Le polymer flooding est une des techniques de récupération assistée des hydrocarbures (RAH) ; elle consiste à injecter une solution de polymères de forte masse moléculaire afin de déplacer plus efficacement le pétrole emprisonné dans la roche. Cependant, une limite importante de cette technique est la possible dégradation mécanique des polymères au cours de l'injection et dans le réservoir, due à une scission des chaînes macromoléculaires induite par l’écoulement. Ce travail de thèse a pour objectif de mieux comprendre les mécanismes et scénarios de scission, mais aussi leur impact sur le procédé de polymer flooding. Nous nous sommes intéressés au seuil de dégradation mécanique de solutions de poly(oxyde d’éthylène) et de de polyacrylamide partiellement hydrolysé, pour différents régimes de concentration (solutions diluées et semi-diluées) en régime laminaire et inertiel, et pour des solvants de différentes qualités. L’étude de la dégradation mécanique des solutions et de leur impact sur les propriétés rhéologiques a été menée à l’aide de différents dispositifs de dégradation et de différents rhéomètres, dont un dispositif microfluidique en élongation ; ces techniques de mesure ont été combinées à des mesures de distribution de masses moléculaires par chromatographie d’exclusion stérique couplée à la diffusion de lumière. L’étude montre en premier lieu qu’une composante élongationnelle est indispensable pour dégrader les chaînes macromoléculaires en solution. Les résultats mettent aussi clairement en évidence que les mécanismes de dégradation sont très différents en régime dilué et semi-dilué. En régime dilué, la dégradation mécanique des solutions de polymères est indépendante du régime d’écoulement et affecte préférentiellement les macromolécules de fortes masses, avec une scission en milieu de chaîne. En revanche, en régime semi-dilué, la dégradation mécanique dépend du régime de l’écoulement : en écoulement laminaire, la dégradation est gouvernée par le réseau d’enchevêtrements et la scission des chaînes est aléatoire, tandis qu’en régime inertiel, les chaînes se dégradent comme en régime dilué, avec le même scénario de scission en milieu de chaîne. Par ailleurs, les résultats montrent que les propriétés rhéologiques en élongation peuvent être très fortement impactées par la dégradation mécanique. Enfin, les résultats de l’étude préliminaire des propriétés d’injectivité dans un milieu poreux d’une solution de polymère semi-diluée faiblement dégradée montrent que la dégradation mécanique améliore l’injectivité du polymère aux abords du puits. / Polymer flooding is a technique used in enhanced oil recovery; it consists in injecting high molecular weight polymer solutions in order improve oil sweep efficiency in the reservoir. However, polymer flooding is challenged by possible mechanical degradation of polymer solutions during injection and in the reservoir, due to the flow induced scission of macromolecules. This work aims at better understanding the scission mechanisms and scenarios, but also their impact on polymer flooding. We investigated the onset of mechanical degradation of poly(ethylene oxide) and partially hydrolysed polyacrylamide solutions, for different concentration regimes (dilute and semi-dilute regimes), under laminar or inertial conditions, but also under good or bad solvent conditions. The study of mechanical degradation of polymer solutions and their impact on the rheological properties was performed using different degradation devices and different rheometers, including a microfluidic extensional device; these investigation techniques were combined with measurements of the molecular weight distributions using size exclusion chromatography coupled with light scattering experiments. The study first shows that an extensional component is needed to get a mechanical degradation of polymer chains. The results also clearly show that the degradation mechanisms are very different in dilute and semi-dilute regime. In dilute regime, the mechanical degradation of polymer solutions does not dependent on flow regime and mainly affects the macromolecules with high molecular weights, with a mid-chain scission scenario. On the other hand, in semi-dilute regime, mechanical degradation depends on flow regime: in laminar flows, degradation is governed by the entanglement network and chain scission is random, whereas in inertial flows, chain degradation is similar to that observed in dilute regime, with the same mid-chain scission scenario. Besides, the results show that the extensional rheological properties can be very strongly affected by mechanical degradation. At last, the results of a preliminary study of the injectivity of a slightly degraded semi-dilute polymer solution in porous media show that mechanical degradation improves polymer injectivity near the wellbore.

