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International audience; An important aspect in CO2 storage in geological media is the quality requirements put on the gases to be stored in terms of risk management. This study investigates and compares, through reactive transport modelling, the potential short-term (5y) reactivity of CO2 gas streams ˗ pure or containing ancillary gaseous compounds (SO2 : 0˗1.5% Wt) ˗ with the reservoir-rock of a limestone aquifer at 75°C. The modelling approach simulates the co-injection of CO2-(SO2) gases, through injection of CO2 (under supercritical form) and simultaneous injection of a SO2 (as a dissolved species solution) rich brine with TOUGHREACT [1]. The numerical simulation results indicate the development of an acidification front (pH < 5) following the progression of the gas migration in the reservoir. After an injection period of 5 years, the acidified zone extends up to 500 m from the injection well, independently of the impurity percentage of the CO2 gas stream. In close proximity of the injection well (0-10m), substantial calcite dissolution, together with albite and K-feldspar dissolution, result in a drastic increase of the permeability (1 order of magnitude) and porosity (x2). When CO2 is injected alone, anhydrite also precipitates in this reservoir zone. Significant calcite dissolution is also predicted in the zone 50-100m ˗ a highly reactive zone˗ resulting in a local permeability and porosity increase. Because of its high solubility, SO2 mainly remains in the brine (SO2 content lower in the CO2-rich phase than in the injected gas stream), decreasing its pH/Eh (relatively to pure CO2). Dissolved SO2 is lowly reactive with reservoir minerals.

National audience; Ce numéro est issu des échanges qui se sont tenus lors du colloque organisé par la SFER en février 2015 à Rennes et consacré à l’évolution des structures d’exploitation et des formes d’exercice de l’activité agricole. A l’heure où des changements structurels importants continuent de s’opérer au sein de l’agriculture française, il a semblé utile de prendre le temps de la réflexion pour analyser les tendances...(...)

International audience

La théorie leibnizienne de l'expression, centrée sur la notion de relation, introduit, entre les mots des langues naturelles et la pensée, un rapport qui n'est pas seulement de représentation. Elle introduit également une parenté entre langues naturelles et langages formels. L'objectif de l'article est de mener une confrontation entre l'analyse par Leibniz des relations dans les langues naturelles et dans les langages symboliques afin de mettre en évidence leurs analogies. L'article cherchera à montrer : l'existence d'une double articulation dans les langues naturelles et les langages formels tels que les conçoit Leibniz ; le caractère mathématique de son analyse des prépositions ; l'arrière-plan logique de son analyse des dérivations sémantiques. Leibniz's theory of universal expression focuses on the notion of relationship and introduces a link between the words of a natural language and the mind which is not only that of representation. It also establishes similarities between natural languages and formal languages. The aim of our paper is to compare Leibniz’s analysis of the relations one can establish in natural languages and in symbolic languages, to highlight their similarities. The article seeks to demonstrate the existence of a double articulation both in natural languages and in formal languages such as Leibniz conceived them; the mathematical nature of his analysis of prepositions, the logical background of his analysis of semantic derivations.

