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Application de la méthode du potentiel spontané à l'hydrogéologie: expérimentation sur modèle réduit d'aquifère

Abstract : Identifying the geometry and chemical evolution of underground flow constitutes a major objective in hydrology. Geophysical tools (such as the radar, the electrical and magnetic methods) can complement well-bore measurements. Spontaneous potential (SP) monitoring is particularly attractive, since the electric field in the subsurface results from hydraulic (flow) or chemical (diffusion, reactions) dynamic disequilibrium of the aquifers. The objective of this thesis is to isolate the individual contributions of these different couplings.
Laboratory experiments were performed to measure – in a separate and independent way – each of the electrical signals produced by the flow of a homogeneous fluid, the diffusion of a salt front in stagnant fluid conditions, the transport of a concentration front, and the acid-base and redox reactions. The main part of the experimental set-up is a rectangular tank of decimetric dimensions, filled up with sand, hydraulically connected to two independent reservoirs, allowing uni or bi-dimensional flow patterns to be generated. In order to measure the signal, reduced-diameter, unpolarizable, copper – copper sulphate electrodes were devised.
The results show that SP is capable of identifying the motion of concentration fronts. The electrical response to diffusion is caused by the junction potential. The response to advection is the sum of the junction potential and the variation of the electrokinetic signal owing to changes in the coupling coefficient as the fluid conductivity (advection of salt) or the pH (advection of acid) varies. When two fluids are mixed or react in contact with one another, examination of the SP curves in the different zones allows us to estimate the extension and temporal evolution of the mixing or reaction zone. The heterogeneity of the medium, either structural or chemical, seems to play a major role as well.
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https://tel.archives-ouvertes.fr/tel-00011461
Contributor : Alexis Maineult <>
Submitted on : Wednesday, January 25, 2006 - 12:12:29 PM
Last modification on : Thursday, April 23, 2020 - 2:26:28 PM
Long-term archiving on: : Saturday, April 3, 2010 - 7:33:07 PM

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  • HAL Id : tel-00011461, version 1

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Alexis Maineult. Application de la méthode du potentiel spontané à l'hydrogéologie: expérimentation sur modèle réduit d'aquifère. Géophysique [physics.geo-ph]. Université Louis Pasteur - Strasbourg I, 2004. Français. ⟨tel-00011461⟩

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