Équipements

Detecting different water table levels in a shallow aquifer with combined P-, surface and SH-wave surveys: Insights from VP/VS or Poisson’s ratios

When applied to hydrogeology, seismicmethods are generally confined to the characterisation of aquifer geometry. The joint study of pressure- (P) and shear- (S) wave velocities (VP and VS) can provide supplementary information and improve the understanding of aquifer systems. This approach is proposed here with the estimation of VP/VS ratios in a stratified aquifer system characterised by tabular layers, well-delineated […]

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Publications, WP6 , , , ,

Inversion of generalized relaxation time distributions with optimized damping parameter

Retrieving the Relaxation Time Distribution (RDT), the Grains Size Distribution (GSD) or the Pore Size Distribution (PSD) from low-frequency impedance spectra is a major goal in geophysics. The “Generalized RTD” generalizes parametric models like Cole–Cole and many others, but remains tricky to invert since this inverse problem is ill-posed. We propose to use generalized relaxation basis function (for instance by […]

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Publications, WP6 ,

Interpretation of magnetic resonance measurements in the varying earth’s magnetic field

At the scale of a magnetic resonance sounding (MRS) field setup, the earth’s magnetic field in the subsurface may vary laterally with depth and over time. These variations can be caused by different natural factors and generally cannot be compensated for by accurate tuning of the measuring device. The varying geomagnetic field (GMF) causes non resonance conditions of excitation that affect the amplitude and phase of […]

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Équipements, Publications, WP6

Thermal-plume fibre optic tracking (T-POT) test for flow velocity measurement in groundwater boreholes

We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using distributed temperature sensing (DTS). The method uses a point heater to warm a discrete volume of water. The rate of advection of this plume, once the heating is stopped, equates to the average flow velocity in the well. […]

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Publications, WP3 ,

2D characterization of near-surface VP/VS: surface-wave dispersion inversion versus refraction tomography

The joint study of pressure (P-) and shear (S-) wave velocities (VP and VS), as well as their ratio (VP/VS), has been used for many years at large scales but remains marginal in near-surface applications. For these applications, VP and VS are generally retrieved with seismic refraction tomography combining P and SH (shear-horizontal) waves, thus requiring two separate acquisitions. Surface-wave […]

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Publications, WP6 ,

Contribution of the finite volume point dilution method for measurement of groundwater fluxes in a fractured aquifer

Measurement of groundwater fluxes is the basis of all hydrogeological study, from hydraulic characterization to the most advanced reactive transport modeling. Usual groundwater flux estimation with Darcy’s law may lead to cumulated errors on spatial variability, especially in fractured aquifers where local direct measurement of groundwater fluxes becomes necessary. In the present study, both classical point dilution method (PDM) and […]

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Publications, WP7 , ,

Traceurs isotopiques intégratifs (WP8.3.)

Critex

L’arrivée de Bryan CHAGUE en janvier 2015 sur le poste de CDD CRITEX au BRGM a permis de débuter le WP8.3. Ce WP vise le développement et le déploiement d’un système de prélèvement passif intégratif en forage, système devant permettre d’avoir accès à des mesures isotopiques dans les eaux souterraines en intégrant temporellement le signal. Nous avons développé un prototype […]

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Actualités, WP8

Tracer tests (WP7.3.)

L’objectif du WP 7.3 est de développer un laboratoire mobile permettant de mesurer les concentrations de traceurs et produits de réaction lors d’expériences in situ visant à caractériser la réactivité de la zone critique dans différentes conditions d’écoulement. Après l’aménagement du camion 4×4 de l’OSUR en 2014, l’année 2015 a été marquée par les premières campagnes impliquant directement le laboratoire […]

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Actualités, WP7

Mesures des flux et tomographie hydraulique (WP7.2.)

L’objectif des travaux menés au cours de l’année 2015 a été de développer des méthodes de tomographie hydraulique originales basées sur une sollicitation périodique du milieu. Le principe consiste simplement à faire varier la charge de manière périodique dans un forage et de suivre en parallèle les variations de charge dans d’autres forages ou d’autres sections de puits. Un signal […]

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Actualités, WP7
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