International audience; Groundwaters in parts of the Paris Basin (France) are facing increasing selenium (Se) contents that can exceed the drinking water limit of 10 µg/L according to the European Framework Directive in the field of water policy (2000/60/EC). To better understand the groundwater origins and the selenium dynamics, the water chemistry of the Chalk aquifer supplying drinkable water to Lille city was studied. This area is submitted to quantitative and qualitative pressure from industrial, urban and agriculture origins. An integrated study was settled to determine the water sources and dynamics of elements, with a focus on Se. After a large chemical characterisation of the groundwater chemistry in the four field wells, a monthly monitoring was held in four wells and in the Deûle channel. Chemical analysis of major and trace elements, stable isotopes (δ18O, δ2H), strontium isotopes, and δ34S and δ18O of sulphates were realised. The chemical composition of solids sampled at various depths at vicinity of the four wells was also analysed. The specific geochemical signature of groundwater as revealed by Sr isotopes, in addition to element concentrations ratios like Mg/Sr and Se/Sr, highlighted mixture of three main groundwaters bodies: (1) the upstream groundwaters in the recharge area with the most radiogenic 87Sr/86Sr isotopic signature; (2) the confined groundwaters with high Sr concentrations due to water-rock interactions and the lowest 87Sr/86Sr isotopic signature close to the one of the chalk in Paris and London basins; (3) the Se-rich formations of Tertiary and Quaternary. The contents of Se, mainly present as SeVI (and locally as SeIV), displayed spatial and temporal disparities that can be explained by geological and hydrogeological conditions. Se-rich clayed sediments originating from the dismantling of Se-rich tertiary formations (i.e. Ypresian) overlay the chalk formation and can be found in saturated conditions depending of the water table level. Oxidation of Se0, Se-pyrite and Se linked to organic matters happens according to two pathways. The first one is oxidation of Se species present in the reductive clayed sediments by oxidizing groundwaters during periods of high piezometric levels. The decrease of the piezometric level induces a decrease of the Se contents in groundwaters. Negative δ34S (0 to -28 ‰) coherent with pyrite oxidation are observed in groundwater. The second one is linked to the infiltration of nitrate-rich recharge waters through quaternary loess which also contain Se. In this case, δ34S of groundwaters are slightly positive and close to the signature of fertilizers. Denitrification by pyrite or Se0 oxidation plays a great role in enhancing Se mobility in a very reactive system. To limit the Se content in groundwaters, a precise water management is needed, e.g. mainly maintaining low piezometric levels in the chalk aquifer or avoiding mixings between contaminated wells, together with a precise knowledge of the geology of the quaternary clayed sediments.

International audience

International audience

Wells drilled through low-permeable caprock are potential connections between the CO2 storage reservoir and overlying sensitive targets like aquifers and targets located at the surface. The long term well sealing integrity is therefore essential for the fluids confinements. In this work, we propose to develop an integrated framework constituted by field experiment, laboratory characterization and modeling in order to get better insights into the conditions of a good well sealing integrity on the long term scale. Our work is carried out within the context of the EU-FP7 project UltimateCO2 (Understanding the Long Term fate of geologically stored CO2) led by BRGM and dedicated to the long term fate of CO2 focusing on several physical processes. A field experiment is thus being currently set-up in the underground rock laboratory of Mont-Terri (St Ursanne, canton of Jura, Switzerland).

International audience

In mine tailings sites, where sulfide minerals are in contact with atmospheric humidity and meteoritic water, oxidation of sulfides generate acidity leading to mobilization of metals and metalloids through the soil to surface and underground waters. The resulting acid mine drainage can impair dramatic environmental problems (i.e., toxicity of arsenic III, etc.). In the old gold mine of Chéni (France), large physical, chemical and microbiological datasets are available: mineralogical compositions of the tailings [1], long-term survey of drainage waters chemistry [2] and microbiological characterizations [3]. The pH/Eh of sampled waters through the tailing column (unsaturated and saturated zones) is in the range of 2.9-7.6 and 0-700mV respectively. Analysis of these data permitted to identify the key processes of mine water behavior. Numerical simulations, using the geochemical software PHREEQC [4], were performed aiming to identify the key mechanisms and understand those coupling processes. First analysis of geochemistry show different redox potentials for each element (Fe, As, O2, N, S). Such redox disequilibrium, known in natural waters [5] is rarely take into account in modeling. In our work, redox decoupling of the thermodynamical database is used to model redox behavior of mine water. Biological oxidation of arsenic was identified as an active and sustained process in such systems. Experimental results of biological As oxidation was used to develop a thermokinetic model coupling geochemistry and biologic activity [6] and reproducing the pH-dependant activity of bacterial population. Finally, we elaborate a mixed biogeochemical model to reproduce the behavior of an acid mine drainage, which takes into account major processes including bacterial activities, precipitation of Fe-containing minerals (Schwertmannite, ferrihydrite, jarosite) and surface complexation. [1] Roussel (1998) PhD thesis, Univ. Limoges [2] Bodénan et al. (2004) Appl. Geochem. 19 pp. 1785-1800 [3] Battgalia (2002) J. Appl. Micr. 93 pp. 656-667 [4] Parkhurst et Appelo (1999) USGS Rep. 99-4529 [5] Lindberg and Runnels (1984) Science 225 pp. 925-927 [6] Jin and Bethke (2005) Geoch. Cosm. Acta 69 pp. 1133-1143