Este trabalho caracterizou os siltitos do Grupo Itararé, rocha branda proveniente da amostragem de pedreira localizada nas proximidades de futuro empreendimento brasileiro, o Trem de Alta Velocidade. Objetivou entender as causas da pronunciada e rápida alteração da rocha intacta, e simular, em condições controladas de laboratório, a degradação hidromecânica causada pela simples variação da umidade relativa do ar. Para tal, estabeleceu-se técnica de amostragem de testemunhos por meio da extração via seca com ar-comprimido, e processo de intemperismo artificial, composto por 4 ciclos de 2 etapas (secagem e umedecimento). O processo se deu em dessecadores, sendo a variação da umidade ocasionada pela técnica do vapor e sílica gel. O acompanhamento da degradação dos corpos de prova efetuou-se com duas técnicas não-destrutivas de propagação de ondas: o pulso ultrassônico e a excitação por impulso (sistema Sonelastic). Em paralelo, realizou-se a caracterização geotécnica dos siltitos em umidade natural, com ensaios mineralógicos, físicos, físico-mecânicos, físico-químicos e de alteração laboratorial. Por meio desta metodologia, foi possível estimar as minorações do módulo de deformabilidade e da resistência, além das causas físico-químicas da degradação. / This work characterized the siltstones of the Itararé Group, a soft rock sampled in a quarry located near a future Brazilian venture, the High Speed Train. It aims at understanding the causes of the pronounced and fast changes of the intact rock, and simulate in controlled laboratory conditions the hydro degradation process caused by simple variation of relative air humidity. Dry sampling technique with compressed air was used to extract samples from blocks, and the process of artificial weathering consisted on 4 cycles of 2 steps (drying and wetting). The process occurred in desiccators, where moisture variation was caused by the vapor technique and silica gel. The monitoring of the specimens degradation was performed with two non-destructive wave propagation techniques: the ultrasonic pulse and the impulse excitation (Sonelastic system). A geotechnical characterization of the siltstones in natural moisture condition was made in parallel, consisting on mineralogical, physical, physical-mechanical, physical-chemical and durability tests. By this methodology, it was possible to estimate the mitigation of the deformability modulus and strength besides the physical- chemical causes of degradation.

Le développement des lubrifiants est un véritable levier pour les constructeurs automobiles et les pétroliers pour minimiser les pertes d'énergie dues aux frottements dans les moteurs. La viscosité est le principal paramètre sur lequel les formulateurs peuvent jouer pour abaisser les frottements. Cette thèse porte sur l'étude du rôle et des actions des additifs améliorants de viscosité (AVI) dans les lubrifiants moteur. L'objectif de cette thèse est de corréler l'étude portée à l'échelle moléculaire aux propriétés macroscopiques ainsi qu'aux performances des lubrifiants moteur pour pouvoir orienter les formulateurs vers une ou des molécules cibles qui permettront de répondre le mieux possible à ces problématiques. Ce travail est consacré à des poly-diène-styrène hydrogénés (P-diène-SH) et des copolymères éthylène propylène (EPC). Dans un premier temps, des études structurales des polymères AVI et rhéologiques des solutions ont permis de mettre en évidence l'influence des différentes chimies et structures des polymères sur leurs propriétés rhéologiques. Cette étude a porté sur une large gamme de températures (-20 à +135°C), taux de cisaillement (0 à 107s-1) et concentrations permettant de caractériser la configuration des polymères dans des conditions correspondant à l’application. Dans un second temps, ces propriétés rhéologiques ont été corrélées avec les coefficients de frottement et les épaisseurs de film centrales dans un contact de type sphère/plan en tribologie.Enfin, la capacité des chaînes de ces polymères à se rompre sous la contrainte d’un fort taux de cisaillement en écoulement pulsé ou continu a été étudiée et reliée à la configuration des polymères AVI en solution ainsi que leurs structures. L’ensemble de ces données a été utilisé pour proposer une structure chimique et une architecture