2021-03 - PhD position: Experimental approaches of the Seismoelectric effects in a geothermal context

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E2S UPPA, an I-Site since 2017

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PhD position - Experimental approaches of the Seismoelectric effects in a geothermal context

Scientific context

The SEE4GEO (Seismoelectric Effects for Geothermal Resources Assessment and Monitoring) project brings together an international team composed of researchers of Laurence Livermore National Laboratory (LLNL, USA), the University of Hawaï at Manoa (UHM, USA), NORCE (Norway), TLS Geothermics (France), and the Université de Pau et des Pays de l’Adour (UPPA, France). The objective of the project is to develop a subsurface imaging technique based on seismoelectric effects technique (SEE), which is a new and innovative approach for geothermal subsurface imaging and monitoring at reservoir scale. We will assess SEE in terms of data acquisition, cost and quality, and determine its capability in comparison with classical imaging and monitoring techniques, particularly decoupled seismic and electromagnetic methods. We will focus on developing new numerical tools for forward and inverse modeling, and inform on optimized field survey, data acquisition and processing for deployment in many other exploration projects in case of success.

In the framework of this project, UPPA proposes two PhD positions:

  • Numerical analysis: the PhD student will be involved in developing of a fast, true 3D numerical package, handling SEE imaging and subsurface properties characterization, including resistivity and permeability. Identified scientific and technical challenges will be related to the diffusive and attenuated nature of SEE signals. Numerically, this will imply extra care for stability of our algorithms for forward and inverse calculations.
  • Experimental analysis: the PhD student will be involved in developing laboratory experiments. The goal of the study will be defining the best experimental setup for detecting permeable zones in geothermal systems. It will be led with a geophysical approach, including theoretical and instrumental analyses.

 

Description

Seismoelectric effects are a pore-scale phenomenon relying on electric charge separation created by streaming currents generated by pressure gradients, which occur when a seismic wave propagates (Pride, 1994). This defines seismic-to-electric conversion. The propagating seismic wave generates an electrical current, which in turn induces an electrical field. This electrical field is often referred to as a coseismic field, propagating with the seismic wave. When this coseismic field is disrupted by a heterogeneity (due to e.g. a mechanical, electrical, or pore-fluid contrast), an electric dipole is created, triggering an independently diffusing EM field that is instantaneously detectable and provides information at depth, and is referred to as the so-called interface response field. Although the signal-to-noise ratio of the converted seismic-to-electric signals can be challenging, SEE dataset can capture unique information on important geothermal reservoir properties and heterogeneities, such as resistivity, salinity, degree of saturation and viscosity (e.g., Smeulders et al., 2014), as opposed to purely seismic or purely electromagnetic records. Moreover, the SEE interface response fields created at changes in
properties can detect thin layers and other fine-scaled structural features such as fractures beyond the seismic resolution (e.g., Grobbe and Slob, 2016).

 

Workplan: experimental analysis

Laboratory experiments using a proxy setup to geothermal rock properties will be performed to provide datasets to test the developed SEE imaging capability. Enhanced signal-to-noise ratio data acquisition and data processing techniques will be developed as well in order to design and optimize field scale measurements. In the last decade, the experimental geophysics group of UPPA has been developing original and innovative experiments for the characterization of porous media (Bordes et al., 2006, 2008, 2015; Holzhauer et al., 2015; Devi et al., 2018). All facilities, available for this project, aim at observing the effect of petrophysical properties (porosity, permeability, saturation) on mechanical and electromagnetic wave propagation. As a hybrid seismic-EM method, SEE is a long-time specialty of this group, at the heart of the research activities in the laboratory or in the field. This original method needs strong instrumental developments since traditional devices are not designed for this very specific phenomenon. The aim of this PhD is to focus on the ability of seismoelectrics to localize permeable zones around boreholes. At the laboratory scale, we will experiment interface conversions for various conditions, using experimental proxies of geothermal rock.

In order to achieve these experimental goals, we plan to advance according to the following steps:

  • quantify seismoelectric coupling in permeable faults and their dependence on salinity and temperature;
  • study the interaction of an elastic medium with a porous zone (fracture/fault);
  • improve data processing in order to enhance the interface response;
  • improve the SEE instrumentation in order to measure electrical potential in a very high impedance context.

By comparing laboratory data and numerical computations, we aim at reaching the best design of field data experiments and providing quantitative interpretation of data. Instrumental developments will
substantially improve the signal to noise ratio, and are expected to open new opportunities at the field scale by upscaling the high-quality experimental results obtained at the lab scale.