International audience

In the context of the reduction of greenhouse gas emissions, capture processes of CO2 constitute the main problem to solve. Indeed this step has the most important cost of all the treatment chain: capture/transport/sequestration. As a function of the industrial sources (energy production, iron industry, concrete production, etc.) and capture process, the composition of the gaseous mixture should vary considerably in nature and concentration. The degree of purity of captured CO2 is thus a key factor for transportation, injection and sequestration. In addition to CO2 and water, more or less important quantities of other gases (O2, N2, SOx, NOx, H2, CO, Ar...) would be admixed in different proportions. These gases are taken into account in industrial processes of capture but they remain poorly studied for the development of geological storage technologies. Furthermore, co-injected gases could mix with pre-existing natural gases (CH4, gas condensates, H2S) in depleted hydrocarbon reservoirs. Gas mixing could induce mineral dissolution – precipitation reactions and/or modifications of pressure - temperature properties of the system. The impact of such co-injected and/or residual gases on the mineral assemblages from reservoir, cap-rock and well-bore completion has to be understood under geological storage conditions at high pressures, high temperatures, and high salinity. In this context, a project called "Gaz Annexes" supported by the french national agency for research (ANR) was conducted since 2006 with some of the major actors working on the CCS in France, i.e. Nancy University and ENSIC, BRGM, IFP, Ecole des Mines de Paris and Total. The goal of the project “Gaz Annexes” is to acquire new data to characterize phase equilibria of geological systems including co-injected gases such as SOx, NOx, N2, Ar in order to improve our understanding of the reactivity of such systems. Hence, new thermodynamic data relevant for CO2 injection-storage conditions were measured and fitted to extract the lacking Equation Of State (EOS) parameters. The project is divided in five phases: i) Qualitative and quantitative compilation of co-injected gases generated as a function of industrial and capture processes. The goal is to determine which are the reactive gases and which quantity could be injected, ii) Acquisition of new experimental data on water/gas/salt systems by performing lab experiments and in situ measurements. Data are collected using two main analytical methods: chromatography and Raman spectroscopy, iii) Thermodynamic characterization of equilibrium between the different fluid phases (gas mixtures and saline waters), iv) Integration of the relevant new data into hydro-geochemical codes in order to better predict the behaviour of CO2 and co-injected gases into saline aquifers or oil reservoirs, v) Validation and application of developed geochemical codes on experimental data obtained on rock/water/gas systems with laboratory experiments carried out under geological conditions of storage. The chemical behaviour of co-injected (i.e., SOx, NOx, ...) gases if of prime interest if considering that such gases could generate very high acidity of the native brines and could accelerate the water – rock interactions. This could lead to an important impact on the petrophysical properties (porosity, permeability, etc.) of the whole reservoir. The region close to well bore of CO2 injection could be also drastically affected causing possible difficulties for the injectivity process. The obtained results will be presented for discussion at the GHG10 congress.

International audience; Discounting the future, i. e., depreciating the value of future properties соmpаrеd to present ones, represents the main cause of false judgments in ethics for John Locke and Leibniz. This article aima to analyse Locke's attempts to outline the mechanіsm of discounting the future in his Essay Concerning Нuman Understanding and Leibniz' efforts to give the phenomenon a mathematical formalization. Locke and Leibniz disagree about its causes and offer different standards of virtue in objecting to i[. According to Locke, virtue aims to do away with all forms of discounting while Leibniz argues that the phenomenon can be rationalised using the techniques for cultivating moral virtue as a means of anticipation.

