Hydrogeological Investigations in Deep Wells at the Meuse/Haute Marne Underground Research Laboratory (original) (raw)
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Physics and Chemistry of the Earth, Parts A/B/C, 2011
Within its scientific program devoted to the feasibility of a high level radioactive waste facility in the Callovo-Oxfordian argillaceous rock (COx) of the eastern Paris Basin, Andra has conducted an extensive characterization of the Oxfordian and Dogger limestone formations above and below the COx. More than 25 wells were dedicated to the hydrogeological and geochemical characterization of the Oxfordian and Dogger limestones over a 400 km 2 sector. An original strategy was developed to obtain field hydrogeological measurements and representative formation water samples in these wells. An extensive 3D set of field data and water compositions were obtained over 15 years. The geochemical and isotopic data indicate a meteoric origin for the Oxfordian and Dogger limestone waters. The geological observations revealed a clay rich level horizontally dividing the Oxfordian limestones into two parts in the NE zone of the study area. In the lower Oxfordian, water inflows come mainly from the outcrop in the southeastern part of the study area. Three meteoric water inflows were identified in the upper Oxfordian in the study area: the first one covers the eastern and southeastern part of the area, the second one covers the diffuse fracturation zone (DFZ) south of the area, and the third one is located in the north eastern part of the area. The two first inflows consist of fresh water, while the last one consists of Mg 2+ ,SO 2À 4 and Na + rich waters coming from the erosion of the Purbeckian lithological type facies. Fresh waters from the outcrops flow slowly towards the North West. They equilibrate with the limestone dolomite formations and are enriched by a Na + and Cl À diffusive flux coming from the Dogger through the Callovo-Oxfordian argillaceous rock. These waters mix with the water coming from the North East upper Oxfordian. The Dogger limestone is characterized by sodium chloride groundwaters with higher salinity values than the Oxfordian limestone. North-northwest flows in the Dogger limestone are slower than flows in the Oxfordian formation. In both formations, the DFZ must be considered to be an apart hydrological system.
Physics and Chemistry of the Earth, Parts A/B/C, 2007
Andra, the French National Radioactive Waste Management Agency, is constructing an underground test facility to study the feasibility of a radioactive waste disposal in the Jurassic-age Callovo-Oxfordian argillites. This paper describes the processes, the methods and results of a scientific characterization program carried out from the surface via deep boreholes with the aim to build a research facility for radioactive waste disposal. In particular this paper shows the evolution of the drilling programs and the borehole set up due to the refinement of the scientific objectives from 1994 to 2004. The pre-investigation phase on the Meuse/Haute-Marne site started in 1994. It consisted in drilling seven scientific boreholes. This phase, completed in 1996, led to the first regional geological cross-section showing the main geometrical characteristics of the host rock.
Hydrogeology Journal, 2001
In the context of a research and development program on waste disposal, an experimental site (Tournemire tunnel, Aveyron, France) was selected by the French Institute for Nuclear Protection and Safety (IPSN) in order to undertake studies on potential fluid flow at different scales of space and time within a 250-m-thick argillaceous formation. The argillite has a low natural water content (~3-5%) and very low radii access porosity. Diffusion (tritiated water) coefficients (1×10-12 to 2×10-11 m 2 /s) and hydraulic conductivities derived from different types of laboratory tests (10-14 to 10-13 m/s) are characteristics of a very low-permeable rock. In situ hydraulic tests (including long-term hydraulic-head measurements) were used to obtain values for hydraulic head and hydraulic conductivity at a scale of 1-10 m (10-13 to 10-11 m/s). Despite uncertainties on these data (due to a scale factor, presence of fissures, and possible artefacts due to hydro-chemo-mechanical coupling), it is expected that fluid flow is essentially governed by diffusion processes. Identification of possible natural flows at larger scales of time and space was investigated using natural isotopic tracers from interstitial fluids. Modelling, based on the deuterium profile along the clay formation and assuming pure diffusion processes, provides estimations of possible flow times. However, lack of knowledge concerning the past geological evolution of the site and the possible role of a fracture network do not permit reduction of uncertainties on these estimations at this stage.
