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In this work, a new dual modality monitoring technique is presented to demonstrate its interest to investigate the salt precipitation dynamics induced by gas flow-through drying. It consists of imaging simultaneously a core flood using both Neutron and X-ray beams. A method to calibrate and process the two signals is presented. It takes advantage of the difference in attenuation between the two ionizing radiations to quantify the different phase saturations and compositions as well as the reduction of porosity caused by salt precipitation. A set of experiments has been conducted at the NeXT-Grenoble beamline of the Institute Laue-Langevin facilities (ILL, France). Experiments were conducted on a homogeneous rock sample of Bentheimer sandstone using dry nitrogen and a 100 g/L KBr brine. The two first experiments aimed to calibrate the dual modality for the different phases. The last two experiments have been conducted with a brine capillary contact maintained at the gas outlet. Experimental data have given new insights into the organization of the three phases (the brine, the gas, and the precipitated salt) when a salt bank is formed in the sample. These quantities computed using dual-modality imaging show great similarities with published work. The salt accumulation was used to estimate the flow rate of brine pumped through the capillary contact to compensate for the brine evaporation in the gas phase. Observations have shown that a reduction of the initial porosity in some sections of the sample by 12–14% was enough to trigger a gas draw-down characterized by the migration of the salt toward the gas inlet. In some conditions (low gas inlet pressure for example), the rise of the water could be fast enough to form a second salt bank higher in the sample. It has been observed that the formation of the second salt bank could spread the precipitated salt in a less damaging configuration for the gas flow, triggering a phase of gas build-up characterized by the withdrawal of the water. These phases of gas draw-down and build-up could alternate until the sample clogs.

National audience; En France, le programme Investissements dAvenir a permis de lancer la construction de « REFIMEVE+ », un équipement dexcellence qui vise à délivrer une référence de fréquence optique à une vingtaine de laboratoires répartis sur tout le territoire métropolitain, via le réseau Internet de RENATER.Cette nouvelle technologie dépasse de plusieurs ordres de grandeur les capacités offertes par le service GPS dans le domaine radiofréquence (RF). Une révolution est en marche, avec une finalité : ouvrir la voie à des applications inédites dans des domaines aussi variés que la métrologie, la physique ou la géodésie !

Flow of supercritical CO2-bearing fluids through a rock is a fundamental phenomenon which acts upon a great many geological processes ranging from seismic activity to formation of ore deposits. Atomic Force Microscopy scanning experiments allowed us to infer movement of supercritical CO2-bearing fluids through calcite crystals and relate it to natural decrepitation of nanoscale fluid inclusions. Calculated velocities exceed the rate of diffusion predicated via current vacancy models by several orders of magnitude implying that CO2-rich fluid movement through micro and nano-pore space may presently be greatly underestimated.

The injection of a gas phase through a water saturated porous medium can reduce the water saturation not only by displacement mechanisms but also by evaporation mechanisms. In the presence of brine, this process can induce salt crystallization and precipitation within the porous medium with a risk of permeability alteration. In the field of gas production and storage, the occurrence of such a phenomenon can have detrimental consequence on the well productivity or injectivity. In this work, we investigated experimentally and numerically the effect of dry gas injection on salt precipitation and permeability impairment. State of the art equipment designed for high throughput coreflood experimentation was used to capture the dynamic of salt migration using X-Ray radiography. A set of experiments have been conducted on a sample of Bentheimer sandstone (10mm in diameter and 20 mm in length) as well as a two layers composite sample with a significant permeability contrast. Experiments were conducted using Nitrogen and KBr brine with different boundary conditions (i.e. with and without capillary contact). Results showed that salt precipitation results from the interplay of different parameters, namely pressure gradient, brine salinity, capillary forces and vapor partial pressure. Experimental observations indicate that in the case of dry gas injection, salt systematically precipitates but permeability alteration is observed only if a capillary contact is maintained with the brine. We built a 2D flow model integrating two-phase Darcy flow, capillary forces, salt effect on vapor partial pressure, dissolved salt transport, as well as the different PVT equilibria needed to describe properly the systems. Once calibrated, the model showed good predictability of lab scale experiment and thus can be used for parametrical study and upscaled to the well bore scale.

We present a new method for direct determination of the Boltzmann constant by laser spectroscopy. The principle consists in recording the linear absorption in a vapour of an atomic or molecular line at a controlled temperature around 273.15 K. By eliminating the pressure broadening, we deduced the pure Doppler width which gives a first optical measurement of the Boltzmann constant k B . The present determination should be significantly improved in the near future and contribute to a new definition of kelvin.

es proprietes spectrales d'un laser femtoseconde ont ete exploitees pour realiser des mesures de frequences optiques de tres haute precision. Les mesures sont referencees a un etalon primaire situe a l'Observatoire de Paris et achemine au LPL par un lien optique. Plusieurs etalons de frequence, reposant sur des transitions electroniques ou rovibrationnelles de molecules, ont ete mesures avec des incertitudes relatives comprises entre 2x 10 -12 et 5 x 10 -14 La mesure de l'evolution de leurs frequences au cours du temps permettra de tester une eventuelle variation des constantes fondamentales.

Nous avons mis au point une nouvelle technique de mesure de frequence dans l'IR (autour de 30THz) utilisant le peigne d'un laser femtoseconde. La frequence optique est directement comparee a l'ecart entre 2 modes du laser femtoseconde, lequel depend uniquement du taux de repetition f r du laser femtoseconde. La frequence absolue de notre laser a CO 2 asservie sur une raie a deux photons de SF 6 a ete mesuree avec cette methode. Les premiers resultats montrent une deviation d'Allan de 3 × 10 -14 sur 1 s.