Il faut lire les "Nouveaux Essais sur l'entendement humain" de Leibniz à la fois comme un grand livre de philosophie et comme une grande œuvre littéraire. Ils ne se résument pas à une confrontation figée entre les grandes thèses de l'"Essai sur l'entendement humain" de Locke et les grands principes de la philosophie leibnizienne. Ce qui sépare les deux philosophes n'est pas une série de réponses à apporter aux mêmes questions, mais un ensemble de différends sur la manière de poser les questions. Dès lors, le débat philosophique exige un dispositif rhétorique surmontant la disparité des réseaux conceptuels et des langages philosophiques. Le dispositif choisi par Leibniz est une intrigue au cours de laquelle un personnage est conduit comme malgré lui d'une conviction philosophique à une autre. Philalèthe adresse à son interlocuteur non pas un copier-coller des propositions de Locke mais leur réécriture riche des écarts nécessaires à son aventure philosophique personnelle.

International audience

The geochemistry of natural system as old mine site is influenced by biological activity. Only informatics tools taking into account geochemistry, hydrodynamics and microbiology will be able to analyse, and then predict, this complex system evolution. For about ten years numerical tools, as CHESS and HYTEC, are able to take into account most of the geochemical and hydrodynamical processes present in soil. The goal of this work is to extend this tools to the microbiologic activity. CHESS calculate the geochemical equilibrium speciation using a modified Newton-Raphson process. The same method is extended to the calculation of reactions mechanisms containing biological kinetics. Most of the biological kinetic laws can now be used: Monod law, inhibition law and thermodynamical law. Moreover others options of this tools, like coupling with transport process (HYTEC), are maintained. The implementation of this code is first verified by the modelling of several cases from literature. The code is then used for the calculation of experimental study realized at the BRGM, involving a bacterial consortium responsible of a reductive dissolution of an hydrous ferric oxyde (HFO) enriched by arsenic. The non congruent mobilisation of Fe and As is explained by sorption on HFO and activity of two bacterial metabolism which degrades organic matter and reduced Fe and As. The old site mine of Carnoules (Gard, French) is studied. The experiments, realized at the university of Montpellier, permitted to study the natural biogeochemical evolution of acid mine drainage. The calculation take into account the biologic aerobic oxidation of Fe and As and the precipitation of amorphous Fe-As gel. The kinetic and thermodynamic parameter are the used on a modelling at the field scale. These applications prove the interest of the computational tools in understanding water-mineral interface, in which precipitation-dissolution can be controlled by bacterial population. Moreover, CHESS and HYTEC extension permitted to considerably extend the fields of applications., La géochimie est souvent influencée par l'activité biologique. Des logiciels tels que CHESS et HYTEC modélisent la plupart des processus géochimiques et hydrodynamiques et permettent d'analyser, puis de prédire, l'évolution de systèmes complexes comme les anciens sites miniers. L'objectif est d'étendre ces outils à la prise en compte de l'activité bactérienne. Dans CHESS, la méthode de Newton-Raphson, qui calcule la spéciation géochimique à l'équilibre, a été étendue à la modélisation de systèmes réactionnels composés de cinétiques biologiques (lois de Monod, d'inhibition, thermodynamique). Les autres options de cet outil comme le couplage avec le module de transport (HYTEC) ont été maintenues. L'implémentation du code a été vérifiée par la modélisation de quelques cas tirés de la littérature. L'outil a ensuite été utilisé pour la modélisation d'expériences de dissolution réductives biologiques d'hydroxydes de fer (HFO) riches en As, réalisées au BRGM. La mobilisation non congruente de Fe et As est expliquée par la sorption sur l'HFO et par les réductions biologiques de Fe et As. L'ancien site minier de Carnoulès (Gard, France) a été étudié lors d'expériences, réalisées à l'université de Montpellier, qui retracent l'évolution géochimique de l'eau acide de drainage minier. Leur modélisation prend en compte les oxydations aérobies biologiques de Fe et As et la précipitation d'une phase amorphe de FeIII et d'AsV. Les expériences ont permis de fixer les paramètres thermodynamiques et cinétiques utilisés pour la modélisation à l'échelle du terrain. Au delà de l'étude de l'interface eau-minéral, l'extension des outils CHESS et HYTEC va permettre d'étendre considérablement le champs de leurs applications.

