review, the creep models, the analysis methodologies, the capabilities incorporated into the framework and the discussions motivated by the case studies represent the added value of the thesis to the scientific community and industry regarding the strategic use of salt rocks.

Afin d'étudier le rôle de l'humidité dans la déformation du sel gemme, des essais utilisant la microcellule développée au Centre de Géologie de l'Ingénieur ont été conduits sur des échantillons de sel laiteux et de sel phénoblastique du Bassin Bressan ainsi que sur des échantillons de sel de dôme provenant de la mine d'Asse (Allemagne). Le principe de la méthode utilisée est de suivre visuellement, lors des essais effectués, l'évolution texturale des échantillons sous des conditions de contrainte, température et humidité imposées. Une augmentation même faible du degré d'humidité relative se traduit toujours par une phase de fluage transitoire rapide suivie d'une phase de fluage stationnaire à vitesse de déformation constante. La vitesse de déformation lors de cette phase de fluage stationnaire est généralement supérieure à celle de la phase de fluage stationnaire qui précède l'élévation du degré d'humidité. La texture et la composition de l'échantillon ainsi que sa réaction vis-à-vis du couple température-humidité imposé déterminent la prédominance d'un des micromécanismes de déformation possibles. D'un point de vue microstructural, le contenu des cristaux de halite en inclusions fluides et/ou solides exerce une grande influence sur leur ductilité. On montre que le sel laiteux riche en inclusions fluides est plus ductile que le sel de dôme dont les cristaux contiennent des inclusions solides. Au niveau des joints de grains, l'humidité s'adsorbe ou se condense permettant le déclenchement de certains mécanismes de déformation spécifiques. Selon la morphologie et l'état de surface de ces joints on assiste à des mécanismes de lubrification et de glissement (cas du sel de dôme) ou des mécanismes de cisaillement et de microstylolitisation (cas du sel laiteux). Par ailleurs, les films de saumures qui se reconstituent au niveau des joints favorisent la thermomigration des inclusions fluides d'un cristal de halite à un autre à travers ces joints saturés. Dans le sel phénoblastique 1'anhydrite contenue dans la matrice carbonato-sulfatée microporeuse s'hydrate en gypse sous l'action du couple température-humidité. Cette transformation s'accompagne d'un gonflement important qui se traduit par la fissuration prononcée des plages non halitiques ce qui peut entraîner une dégradation notable du matériau. En prenant en compte les trois paramètres essentiels qui conditionnent le fluage du sel gemme: la texture, la température (avec et sans gradient) et l'humidité, l'étude expérimentale tend à reconstituer de manière réaliste l'état des conditions susceptibles de se réunir à proximité d'une galerie de stockage de déchets radioactifs. Par conséquent elle permet d'avancer des arguments nécessaires pour aider à la prévision du comportement d'un massif salifère à long terme.

The high affinity, ATP-dependent K+ uptake system KdpFABC of Halobacterium salinarum, is highly induced under K+ limitation. In contrast to the well-characterized Kdp system in Escherichia coli, in which the kdpFABC genes are transcriptionally regulated by the sensor kinase/response regulator system KdpD/KdpE, transcriptional regulation of the kdp genes in H. salinarum was unknown due to the absence of halobacterial homologues of KdpD/KdpE. Furthermore, the physiological relevance of the KdpFABC K+ uptake system of H. salinarum was puzzling, since hypersaline habitats usually comprise K+ concentrations which do not induce kdp expression. In order to analyze the regulation of kdp gene expression, it was essential to gain information about the transcriptional unit(s) involved. Northern blotting, primer extension analysis and real-time RT-PCR revealed the presence of a polycistronic leaderless kdpFABCQ transcript with a putative kdp terminator or at least a potential mRNA processing site downstream of kdpQ. Furthermore, promoter truncation studies verified the so far only predicted basal transcription elements together with an upstream-located operator sequence. Since deletions of this putative operator sequence did not lead to a constitutive expression, a further component has to be involved in the regulation of the kdpFABCQ genes. However, truncation and scanning mutagenesis analyses of the kdp promoter as well as translational fusions of a halophilic beta-galactosidase to the kdp promoter excluded an additional regulatory element up- or downstream of the basal transcription elements and in the kdp-coding region. These results lead to speculations of multiple basal transcription factors to be involved. Furthermore, an inducible expression vector (shuttle vector) was constructed based on the promoter of the kdpFABCQ operon due to its, K+-sensitive features. Inducible expression systems are yet not available for H. salinarum. The resulting, replicating vector pKIX is functional and enables a K+-dependent expression from the kdp promoter with rather high induction ratios of 50-fold. Expression levels could further be improved by plasmid- and additional chromosomally encoded kdpQ and mutations generated in the kdp promoter. Since transcript levels from pKIX were found to be independent of differential target genes, the general application of pKIX as an inducible expression system is strongly supported and pKIX could, thus, be made accessible to the scientific community. To decipher the physiological relevance of the halobacterial Kdp system, H. salinarum was encountered to desiccation stress and salt crystal (halite) entombment. Halite crystals grown under non-inducing K+ concentrations with entombed strains of H. salinarum and H. salinarum deleted in the kdpFABCQ genes revealed a significantly reduced survival rate of the deletion strain upon recultivation. Additionally, a kdpFABCQ-inducing desiccation stress could already be determined on agar plates under non-limiting K+ concentrations. Furthermore, the cell morphology of H. salinarum entrapped in halite crystals resembled that of H. salinarum grown under K+-limiting conditions. Therefore, the Kdp system promotes survival of H. salinarum under desiccation stress. Furthermore, the Kdp system could be identified as at least one of the systems important for long-term survival of H. salinarum in halite.