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2014 projects

  • ‘MicXtreme’ Microbiology of the extremes : from the mineralosphere to the Soultz-sous-Forêts geothermal plant. (PI : G. Imfeld) The geosphere is linked to the biosphere : microbial communities are developing in and on the minerals, possibly impacting the kinetic of minerals dissolution and the chemistry of surrounding fluids. The MicXtreme project couples microbial and geochemical approaches to study the microbial communities colonizing minerals and the evolution of the mineral surface reactivity. The aim is to understand better how the biogeochemical process influence the capacity of geothermal sites. The development of techniques for the study of the colonization of the samples, in situ during one year, and the selection of protocols (molecular biology for DNA extraction, imaging..) permit to study the microbial communities and their relation with minerals and surrounding geothermal fluids. Summary
  • Hydrothermal alteration of K-Spar in the context of Soultz-sous-Forêts : effects of secondary phases and the Gibbs free energy reaction. (PI : D.Daval) The study of the K-Spar dissolution in a geothermal context is interesting for understanding the interaction kinetic between the water and the rock within the reservoirs. The acquisition and the treatment of the images during the experiments permit to study the dissolution velocity and the reactivity depending on the facets orientations. Collected data allowed the development of a preliminary model of dissolution for each facet in accordance to experimental observations, and also the development of a new chemical diffusivity measuring protocol that will be applied during the next experimental campaigns. Summary
  • Monitoring of a geothermal reservoir by hybrid gravimetry (PI J. Hinderer) The use of different types of gravimeters (permanent supraconductor gravimeter, absolute ballistic gravimeter and micro-gravimeter) permits to obtain spatial and temporal information on gravity variation at the surface, associated to the natural or anthropic functioning of a reservoir. Several campaigns were realized on the geothermal sites of Soultz-sous-Forêts and Rittershoffen. The numerical development allows to treat data collected during these campaigns. Thus, models are being elaborated, especially for the EGOGI site (Rittershoffen). Summary
  • Numerical modelling of the reactive transport of the geothermal fluid reinjected in the EGS reservoir at Soultz-sous-Forêts : chemical and isotopical evolution of the fluid and mineralogical transformations (PI Y. Lucas) The data collection on the mineralogy of the solid phases in the EGS reservoir of Soultz-sous-Forêts has permitted a geochemical definition of the geothermal fluid. Various numerical modelling have been done to study the evolution of the different mineral phases according to the temperature, and the dissolution/precipitation processes. Several on-going development will provide a precise modelling of the chemical and isotopic evolution of the fluid and of the mineral transformations Summary
  • Geological and structural study of the triasic sediments in the northern Rhine graben. Implications for the EGS projects at Soultz and Rittershoffen. (PI P. Duringer) During 2014, the correlation between the well-logging data (gamma-ray) and the mud-logging data (cuttings) at GRT1 and EPS1 (Rittershoffen and Soultz-sous-Forêts) was performed and provided a better characterization of the chronostratigraphic limits in the Tertiary and Secondary formations (sedimentary cover). The interpretation of the UBI log in the reservoir (granitic domain) has been realized before and after the hydro-chemical stimulation. These progresses in the geological and structural knowledge of the sedimentary cover were an important help for the ECOGI industrial project (GRT2 cuttings interpretation). These works are at the origins of several other projects, including a Ph.D thesis ADEME/LabEx G-EAU-THERMIE PROFONDE (J.Vidal). Summary
  • THM modeling of hydrothermal circulation in deep geothermal reservoirs (V. Magnenet) In the framework of a 2013 project, a first 2D reservoir model was created using an idealistic geological cross section of the Soultz-sous-Forêts geothermal site. The numerical hydro-thermo-mechanical (THM) simulation carried out with the finite elements software Code Aster (EDF R&D) reproduces with success the experimental convective temperature profile obtained in the GPK2 borehole. They also allow to export several vertical observables (strain, porosity, Darcy’s velocity…) and 2D maps. The model opens other research possibilities like the stability study of the convective solution obtained, which will be investigate in 2015. Summary
  • High precision leveling network around Soultz-sous-Forêts and Rittershoffen geothermal sites (G. Ferhat) The aim of this project is to observe the surface deformation around the geothermal sites of Soultz-sous-Forêts and Rittershoffen. In 2014, a high level leveling network has been set up and several measuring campaigns have been realized including a global one (by 15 students of the INSA) for the levels measurement, the levels determination of all the points of reference (also for gravimetry). The collected data has been compared to the 1973 and 1976 IGN data. Other measurement campaigns and publication are planned for 2015. Summary
  • Numerical modeling of fracture development during fluid injection (PI O. Lengliné) The aim of this project is to study the dynamics of a fault hosting numerous heterogeneous asperities. We propose to link the statistics of the induced seismicity of a geothermal reservoir to the burst of failures produced in our numerical model based on the elastic fiber bundle. It suggests a way to improve the knowledge of the fracturing process asperities are interacting. The study of the seismics events size and the adaptation of some of the parameters in the numerical code used for the analogical experiment simulation in laboratory gave interesting results, which are in publication process Summary
  • Thermal microcracking in rock (P. baud) The study of thermal microfracturation in rock is useful for the understanding of the impact of temperature on physical and mechanical proprieties of rocks, particularly for the monitoring of deep geothermal reservoirs. Several studies were focused on the granite properties. 2014 has been important for measuring instruments with the installation of the tri-axis mechanical press T500 and the extension of the “low pressure” permeameter for field measurements. Summary
  • Extending the KIT temporary seismological network of the Rittershoffen geothermal field. (PI E. Gaucher) 15 autonomous seismological stations and 7 telemetric stations have been deployed on the Rittershoffen geothermal site between March and June 2014. The operation permits to collect data during the drilling and the production tests of the GRT2 borehole, but also during the circulation tests between August and mid-November 2014. The data has been archived at EOST. Summary
  • Magneto-telluric monitoring of geothermal reservoir (“SMT-géothermie”) (PI P. Sailhac) The magneto-telluric monitoring provides images and a follow-up of the geothermal activity from a continuous measurement of magnetic and electric fields in the shallow subsurface. The data collected in 2013 have been treated and modelled. Several MT campaigns have been performed during 2014 on the Rittershoffen geothermal site. The regularity of the measurements allows to study the variations before and after the stimulation and during circulation periods. Summary
  • 250 temporary seismologic stations in the Northern Alsace (a strange idea ?) (PI J. Vergne) A temporal network of 250 seismological stations was set up in the North of Alsace. The compact and autonomous stations were installed according to a 2D homogeneous grid (a station each 1.5 km) around the geothermal sites of Soultz-sous-Forêts and Rittershoffen. One of the objectives of the project was the imaging of the first 5 kilometers of the crust using seismic noise correlation. The measurement campaign, which enlisted more than 15 persons, has been relayed in the regional newspapers. The collected data are being treated and will be part of several studies in 2015. Summary

13 avril 2015