The geochemistry of natural system as old mine site is influenced by biological activity. Only informatics tools taking into account geochemistry, hydrodynamics and microbiology will be able to analyse, and then predict, this complex system evolution. For about ten years numerical tools, as CHESS and HYTEC, are able to take into account most of the geochemical and hydrodynamical processes present in soil. The goal of this work is to extend this tools to the microbiologic activity. CHESS calculate the geochemical equilibrium speciation using a modified Newton-Raphson process. The same method is extended to the calculation of reactions mechanisms containing biological kinetics. Most of the biological kinetic laws can now be used: Monod law, inhibition law and thermodynamical law. Moreover others options of this tools, like coupling with transport process (HYTEC), are maintained. The implementation of this code is first verified by the modelling of several cases from literature. The code is then used for the calculation of experimental study realized at the BRGM, involving a bacterial consortium responsible of a reductive dissolution of an hydrous ferric oxyde (HFO) enriched by arsenic. The non congruent mobilisation of Fe and As is explained by sorption on HFO and activity of two bacterial metabolism which degrades organic matter and reduced Fe and As. The old site mine of Carnoules (Gard, French) is studied. The experiments, realized at the university of Montpellier, permitted to study the natural biogeochemical evolution of acid mine drainage. The calculation take into account the biologic aerobic oxidation of Fe and As and the precipitation of amorphous Fe-As gel. The kinetic and thermodynamic parameter are the used on a modelling at the field scale. These applications prove the interest of the computational tools in understanding water-mineral interface, in which precipitation-dissolution can be controlled by bacterial population. Moreover, CHESS and HYTEC extension permitted to considerably extend the fields of applications., La géochimie est souvent influencée par l'activité biologique. Des logiciels tels que CHESS et HYTEC modélisent la plupart des processus géochimiques et hydrodynamiques et permettent d'analyser, puis de prédire, l'évolution de systèmes complexes comme les anciens sites miniers. L'objectif est d'étendre ces outils à la prise en compte de l'activité bactérienne. Dans CHESS, la méthode de Newton-Raphson, qui calcule la spéciation géochimique à l'équilibre, a été étendue à la modélisation de systèmes réactionnels composés de cinétiques biologiques (lois de Monod, d'inhibition, thermodynamique). Les autres options de cet outil comme le couplage avec le module de transport (HYTEC) ont été maintenues. L'implémentation du code a été vérifiée par la modélisation de quelques cas tirés de la littérature. L'outil a ensuite été utilisé pour la modélisation d'expériences de dissolution réductives biologiques d'hydroxydes de fer (HFO) riches en As, réalisées au BRGM. La mobilisation non congruente de Fe et As est expliquée par la sorption sur l'HFO et par les réductions biologiques de Fe et As. L'ancien site minier de Carnoulès (Gard, France) a été étudié lors d'expériences, réalisées à l'université de Montpellier, qui retracent l'évolution géochimique de l'eau acide de drainage minier. Leur modélisation prend en compte les oxydations aérobies biologiques de Fe et As et la précipitation d'une phase amorphe de FeIII et d'AsV. Les expériences ont permis de fixer les paramètres thermodynamiques et cinétiques utilisés pour la modélisation à l'échelle du terrain. Au delà de l'étude de l'interface eau-minéral, l'extension des outils CHESS et HYTEC va permettre d'étendre considérablement le champs de leurs applications.

International audience

International audience

International audience

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International audience

International audience

International audience

International audience

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International audience

International audience