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International audience; One of the challenges in the study of foam transport in 3D porous media is having an adequate spatial and temporal resolution, to get a better understanding of the local phenomenon at the pore scale in a non-destructive way. We present an experimental study in which ultra fast X-Ray microtomography is used to characterize the foam trapping while the foam is flowing in a 3D porous medium. A preformed aqueous foam is injected into a rotating cell containing a 3D granular medium made of silica grains. The use of rotating seals allows the cell to rotate continuously at the rate of one revolution per second, compatible with the fast X-ray tomography at SOLEIL synchrotron. We visualize the foam flow and track the trapping of bubbles with an acquisition time of about one second and a spatial resolution of a few microns (pixel size of one micron). This allows us to extract characteristics and reliable statistics about trapped bubbles inside the granular medium and to observe their local behavior. With this setup and technique we access to the dynamics of foam trapping during the flow and the texture variations of the foam in the trapped zones. These local trapping events are well correlated with the macroscopical measurement of the pressure gradient over the cell.

International audience; In this study, three clinopyroxene-enriched upper mantle xenoliths, petrographically classified as wehrlite,were investigated from the Nógrád–Gömör Volcanic Field with the use of X-ray microtomography. Our main goal was toquantify the volume of the glass phase and the vesicles to reveal their three-dimensional distribution. Among the studiedwehrlite xenoliths, one is weakly and two are strongly metasomatized. The two latter wehrlite xenoliths are characterizedby higher modal amount of glass and vesicles, which suggests a genetic connection between glass and concomitantvesicles, and the metasomatic agent. The glass, which was a melt at mantle conditions, forms an interconnected network.This may explain the presence of the electromagnetic anomaly with high electrical conductivity beneath the study area.Our study contributes to the better understanding of melt migration and its metasomatic effect in the lithospheric mantlebeneath monogenetic volcanic fields

Summary Waterflooding is often inefficient in carbonate reservoirs because of the presence of fractures and unfavorable wettability. Oil recovery can be improved by enhancing the following drive mechanisms: Capillary imbibition with wettability modifiers Viscous drive by increasing the pressure gradient in the fracture network Water/oil gravity drainage with low-interfacial-tension (IFT) surfactant formulations that also reduce oil trapping This paper presents an experimental approach that evaluates different chemical-enhanced-oil-recovery (EOR) alternatives on the basis of one or several of the three aforementioned recovery mechanisms. The experiments consist of injecting an aqueous chemical solution or a foam containing chemical additives into an artificially fractured carbonate core. The imbibition is monitored with a recent computed-tomography (CT) scanner allowing the local quantitative monitoring of three phases, including accurate quantification of matrix oil recovery. This paper is mainly focused on the impacts of foaming agents and wettability modifiers (WMs), implemented separately or jointly. The experiments have been conducted on several cores of different permeability, resulting in various permeability contrasts between matrix and fracture. A major result concerns the kinetics of oil recovery by chemical additives that is greatly increased when a viscous drive is applied across the matrix medium by means of the circulation of foam in the fracture. Experiments in fractured cores of different permeabilities indicate that foam does not penetrate the matrix, but drives the chemical aqueous phase into the matrix because of the generated pressure gradient. Detailed analysis of oil-mobilization dynamics is provided. These foam-flow experiments are compared with a former chemical imbibition test on a nonfractured core for further insight into the role played by viscous forces. The comparison of tested recovery scenarios leads to conclusions regarding optimal chemical-EOR strategies for naturally fractured carbonate reservoirs with poor secondary-recovery prognosis.

International audience; Subduction of carbonated crust is widely believed to generate a flux of carbon into the base of the continental lithospheric mantle, which in turn is the likely source of widespread volcanic and non-volcanic CO2 degassing in active tectonic intracontinental settings such as rifts, continental margin arcs and back-arc domains. However, the magnitude of the carbon flux through the lithosphere and the budget of stored carbon held within the lithospheric reservoir are both poorly known. We provide new constraints on the CO2 budget of the lithospheric mantle below the Pannonian Basin (Central Europe) through the study of a suite of xenoliths from the Bakony-Balaton Highland Volcanic Field. Trails of secondary fluid inclusions, silicate melt inclusions, networks of melt veins, and melt pockets with large and abundant vesicles provide numerous lines of evidence that mantle metasomatism affected the lithosphere beneath this region. We obtain a quantitative estimate of the CO2 budget of the mantle below the Pannonian Basin using a combination of innovative analytical and modeling approaches: (1) synchrotron X-ray microtomography, (2) NanoSIMS, Raman spectroscopy and microthermometry, and (3) thermodynamic models (Rhyolite-MELTS). The three-dimensional volumes reconstructed from synchrotron X-ray microtomography allow us to quantify the proportions of all petrographic phases in the samples and to visualize their textural relationships. The concentration of CO2 in glass veins and pockets ranges from 0.27 to 0.96 wt.%, higher than in typical arc magmas (0–0.25 wt.% CO2), whereas the H2O concentration ranges from 0.54 to 4.25 wt.%, on the low end for estimated primitive arc magmas (1.9–6.3 wt.% H2O). Trapping pressures for vesicles were determined by comparing CO2 concentrations in glass to CO2 saturation as a function of pressure in silicate melts, suggesting pressures between 0.69 to 1.78 GPa. These values are generally higher than trapping pressures for fluid inclusions determined by Raman spectroscopy and microthermometry (0.1–1.1 GPa). The CO2/silicate melt mass ratios in the metasomatic agent that percolated through the lithospheric mantle below the Pannonian Basin are estimated to be between 9.0 and 25.4 wt.%, values consistent with metasomatism either by (1) silicate melts already supersaturated in CO2 before reaching lithospheric depths or (2) carbonatite melts that interacted with mantle peridotite to generate carbonated silicic melts. Taking the geodynamical context of the Pannonian Basin and our calculations of the CO2/silicate melt mass ratios in the metasomatic agent into account, we suggest that slab-derived melts initially containing up to 25 wt.% of CO2 migrated into the lithospheric mantle and exsolved CO2–rich fluid that became trapped in secondary fluid inclusions upon fracturing of the peridotite mineral matrix. We propose a first-order estimate of 2000 ppm as the minimal bulk CO2 concentration in the lithospheric mantle below the Pannonian Basin. This transient carbon reservoir is believed to be degassed through the Pannonian Basin due to volcanism and tectonic events, mostly focused along the lithospheric-scale regional Mid-Hungarian shear Zone.