References :

  • Bordes, C., Jouniaux, L., Dietrich, M., Pozzi, J. P., & Garambois, S. (2006). First laboratory measurements of seismo‐magnetic conversions in fluid‐filled Fontainebleau sand. Geophysical Research Letters, 33(1).
  • Bordes, C., Jouniaux, L., Garambois, S., Dietrich, M., Pozzi, J. P., & Gaffet, S. (2008). Evidence of the theoretically predicted seismo-magnetic conversion. Geophysical Journal International, 174(2), 489-504.
  • Devi, M.S., Garambois, S., Brito, D. Dietrich, M., Poydenot, V. and Bordes, C. (2018) “A novel approach for seismoelectric measurements using multielectrode arrangements: II—Laboratory measurements”. Geophys. J. Int. (2018) 214, 1783–1799
  • Holzhauer, J., Brito, D., Bordes, C., Brun, Y., & Guatarbes, B. (2017). “Experimental quantification of the seismoelectric transfer function and its dependence on conductivity and saturation in loose sand”. Geophysical Prospecting, 65(4), 1097-1120.
  • Pride, S. R., (1994), “Governing equations for the coupled electromagnetics and acoustics of porous media.” Phys. Rev. B, 50, 15678–15696.
  • Smeulders, D.M.J., Grobbe, N., Heller, H.K.J., Schakel, M.D. (2014), “Seismoelectric conversion for the detection of porous medium interfaces between wetting and nonwetting fluids)”. Vadose Zone Journal, 13(5), 1-7.
  • Grobbe, N. and Slob, E.C. (2016) “Seismo-electromagnetic thin-bed responses: Natural signal enhancements?”. Journal of Geophysical Research - Solid Earth, 121, 2460-2479.

 

Working conditions

Host Laboratory: Laboratory of Complex Fluids and their Reservoirs, Pau, France.

From the nanometer to hundreds of kilometers, from the nanosecond to a million years, from the physics and chemistry of interfaces, through the thermodynamics of fluids under flow, to reservoir geology, geomechanics and geophysics, status as an “industrial” UMR (Joint Research Unit), supervised by TOTAL, the CNRS and the UPPA, the LFCR is an innovative and remarkable research unit in more ways than one. Its specific focus, essentially based on the study of fossil georesources, and totally in phase with the local socio-economic context, sets it apart regarding applications and enables it to host internationally-recognized teams.

The LFCR is a joint research unit attached to the UPPA, the CNRS and TOTAL. It is organized into four research teams:

  • “Interfaces and dispersed systems” led by Daniel Broseta
  • “Thermophysical properties” led by Hervé Carrier
  • “Geomechanics and Porous media” led by David Grégoire
  • “Characterization of geological reservoirs” led by Daniel Brito (CRG)

The PhD student will join the CRG team (40 people, 17 PhD students), which aim is to analyze properties and characteristics of geological reservoir systems. Reservoir systems can be considered on a scale ranging from a meter to several kilometers and are the geological interface that enables the integrated analysis of all the processes at play in the construction of a sedimentary basin. The processes involved are played out at basin scale and right down to that of the pore network, linking solid rock and fluid layers. The team’s activities combine geological approaches (structural geology, sedimentology, geochemistry, geomorphology and neo-tectonics) with geophysics, rock physics and mineralogy.

The PhD student will benefit from the supervision/support of the experimental Geophysics group: Clarisse Bordes (Associate Professor), Daniel Brito (Professor) and from the interaction with the applied mathematical group : Helène Barucq and Julien Diaz (Research directors at INRIA).

Starting Date: September 1st, 2021

Duration: 3 years

Gross salary: 1 878 € / month (which includes extra gratification for teaching duties – 32h per year)

 

Profile

The candidate should be graduated in Geophysics, Earth Sciences, Acoustics or Physics (theoretical and modelling) and should also have a strong predilection for experimental work.

Particulars skills are sought in seismic and signal processing, elastodynamic modeling, poro-elastic modeling, seismic/acoustic propagation, electromagnetism.

Hands-on experience in Matlab, Scilab or Python is essential.

Fluency in English is mandatory. Basic French is necessary (free French courses are available).

Interest in teaching: the PhD student might be involved as teaching assistant in our Bachelor and Master programs (32h/year).
Bachelor of Earth Sciences is taught in French. Part of master of Petroleum Engineering is taught in English.
The teaching assistant will have to manage exercises and practical sessions in general Geophysics, basic Computing, Petrophysics.

 

Application

Requested documents:

  • CV
  • Cover letter presenting the motivation of the applicant
  • Master degree grade transcripts and ranking
  • Reference letter
  • Contact details of at least two people, from you work environment, who can be contacted for further reference

Selection process:

  • Establishment of the selection committee
  • Evaluation of the applicants' file
  • Interview with the selected candidates and ranking

Application files will be evaluated based on the following criteria:

  • Candidate's motivation, scientific maturity and curiosity
  • Candidate's knowledge in geophysics and computing
  • Grades and ranking during your Master degree, steadiness in your academic background
  • English language proficiency
  • Oral and written communication skills
  • Candidate’s ability to present her/his work and results

All application files must be sent to Clarisse Bordes: clarisse.bordes @ univ-pau.fr

Application deadline: June 1st 2021