To trap CO2 industrially

Pour diviser par quatre les émissions de CO2 à l'horizon 2050, tous les outils efficaces devront être utilisés. Parmi eux, la capture du CO2 puis son stockage de longue durée dans des formations géologiques appropriées est une option considérée avec un intérêt croissant par de nombreux pays. Les différents défis technologiques économiques attachés à cette filière seront présentés, ainsi que les questions relatives à la sécurité. Les potentiels de stockage, les lieux favorables et les mécanismes qui concourent à la robustesse globale de cette solution seront évoqués

Uncertainties related to sampling and their impact on the chemical analysis of groundwater

International audienceIt is necessary to take into account the impact of the field stages on the chemical analysis of natural water, in terms of both sampling representativeness and spatial and temporal variability. We demonstrated this need in studies conducted at two industrial sites, which involved groundwater contaminated with metals and organochlorine compounds.We developed a methodology for estimating the uncertainties linked to the entire analytical chain — from sampling to handing over results to the client. This methodology is based on the use of groundwater chemical logs acquired in the field for evaluating field heterogeneity and identifying water levels to be sampled.We validated the methodology through specifically-designed repeatability and reproducibility tests carried out in the field. The results illustrated that a geochemical understanding of the natural environment and the changes it undergoes is possible, but requires an international consensus on the methodology best suited to application in field tests. If not, major inconsistencies and/or erroneous interpretations may arise in environmental monitoring programs

Natural flow and vertical heterogeneities in a sedimentary geothermal reservoir (Paris Basin, France): Geochemical investigations

Three geothermal wells tapping the Dogger aquifer were studied in detail for their variations in chemical composition with time or conditions of exploitation. Analytical improvements for the determination of Cl, SO{sub 4}, Ca, Mg, Na and K make it possible to detect variations respectively of 0.15, 0.8, 0.6, 1.8, 1.8 and 1.4 %. Despite the fact that the natural flow may be important in some parts of the basin aquifer, we conclude that this factor is not responsible for the small variations noticed in mineralization within the one year survey period. The results concerning reactive and nonreactive species are best explained if a vertical heterogeneity of the chemistry of the fluid is assumed. A number of calcareous sub-layers, already demonstrated by geological studies, contribute to varying degrees to the production of the hot water. The changes in pumping rates, which are fixed according to external requirements, play a major role in the hydrodynamic and chemical disequilibrium of the wells. The consequences for the geothermal exploitations are emphasized

Dépôts minéraux à l'émergence de sources thermales sulfurées sodiques des Pyrénées Orientales

A study of minerals deposited at the emergence of some Pyrenean hot springs shows the occurrence of two kinds of deposits. A first kind are minerals deposited under equilibrium conditions from elements in solution. A second kind are minerals resulting from wall-rock alteration and formed under non equilibrium conditions relatively to the bulk of the hydrothermal water. These results allow to point out several limitations to the possibility of application of equilibrium data to the interpretation of hydrothermal mineral associations. Our data have allowed a calculation of a new value for the Gibbs free energy of zoïzite : ∆G°₂₉₈(zoïzite) = — 6 507.6 kJ. mole⁻¹.L'étude des minéraux déposés aux émergences de quelques sources thermales des Pyrénées a permis de caractériser deux sortes de dépôts. D'une part, des minéraux formés directement à partir des éléments en solution dans des conditions voisines de l'équilibre. D'autre part, des minéraux formés par une interaction entre l'eau hydrothermale et la roche à l'émergence et se formant hors d'équilibre avec l'eau hydrothermale. Ces résultats permettent d'apporter certaines limitations aux possibilités d'application de notion d'équilibre dans l'interprétation de certaines néoformations hydrothermales. Nos données permettent aussi de calculer une nouvelle valeur pour l'enthalpie libre de formation de la zoïzite, soit ∆G°₂₉₈(zoïzite) = — 6 507,6 kJ. mole⁻¹.Boulègue Jacques, Fouillac Christian, Michard Gil. Dépôts minéraux à l'émergence de sources thermales sulfurées sodiques des Pyrénées Orientales. In: Bulletin de Minéralogie, volume 104, 5, 1981. pp. 661-668