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Vuataz, François

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Vuataz, François
Affiliation principale
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Ancien.ne collaborateur.trice
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https://libra.unine.ch/handle/123456789/152

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  • Publication
    Accès libre
    Preliminary Modelling of the Permeability Reduction in the Injection Zone at Berlin Geothermal Field, El Salvador
    (2010)
    Portier, Sandrine
    ;
    Vuataz, François 
    ;
    Barrios Martinez, Antonina Luz
    ;
    Siddiqi, Gunter

    The exploitation of the Berlin geothermal field (El Salvador) started in February 1992 with two 5 MW electrical units. In December 1999, exploitation at a larger scale started with the operation of two turbo-generating condensation units of 27.5 MWe each. Since the beginning of exploitation until today, all the deep thermal fluids produced during the generation of electricity have been injected back to the reservoir. However, the well injectivities declined because of self-sealing processes of fracture thereby reducing permeability in the injection zones.

    Our study focuses on the factors that may have caused the observed loss of injectivity of reinjection wells, using numerical simulation of fluid flow with coupled chemical reaction modelling. Such a model helps quantitatively understand the complex interplay of thermal, hydraulic and chemical processes (THC) and to predict the impact of reinjection on reservoir properties. The first preliminary simulation was carried out with FRACHEM code. This paper presents simulation results that reproduce in some way the observed decrease of permeability in the injection zone with time.
  • Publication
    Accès libre
    Modelling Acid-Rock Interactions and Mineral Dissolution During RMA Stimulation Test Performed at the Soultz-sous-Forêts EGS Site, France
    (2010)
    Portier, Sandrine
    ;
    Vuataz, François 
    The Soultz EGS reservoir’s response to chemical stimulation is assessed by numerical simulation of coupled thermo-hydraulic-chemical processes. To assess chemical interactions between host rocks and a mixture of HCl and HF as well as its potential effects on the Soultz EGS reservoir, new modelling efforts using the FRACHEM code have been initiated. This paper presents the model calibration and results. Simulations consider realistic conditions with available data sets from the EGS system at Soultz. Results indicate that the predicted amount of fracture sealing minerals dissolved by injection of a mixture of acids (RMA) was consistent with the estimated amount from the test performed on GPK4 well at Soultz EGS site. Consequently reservoir porosity and permeability can be enhanced especially near the injection well by acidizing treatment.
  • Publication
    Accès libre
    Developing the ability to model acid-rock interactions and mineral dissolution during the RMA stimulation test performed at the Soultz-sous-Forêts EGS site, France
    (2010)
    Portier, Sandrine
    ;
    Vuataz, François 
    L’impact de la stimulation chimique sur le réservoir du Système Géothermal Stimulé (SGS) de Soultz est évalué par simulation numérique des processus couplés thermo-hydraulique-chimique. Les modélisations 2-D simplifiées du réservoir ont pour but d’interpréter et de prévoir les interactions acides-roche dans le granite fracturé du système géothermal stimulé de Soultz-sous-Forêts. Pour évaluer les interactions chimiques entre la roche hôte et un mélange de HCl et HF, ainsi que les effets potentiels du traitement chimique sur le réservoir SGS de Soultz, une nouvelle calibration du code FRACHEM a été intégrée. Les résultats de la simulation indiquent que la quantité prévue de minéraux dissous par injection d’un mélange d’acides Regular Mud Acid (RMA) est comparable au montant estimé lors du test de stimulation chimique du puits GPK4 sur le site SGS de Soultz. Par conséquent, la porosité et la perméabilité du réservoir peuvent être améliorées près du puits d’injection par la stimulation chimique., The Soultz Enhanced Geothermal System (EGS) reservoir's response to chemical stimulation is assessed by numerical simulation of coupled thermo-hydraulic-chemical processes. To assess chemical interactions between host rocks and a mixture of HCl and HF as well as its potential effects on the Soultz EGS reservoir, new modelling efforts using the FRACHEM code have been initiated. This article presents the model calibration and results. Simulations consider realistic conditions with available data sets from the EGS system at Soultz. Results indicate that the predicted amount of fracture sealing minerals dissolved by injection of a mixture of acids Regular Mud Acid (RMA) was consistent with the estimated amount from the test performed on GPK4 well at Soultz EGS site. Consequently reservoir porosity and permeability can be enhanced especially near the injection well by acidizing treatment.
  • Publication
    Accès libre
    Chemical stimulation techniques for geothermal wells: experiments on the three-well EGS system at Soultz-sous-Forêts, France
    (2009)
    Portier, Sandrine
    ;
    Vuataz, François 
    ;
    Nami, Patrick
    ;
    Sanjuan, Bernard
    ;
    Gérard, André
    Rock matrix stimulation is a method of enhancing well production or injection within a broad range of challenging environments, varying from naturally fractured limestones to sandstones with complex mineralogy. A common and often successful stimulation option, matrix acidizing, utilizes acids that react and remove mineral phases restricting fluid flow. Reviewed is the technology of chemical treatments available for oil, gas and geothermal wells and the key elements and results of the chemical reservoir stimulation program at the Soultz-sous-Forêts, France, Enhanced Geothermal System Project.