Mémoires de la Société …, 2007
The texture and porosity of Callovo-Oxfordian argillites, coming from the Meuse/Haute-Marne region, have been studied at different scales using borehole and laboratory measurements to more spot-like qualitative and quantitative analyses and descriptions of minerals and of the porous space. Due to their limitations and to their resolution, each of the experimental methods used explores differently and often complementarily the porous environment of argillites. The texture is characterised by two-dimensional imaging techniques (optical microscopy, scanning electron microscopy and autoradiography) that provide a view of the material from 0.1 micrometres to a few millimetres or even centimetres. Since borehole measurements are more integrative and representative of the rock in its natural state, they were used to analyse the spatial variability of the porosity. The measurements taken on laboratory samples served to characterise more finely the porous network by providing relevant geometric parameters in order to improve the understanding of the transfer and reaction processes occurring at the interface between fluids and minerals. In the end, a conceptual model for the spatial organisation of the porosity and of the minerals was developed for argillites on the basis of the overall information collected at each step. The reference values for the connected porosity of argillites are obtained by combining the mercury porosity and the calculated porosity in the domain still free from mercury as determined by gas-adsorption techniques. The total connected porosity then varies between 14% for carbonated levels and 19.5% for more argillaceous levels. Those values match those measured in boreholes. In percentage of the total porosity, the macroporosity characterised by mercury porosimetry ranges from 20 to 40%, whereas the mesoporosity resulting from the coupling of mercury porosimetry with nitrogen adsorption oscillates between 60 and 80%. The microporosity determined by nitrogen adsorption is lower than 2%. The relationship between the structure of the porosity and the mineralogy is described by considering 1) the prevailing calcic pole in the upper part of the series around the facies containing argillaceous-limestone beds (lithofacies C2d and C2c, and base of C2b) and 2) the argillaceous pole (lithofacies C2b and C2a). The properties of the porous network are discussed afterwards by reviewing water-saturation effects. Assemblage minéralogique, texture et porosité des argilites du Callovo-Oxfordien de Meuse/Haute-Marne (est du bassin de Paris) Mots-clés.-Injection de mercure, Adsorption d'azote, Minéralogie, Texture, Porosité, Argilites Résumé.-La texture et la porosité des argilites du Callovo-Oxfordien de Meuse/Haute-Marne ont été étudiées à différentes échelles depuis les mesures en forage et en laboratoire jusqu'aux analyses et descriptions plus ponctuelles qualitatives et quantitatives des minéraux et de l'espace poreux. De par leurs limitations et résolution, chaque méthode expérimentale utilisée explore de manière différente et souvent complémentaire le milieu poreux des argilites. La texture a été caractérisée à partir de techniques d'imagerie bidimensionnelles (microscopie optique, microscopie électronique à balayage, autoradiographie), qui apportent une vision du matériau de quelques 0,1 µm à quelques millimètres voir centimètres. Les mesures en forage, plus intégratives et plus représentatives de la roche dans son état naturel, ont permis d'analyser la variabilité spatiale de la porosité. Les mesures conduites sur échantillons en laboratoire ont permis de caractériser plus finement l'espace poreux en fournissant des paramètres géométriques pertinents pour la compréhension des processus de transfert et de réaction à l'interface entre les fluides et les minéraux. In fine, un modèle conceptuel d'organisation spatiale de la porosité et des minéraux a été développé pour les argilites, en cohérence avec la totalité des informations recueillies à chaque étape. Les valeurs de référence de la porosité connectée des argilites sont obtenues en combinant la porosité mercure et la porosité calculée dans le domaine non envahi par le mercure, déterminée par des techniques d'adsorption de gaz. Ainsi, la porosité totale connectée varie entre 14% pour les niveaux carbonatés et 19,5% pour les niveaux les plus argileux. Ces valeurs concordent avec celles mesurées en forage. En pourcentage de la porosité totale, la macroporosité, caractérisée par porosimétrie au mercure, est comprise entre 20 et 40%, la mésoporosité, obtenue en couplant porosimétrie au mercure et adsorption d'azote, est comprise entre 60 et 80% de la porosité alors que la microporosité obtenue uniquement via l'adsorption d'azote est inférieure à 2%. Le lien entre
Physics and Chemistry of The Earth, 2004
Terri (Suisse) : données et interprétation -La migration de gaz dans les roches argileuses est un sujet d'intérêt dans le cadre de différents types d'exploitation du sous-sol : que ce soit par exemple dans le domaine du stockage de gaz naturel, de la séquestration du CO 2 , comme éponte imperméable d'un aquifère, ou dans le domaine du stockage de déchets. Une analyse quantitative de la migration de gaz dans ces milieux à très faible perméabilité nécessite l'estimation des propriétés physiques de l'écoulement. Au laboratoire souterrain du Mont Terri (Suisse), dans les argiles à Opalinus, une roche sédimentaire jurassique, une série de tests hydrauliques et d'injection de gaz a été conduite en forages d'expérimentation. Leur but était en particulier de déterminer les propriétés de transfert des gaz dans cette roche. Cet article présente les résultats d'une campagne de tests (sollicitations de type essai hydraulique classique et test d'injection de gaz et récupération de pression de longue durée), conduite dans la roche « intacte », c'est-à-dire non perturbée mécaniquement par le creusement des galeries. Il présente une interprétation détaillée des tests reposant sur l'ajustement des données expérimentales au moyen d'un logiciel de simulation numérique biphasique (eau/gaz) de l'écoulement en milieu poreux (TOUGH2/iTOUGH2). Par analyse séquentielle, il a été possible d'obtenir un set de paramètres hydrauliques mono-et diphasiques cohérent sur l'ensemble de l'expérimentation. L'utilisation d'informations additionnelles et indépendantes sur les caractéristiques pétrophysiques de la roche (porosité et pression capillaire) a permis de mieux contraindre le problème inverse à l'étude. Bien qu'il soit difficile sur la base des différents modèles et ajustements réalisés, d'obtenir une solution unique en terme de courbe de pression capillaire et de perméabilité relative, les résultats indiquent qu'une paramétrisation classique de type Van Genuchten -Mualem serait valide. Enfin, des simulations prospectives sont présentées qui montrent que l'amélioration de la performance des essais en termes de détermination des paramètres biphasiques nécessiterait une augmentation notable de la durée de l'essai (> 1 an).
