For details about the program E2S-UPPA, please visit our website: http://e2s-uppa.eu/en/index.html From : September 1st 2018 to September 1st 2021
Title:
Experimental characterization and modeling of seismo-electromagnetic waves
Thesis abstract:A seismic wave propagating in a porous media generates electromagnetic (EM) wavefields through the so-called seismoelectric conversion. The EM contribution can then be divided into two different categories 1) a co-seismic transient electric field accompanying the seismic wave, 2) an electromagnetic wave generated by the conversion of seismic into EM energies at the interface separating two different porous media. The first EM wave follows the seismic and does not carry that much more information compared to the seismic whereas the depth-converted EM waves have potentially huge application in near-surface Geophysics since, for example, a water-oil contact would generate an EM seismoelectric conversion where the seismic field could be poorly sensitive to such an interface. The quantitative understanding of the conversion at interfaces is still poorly known and has only been seldom observed in the field and in a few laboratory experiments.
The first task of the PhD student will be to design, run and measure seismic and electromagnetic signals in a poro- elastic medium with the presence of interface(s) of various types and geometries. The seismic measurements will be performed by laser interferometry whereas the electrical potential measurements will be done with a mesh of electrodes buried in the porous medium. Once the experiments performed, he/she will analyze quantitatively the experimental measurements by comparing them with direct numerical simulations performed with an existing numerical code. She/he will then take in hand the poro-elastic code developed by the other PhD student also involved in the overall CHICkPEA program (see scientific context below) and use it in the various contexts studied within the laboratory experiments.
Finally, the PhD student will perform a theoretical and numerical upscaling of the experimental results to the field scale (exploration geophysics scale, few hundred meters), the ultimate goal being to run an acquisition at the field scale to strengthen the theoretical and numerical results obtained at the lab-scale.
The whole project is challenging from the experimental point of view since we propose for the first time to employ innovative tools for studying the EM conversion at interfaces. Numerically, the challenge is even bigger since it consists into matching real laboratory data with a full 3D quite complex poro-elasticity direct simulation. Eventually, the main thread throughout this experimental/numerical study would be to find and identify a measurement procedure to enhance the amplitudes of EM conversions at interfaces in exploration geophysics.
Key words:W ave propagation, porous media, seismoelectric, electromagnetic, laboratory experiments, exploration geophysics.
Funding:E2S scientific challenges project from the university of “Pau et des Pays de l’Adour” UPPA
