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2015 - THMC - Master 2 - Vallier Bérénice

Vallier Bérénice

Diplôme préparé : Master 2
Sujet de stage : Modélisation de l’influence de la circulation géothermique sur la convection hydro-thermale à Soultz-sous-Forêts
Tuteur : V.Magnenet, J. Schmittbuhl

Abstract :The 2D numerical simulation of the geothermic exploitation over the natural hydrothermal convection at Soultz-sous-Forêts is developed on an idealized geological cross-section. The section contains six layers corresponding to the granite basement and the sedimentary structure. The reservoir is assimilated as a porous medium saturated with the single-phase brine. The porous medium involves a thermo-hydro-mechanical coupling. The physical properties for the brine and rock are taken dependent on temperature and fluid pressure. The numerical study is interested about a circulation between an injection well and a production one. The hydraulic parameters of the 2010 circulation at Soultz-sous-Forêts define the parameters of the numerical model. The solving of the thermo-hydro-mechanical coupling constitutive equations is carried out by the finite element software Code Aster. The current two-dimensional numerical simulations are able to reproduce the field data during the production phase nd temperature profiles measured in the wells. However the impact of the geothermic exploitation over the longevity of the natural hydrothermal convection is unknown. The numerical simulation doesn’t allow to reach the hydraulic regime between an injection well and a production one if they are located in the deep granite basement. Indeed the numerical model can’t represent yet all the complexity of the previously stimulated zone that connect the two open-holes. However, the idealized case for which the two ells are located in the upper and naturally fractured granite allow the simulation of the geothermic circulation. The disturbance of the temperature and pressure fields were respectively finished 2 and 54 days after the end of the simulated circulation. The quick pressure convergence could explain the few seismic events until two weeks after the circulation ending. Stationary thermal solution changes can be caused by the temperature disturbance of a longer exploitation if the natural state is only a metastable equilibrium. To conclude, the convergence indicators must be calibrated to be compatible with several time-scales of disturbances. Once we surpass these difficulties, the simulation could provide a direct model helping to the inversion of bore-hole measurements, induced seismicity monitoring and INSAR deformation of the ground surfaces. These field measurements will allow a better prediction of the consequences of the geothermic exploitation.

Rapport de stage

2 juillet 2015