Applied Geochemistry, 2008
Diffusive parameters of tritiated water (HTO) and several anionic tracers ( 36 Cl À , 125 I À , 35 SO 2À 4 and 75 SeO 2À 3 ) were determined in the Callovo-Oxfordian argillite formation (Meuse/Haute-Marne, France), and also in the Oxfordian limestone formation, located just above. Twenty two drillcore samples, from depths of 150-480 m and from almost each lithofacies along the same borehole EST205, were tested. Three distinct and complementary experimental set-ups were used (batch, column filled with crushed argillite and through-diffusion experiments) associated with a thorough characterisation of the rock, care being taken to maintain redox conditions. Tritiated water behaviour is similar to water which diffuses in the total porosity of the rock. Tritiated water and anionic tracers displayed analogous diffusive behaviour in calcareous samples with e a (anion)/e a (HTO) = 1 and D e (anion)/D e (HTO) close to 0.85, i.e. the ratio of their diffusion coefficients in free water. Lower and scattered values were observed in the lower part of the Oxfordian limestones which is characterized by the presence of mineralogical heterogeneities and dolomitic diagenesis. In the Callovo-Oxfordian argillite formation, diffusive fluxes of 36 Cl À , 125 I À and 35 SO 2À 4 are similar but lower than that of HTO. The diffusive behaviour analogy between I À and Cl À was verified, as D e (halide)/D e (HTO) and e a (halide)/e a (HTO) ratios were always lower than 1. This reduction in diffusivity is a consequence of the anionic exclusion, which limits the diffusion-accessible porosity to a value lower than the total porosity for anions. A weak sorption of I À and SO 2À 4 on argillite samples was always observed whatever the technique used. In the case of I À , this sorption appears to be partly reversible and kinetically controlled. Very low values of diffusive parameters were obtained for 75 SeO 2À 3 and are still not well explained. Last, diffusive parameters of each radioactive tracer tested can be plotted according to Archie's law, which therefore allows an estimation of D e (non-reactive species) from the knowledge of both the sample total porosity and the corresponding exponent m = 2 for argillite samples.
Physics and Chemistry of the Earth, Parts A/B/C, 2011
In order to assess the feasibility for long lived radioactive wastes storage facilities in deep geological formation, solute transport processes must be investigated in the vicinity of the host formation. In France, the Oxfordian and Dogger limestone layers surrounding the Callovo-Oxfordian (CO x ) argillite in the east of the Paris Basin are investigated for this purpose. More than 60 samples of Oxfordian and Dogger formation groundwater and one sample of Triassic formation groundwater, located at the bottom section of the investigated sedimentary cover, were collected over a 250 km 2 area, and were analyzed for major ions, d 18 O and d 2 H of water, 87 Sr/ 86 Sr, and d 34 S and d 18 O of dissolved sulphate. Oxfordian and Dogger formation water is from meteoric origin, and no direct water flow between Oxfordian, Dogger, nor Triassic formations was evidenced. Mineralization processes of the Dogger limestone groundwater were fully investigated. These processes correspond to a series of geochemical reactions including: calcite dissolution, incongruent dissolution of dolomite, ion addition from upward vertical diffusion through the sedimentary pile inducing cation exchange and further dissolution due to the increased ionic strength of the solutions. A PHREEQC model was developed to simulate inferred chemical processes. The model output is consistent with observed data.