présentant des propriétés AVI, une bonne résistance mécanique et un comportement tribologique satisfaisant. / The development of lubricants is a real challenge for the automotive and the petroleum industries to reduce the energy losses in engines due to frictions. The viscosity is the main parameter that the lubricant formulators can vary to reduce the frictions. This PhD deals with the role and mode of actions of viscosity modifier polymers (VM polymers) in lubricants.The purpose of this PhD is to correlate the study at the molecular scale with the macroscopic properties and the lubricant performances in order to orient the formulators towards one or several target molecules which could present the best properties.This work consisted in characterizing hydrogenated Poly-diene-styrene (P-diene-SH) and ethylene-propylene-copolymers (EPC).First, studies on the structure of VM polymers and on rheological properties of the solutions have shown the influence of the different chemical structures and polymer architectures on their rheological properties. This study was carried out on a large scale of temperatures (-20 à +135°C), shear rates (0 à 107s-1) and concentrations leading to characterizations under conditions corresponding to practical conditions.Secondly, these rheological properties were correlated with frictions coefficients and the film thickness in a sphere/plate contact in tribology.Finally, the ability of the polymer chains to break when a high shear rate was applied in a continuous or pulsed flow was studied and related to the chains configurations of the VM polymer and their structure.All these data were further used to propose a chemical structure and a polymer architecture leading to viscosity improved properties, a good resistance to degradation and a satisfactory behavior in tribology.

Este trabalho caracterizou os siltitos do Grupo Itararé, rocha branda proveniente da amostragem de pedreira localizada nas proximidades de futuro empreendimento brasileiro, o Trem de Alta Velocidade. Objetivou entender as causas da pronunciada e rápida alteração da rocha intacta, e simular, em condições controladas de laboratório, a degradação hidromecânica causada pela simples variação da umidade relativa do ar. Para tal, estabeleceu-se técnica de amostragem de testemunhos por meio da extração via seca com ar-comprimido, e processo de intemperismo artificial, composto por 4 ciclos de 2 etapas (secagem e umedecimento). O processo se deu em dessecadores, sendo a variação da umidade ocasionada pela técnica do vapor e sílica gel. O acompanhamento da degradação dos corpos de prova efetuou-se com duas técnicas não-destrutivas de propagação de ondas: o pulso ultrassônico e a excitação por impulso (sistema Sonelastic). Em paralelo, realizou-se a caracterização geotécnica dos siltitos em umidade natural, com ensaios mineralógicos, físicos, físico-mecânicos, físico-químicos e de alteração laboratorial. Por meio desta metodologia, foi possível estimar as minorações do módulo de deformabilidade e da resistência, além das causas físico-químicas da degradação. / This work characterized the siltstones of the Itararé Group, a soft rock sampled in a quarry located near a future Brazilian venture, the High Speed Train. It aims at understanding the causes of the pronounced and fast changes of the intact rock, and simulate in controlled laboratory conditions the hydro degradation process caused by simple variation of relative air humidity. Dry sampling technique with compressed air was used to extract samples from blocks, and the process of artificial weathering consisted on 4 cycles of 2 steps (drying and wetting). The process occurred in desiccators, where moisture variation was caused by the vapor technique and silica gel. The monitoring of the specimens degradation was performed with two non-destructive wave propagation techniques: the ultrasonic pulse and the impulse excitation (Sonelastic system). A geotechnical characterization of the siltstones in natural moisture condition was made in parallel, consisting on mineralogical, physical, physical-mechanical, physical-chemical and durability tests. By this methodology, it was possible to estimate the mitigation of the deformability modulus and strength besides the physical- chemical causes of degradation.