Étude des transferts hydriques en milieu poreux en présence de polymères rétenteurs d'eau : application au mortier

In building materials, such as mortars, cellulose ethers (CE) are used as water-retention agents. They prevent the loss of water due to absorption into the substrate during curing stage. They maintain wet conditions for proper hardening and final properties. However, the cause of retention remains unknown. First, we show through filtration tests and usual characterization methods (microscopy, light scattering) that CE solutions are composed of polydisperse aggregates of several tens of microns in diameter. We then show that a CE solution passing through a model porous medium (sieve) progressively block the sieve, even if the mesh size is much larger than the aggregates diameter, due to a statistical effect of blocking. This jamming effect also occurs during the flow through a 3D porous medium (stacks of glass beads), which led to the stopping of the fluid after a certain penetration depth of the medium. Finally, coming back to the retention standard tests with the real material (mortar) and comparing them to the filtration test we show that the latter is a good alternative test to characterize the CE retention capacityLes éthers de cellulose (EC) sont des agents rétenteurs d'eau très utilisés dans les matériaux de construction: ils limitent fortement la perte d'eau due principalement à l'absorption dans le substrat pendant la cure, favorisant ainsi les réactions d'hydratation du ciment nécessaires à la prise qui assurent de bonnes propriétés mécaniques pour le matériau final. Cependant les causes exactes de ce phénomène de rétention d'eau restent encore incomprises à ce jour. Dans ce travail de thèse, afin d'analyser les mécanismes de la rétention, nous tentons de mieux comprendre pourquoi et comment les transferts hydriques sont modifiés en présence d'EC. Dans un premier temps, nous montrons, grâce à des tests de filtration et par les méthodes usuelles de caractérisation (microscopie, diffusion de la lumière) que les EC en solution forment des agrégats polydisperses de plusieurs dizaines de microns de diamètre. Nous montrons ensuite qu'une solution d'EC passant à travers un matériau poreux modèle (tamis) bouche progressivement ce tamis, même si la taille de maille est nettement supérieure à celle des agrégats, du fait d'un effet de blocage statistique. Cet effet de coincement se produit également lors de l'écoulement à travers un milieu poreux 3D (empilements de billes de verre), ce qui conduit à l'arrêt du fluide après une certaine hauteur de pénétration dans le milieu. Enfin, en revenant aux tests standards de rétention avec le matériau réel (mortier) puis en les comparant au test de filtration à travers un tamis nous montrons que ce dernier est un bon test alternatif qui permet de caractériser la capacité de rétention des E

Study of hydric transfers in porous media with water retaining polymers : application to mortar

Les éthers de cellulose (EC) sont des agents rétenteurs d'eau très utilisés dans les matériaux de construction: ils limitent fortement la perte d'eau due principalement à l'absorption dans le substrat pendant la cure, favorisant ainsi les réactions d'hydratation du ciment nécessaires à la prise qui assurent de bonnes propriétés mécaniques pour le matériau final. Cependant les causes exactes de ce phénomène de rétention d'eau restent encore incomprises à ce jour. Dans ce travail de thèse, afin d'analyser les mécanismes de la rétention, nous tentons de mieux comprendre pourquoi et comment les transferts hydriques sont modifiés en présence d'EC. Dans un premier temps, nous montrons, grâce à des tests de filtration et par les méthodes usuelles de caractérisation (microscopie, diffusion de la lumière) que les EC en solution forment des agrégats polydisperses de plusieurs dizaines de microns de diamètre. Nous montrons ensuite qu'une solution d'EC passant à travers un matériau poreux modèle (tamis) bouche progressivement ce tamis, même si la taille de maille est nettement supérieure à celle des agrégats, du fait d'un effet de blocage statistique. Cet effet de coincement se produit également lors de l'écoulement à travers un milieu poreux 3D (empilements de billes de verre), ce qui conduit à l'arrêt du fluide après une certaine hauteur de pénétration dans le milieu. Enfin, en revenant aux tests standards de rétention avec le matériau réel (mortier) puis en les comparant au test de filtration à travers un tamis nous montrons que ce dernier est un bon test alternatif qui permet de caractériser la capacité de rétention des ECIn building materials, such as mortars, cellulose ethers (CE) are used as water-retention agents. They prevent the loss of water due to absorption into the substrate during curing stage. They maintain wet conditions for proper hardening and final properties. However, the cause of retention remains unknown. First, we show through filtration tests and usual characterization methods (microscopy, light scattering) that CE solutions are composed of polydisperse aggregates of several tens of microns in diameter. We then show that a CE solution passing through a model porous medium (sieve) progressively block the sieve, even if the mesh size is much larger than the aggregates diameter, due to a statistical effect of blocking. This jamming effect also occurs during the flow through a 3D porous medium (stacks of glass beads), which led to the stopping of the fluid after a certain penetration depth of the medium. Finally, coming back to the retention standard tests with the real material (mortar) and comparing them to the filtration test we show that the latter is a good alternative test to characterize the CE retention capacit