Foam has long been used as a mobility control agent in Enhanced Oil Recovery (EOR) processes to enhance sweep efficiency and overcome gravity segregation, viscous fingering and gas channeling, which are gas-related problems when the latter is injected alone in the reservoir. However, the systematic use of foam in reservoir engineering requires more in-depth knowledge of its dynamics in porous media. The literature shows two types of experimental approaches based either on petrophysical studies carried out on 3D porous systems and based on pressure measurements, or on microfluidic studies that allow direct visualization of foam flow but are limited to 1D or 2D model systems. The research investigated in this thesis aims to bridge the gap between these two approaches. The proposed strategy is to characterize in situ the foam flow in 3D porous media with techniques providing a wide range of temporal and spatial resolutions. A coreflood setup giving access to classical petro-physical measurements was developed and then coupled to different observation cells designed specifically for each characterization instrument. First, an X-ray CT scanner was used to describe and visualize the foam flow at the core scale. The rheological behavior of foam on this scale was studied as a function of the injection conditions such as gas velocity and foam quality. Secondly, Small Angle Neutron Scattering (SANS) was used to probe the foam structure in situ during the flow, on a wide length scale, up to three orders of magnitude in size. In situ foam texture (size and density of bubbles and lamellae) was measured for different foam qualities and at different propagation distances from the injection point. A comparison to the geometric characteristics of the porous medium was also realized. Thirdly, High Resolution Fast X-ray Micro-tomography on a Synchrotron was used to visualize the foam flow at the pore scale. This allowed to confirm visually some foam characteristics measured with SANS and to investigate on local intermittent gas trapping and mobilization. This study is an important step in the multi-scale characterization of foam flow in 3D porous media and provides some answers to certain generally accepted assumptions., L’utilisation de la mousse en récupération assistée du pétrole (Enhanced Oil Recovery, EOR) présente un avantage indéniable par rapport à l’injection du gaz seul pour pallier les problèmes de ségrégation gravitaire et de digitations visqueuses. Son utilisation systématique en ingénierie du réservoir nécessite des connaissances plus approfondies sur son comportement en milieu poreux. La littérature montre deux types d’approches expérimentales basées soit sur des études pétrophysiques effectuées sur des systèmes poreux 3D et basées sur des mesures de pressions intégrées sur l’ensemble du milieu poreux, soit sur des études micro-fluidiques qui permettent une visualisation directe de l’écoulement mais qui sont limitées à des systèmes modèles dans des géométries à 1 ou 2 dimensions. L’objectif de cette thèse est de faire le pont entre ces deux approches. La stratégie proposée consiste à caractériser in situ l’écoulement de la mousse dans des milieux poreux 3D à différentes échelles, en utilisant des techniques complémentaires permettant d’accéder à une large gamme de résolutions spatiale et temporelle. Un environnement instrumenté donnant accès aux mesures pétro-physiques classiques a été développé puis couplé à différentes cellules d’observation conçues spécifiquement pour chaque instrument de caractérisation. Dans un premier temps, un scanner X a été utilisé pour décrire et visualiser les écoulements de la mousse à l’échelle de la carotte. La rhéologie de la mousse à cette échelle a pu être étudiée en fonction des conditions d’injections comme la vitesse interstitielle du gaz et la qualité de mousse. Dans un deuxième temps, la technique de diffusion des neutrons aux petits angles (SANS) a permis de sonder la texture de la mousse en écoulement sur trois ordres de grandeurs en taille. Des informations in situ sur la texture de la mousse en écoulement (taille et densité des bulles et des lamelles) ont pu être mesurées pour différentes qualités de mousse puis en fonction de la distance au point d’injection. Une comparaison avec les caractéristiques géométriques du milieu poreux a également été effectuée. Dans un troisième temps, la micro-tomographie X rapide haute résolution sur Synchrotron a été utilisée pour visualiser la mousse en écoulement à l’échelle du pore. Cette technique a permis de confirmer de visu certaines caractéristiques de la mousse mesurées par SANS et de décrire en sus les effets d’intermittence du piégeage de la mousse. Cette étude constitue une étape importante de la caractérisation multi-échelle de l’écoulement des mousses en milieux poreux 3D et apporte des éléments de réponse à certaines hypothèses admises.