Study of hydric transfers in porous media with water retaining polymers : application to mortar

Les éthers de cellulose (EC) sont des agents rétenteurs d'eau très utilisés dans les matériaux de construction: ils limitent fortement la perte d'eau due principalement à l'absorption dans le substrat pendant la cure, favorisant ainsi les réactions d'hydratation du ciment nécessaires à la prise qui assurent de bonnes propriétés mécaniques pour le matériau final. Cependant les causes exactes de ce phénomène de rétention d'eau restent encore incomprises à ce jour. Dans ce travail de thèse, afin d'analyser les mécanismes de la rétention, nous tentons de mieux comprendre pourquoi et comment les transferts hydriques sont modifiés en présence d'EC. Dans un premier temps, nous montrons, grâce à des tests de filtration et par les méthodes usuelles de caractérisation (microscopie, diffusion de la lumière) que les EC en solution forment des agrégats polydisperses de plusieurs dizaines de microns de diamètre. Nous montrons ensuite qu'une solution d'EC passant à travers un matériau poreux modèle (tamis) bouche progressivement ce tamis, même si la taille de maille est nettement supérieure à celle des agrégats, du fait d'un effet de blocage statistique. Cet effet de coincement se produit également lors de l'écoulement à travers un milieu poreux 3D (empilements de billes de verre), ce qui conduit à l'arrêt du fluide après une certaine hauteur de pénétration dans le milieu. Enfin, en revenant aux tests standards de rétention avec le matériau réel (mortier) puis en les comparant au test de filtration à travers un tamis nous montrons que ce dernier est un bon test alternatif qui permet de caractériser la capacité de rétention des ECIn building materials, such as mortars, cellulose ethers (CE) are used as water-retention agents. They prevent the loss of water due to absorption into the substrate during curing stage. They maintain wet conditions for proper hardening and final properties. However, the cause of retention remains unknown. First, we show through filtration tests and usual characterization methods (microscopy, light scattering) that CE solutions are composed of polydisperse aggregates of several tens of microns in diameter. We then show that a CE solution passing through a model porous medium (sieve) progressively block the sieve, even if the mesh size is much larger than the aggregates diameter, due to a statistical effect of blocking. This jamming effect also occurs during the flow through a 3D porous medium (stacks of glass beads), which led to the stopping of the fluid after a certain penetration depth of the medium. Finally, coming back to the retention standard tests with the real material (mortar) and comparing them to the filtration test we show that the latter is a good alternative test to characterize the CE retention capacit

Microfluidic approaches for accessing thermophysical properties of fluid systems

Thermophysical properties of fluid systems are highly desirable as they are used in many industrial processes both from a chemical engineering point of view and to push forward the development of modeling approaches. To access these data, microfluidic approaches have recently attracted increasing interest as they provide flexible and reliable ways for measurements, leading to fast screening capabilities compared to conventional experimental systems. In this review, we present a general overview of microfluidic methodologies integrating in situ characterization to determine thermodynamic properties of fluid systems. In addition to drastically reducing the time to reach thermodynamic equilibria, one major advantage of microfluidics is to provide optical access to the fluid behavior, even under harsh conditions. Therefore, several in situ characterization techniques can be implemented to get insights into fluid properties. Here, we emphasize approaches developed using high pressure and high temperature microfluidics. Indeed, such conditions are of interest for energy industries and present plenty of challenges. Several recent examples of high pressure microfluidics optical approaches will be detailed, in particular to determine viscosity and density, phase equilibria, mass transfer coefficients and solubility parameters.Microfluidic Approaches mimicking BIoGeological conditions to investigate subsurface CO2 recyclin

Transport of EOR polymer solutions in low permeability porous media: impact of clay type and injection water composition

International audienceThe application of polymer flooding for enhanced oil recovery (EOR) to low-permeability porous media (below 100mD) can be very challenging as high polymer retention and poor injectivity are frequently observed. The challenges are mostly related to polymer solutions properties (ionic strength and hardness) and porous media mineralogy (clay content). This paper reports on an experimental study that aims at drawing a better picture of the mechanisms governing the transport of polymer solutions in low permeability clayey porous media. Results confirm the major role played by the injection water composition (salinity and hardness) on polymer conformation and on polymer-minerals interactions. Strong interactions between polymer and clay are also evidenced with significant differences according to the clay type: good propagation and high polymer retention in an uncharged and non-swelling clay (kaolinite) and poor propagation with lower than expected retention in charged or swelling clays (illite, smectite). For kaolinite, the results are interpreted in terms of fast formation of a polymer adsorbed layer on the solids surface whereas, for illite and smectite, they can be explained by the slow diffusion of polymer into clay aggregates, whose presence was evidenced by microscopic analysis. These outcomes stand as new elements for understanding and modeling the transport of polymer solutions in low permeability sandstone reservoirs. They also allow classifying the clays in view of their practical impact on the feasibility of polymer flooding operations

Transport of HPAM Solutions in low Permeability Porous Media: Impacts of Salinity and Clay Content

International audienceChemical EOR is now considered as an attractive option for low permeability reservoirs, in particular wherelack of gas supply does not allow gas injection processes. However, its application can be challenging forpermeabilities below 100 mD, as poor injectivity and high chemical retention are frequently observed inthese cases. This work aimed at investigating the impact of both chemical and mineralogical parameters onthe transport of polymer solutions in well-controlled low permeability porous media.The intrinsic viscosity and hydrodynamic size of partially hydrolyzed polyacrylamide (HPAM)solubilized in brines of variable ionic strengths and hardnesses were firstly investigated. Polymer injectioncorefloods were then conducted using granular packs (sand and clays mixtures) with similar petrophysicalcharacteristics (permeability 60-80 mD) but having several controlled mineralogical compositions. Thegranular packs were especially characterized in terms of structure (SEM) and specific surface area (BET)before and after polymer injections. The main observables from the coreflood tests were the resistanceand residual resistance factors generated by the polymer, the polymer inaccessible pore volume and itsirreversible retention.Homogenous and reproducible granular packs were successfully prepared thanks to a dedicatedmethodology and using different ratios of quartz and clays (kaolinite and illite separately).Results from the viscometric analysis showed that the intrinsic viscosity of the HPAM solutions decreasedwith increasing total salinity, as expected from charge screening, and that it decreased sharply in presenceof divalent cations, even at low ionic strength, which was less expected.Coreflood experiments showed that polymer retentions, resistance factors and irreversible resistancefactors increased significantly:– with increasing ionic strength and hardness for porous media of a given mineralogicalcomposition. This appeared consistent with the outcomes of the viscometric study andconfirmed the major impact of hardness;– in presence of kaolinite and illite, even at low ionic strength and hardness.The polymer inaccessible pore volume was significantly impacted by the presence of clays, but not bythe ionic strength and hardness. Analysis of the results indicated that these effects could not be attributedonly to polymer adsorption linked to the increase of specific surface area, but that more complex polymeradsorption/retention mechanisms occur depending on the clay type (layer charge and expandability).This systematic study allows dissociating the impacts of salinity, hardness and clay contents/types on thetransport of polymer solutions in low permeability porous media. The results obtained should be of interestto the chemical EOR industry as they provide guides to help tuning the injection brine composition andpolymer concentration to the reservoir properties

Controlled imbibition in porous medium from a soft wet material (poultice)

International audienceWe provide a first approach of the mechanisms of liquid imbibition in a porous medium from a wet paste in contact with this substrate. Through Magnetic Resonance Imaging (MRI) we first show that, in contrast with intuition, the liquid can invade the substrate even if it has a larger pore size than the paste, which induces a lower capillary pressure in the substrate. This phenomenon happens because the paste can easily shrink. We then show that the imbibition stops when the capillary pressure in the substrate balances the stress needed to further contract the paste. The dynamics of the process then mainly results from the competition of these two effects plus the pressure gradient associated with the liquid flow through the paste. This in particular shows that the liquid penetration in a porous medium, from a poultice in contact with this medium, may be controlled by adjusting the poultice characteristics

Access to Emissions Distributions and Related Ancillary Data through the ECCAD database

During the past few years, the ECCAD (Emissions of atmospheric Compounds & Compilation of Ancillary Data) database was developed in order to provide a user-friendly access to surface emissions and ancillary data, i.e. data on land use, active fires, burned areas, population, etc. This database and the emissions portal of the GEIA (Global Emissions InitiAtive) project have been merged. ECCAD is a sub-project of the ETHER French Atmospheric Chemistry Data Centre (CNES and CNRS, http://www.pole-ether.fr). The ECCAD database includes currently a large diversity of datasets, which provide global and regional surface emissions for a large set of chemical compounds. All the data are provided at a 0.5x0.5 or 1x1 degree resolution. ECCAD provides detailed metadata on each of the datasets, including information on complete references and methodology, and links to the original inventories. Several tools are provided for the visualization of the data, for computing global and regional totals and for an interactive spatial and temporal analysis. The data can be downloaded as interoperable NetCDF CF-compliant files, i.e. the data are compatible with many other client interfaces and can be downloaded through requests as geographical coverage or geo-referenced maps. ECCAD has currently more than 700 users originating from more than 30 countries. ECCAD benefits from this large international community of users to expand the number of emission datasets made available. The ECCAD database and the web interface are in continuous development: new tools are being built to improve the analysis and comparison of emissions and ancillary data. These new tools include a regridding tool, arithmetic expressions to combine different maps, interactive selection of scale values, and new tools for temporal profiles analysis. Comparisons of data at different scales is also in development. An online module to calculate biomass burning emissions is being improved, and will also be extended to anthropogenic emissions. The presentation will provide information on all the datasets available within ECCAD, as well as examples of the analysis work that can be done online from the database. All the datasets, associated metadata, tools and download can be achieved from the ECCAD website: http://eccad.pole-ether.f

Synthesis and Enzymatic Conversion of Amino Acids Equipped with the Silanetriol Functionality: A Prelude to Silicon Biodiversification

Abstract Synthetic routes are reported for the three analogues of the simplest L‐2‐amino‐dicarboxylic acids, aspartate, glutamate, and aminoadipate, in which the silanetriol group (Si(OH)3) replaces the distal carboxyl group (CO2H). Direct access to the silanetriol amino acids relied either on catalytic hydrosilylation of a terminal alkene using triethoxysilane, or on alkylation of a glycine equivalent anion by triallyl(iodomethyl)silane. In both cases, acid hydrolysis afforded the silanetriol amino acids. These were shown to self‐assemble into siloxane Si‐O clusters as their concentration in water increased in the pH range of 1–12. Such reversible cross‐linking did not prevent silanetriol amino acids from serving as substrates of an aminotransferase enzyme, boding well for their utilization as microbial nutrients to encompass silicon in future stages of metabolism and polypeptide edifices