Modélisation du comportement hydro-géochimique du Dogger ; soumis à la reinjection de fluids "chauds" ou "froids". Compte rendu d'activité pour l'année 2010.
Résumé
The Dogger aquifer is chosen due to the combination of its already confirmed geothermal potential and the availability of a complete data set. We try to predict reservoir property trends under heat exploitation, interaction between flow, heat transfer, transport, and chemical reactions in this deep aquifer: using in-house computer codes CHESS and HYTEC. We focus on changes in porosity and permeability within the reservoir. In summer, temperatures of injection fluids plan to reach temperatures of 95 ° C to 105 ° C. In winter, the fluid temperatures reach 40 ° C. Cooled and warmed water have respectively, higher and lower viscosity than the fluid reservoir. The warm front is about twice as fast as the cold front. These effects are partially followed by thermally induced mineral reactions. Initially, the speciation of minerals likely to be present within the system must be determined: as well as the initial thermodynamic state of the Dogger. Then we attempt to determine the identity of all minerals (and gas) involved in the active geochemical processes of the system. The interdependence of some minerals has been demonstrated. The evolution of secondary minerals, silicates, clays and alumino-silicates, concentrations seem to be insignificant. Dissolution and precipitation of carbonates and Anhydrite dominates in the vicinity of the injection wells. Only the behavior of those minerals is likely to change significantly the porosity of the reservoir. Predicted major changes are taking place on a 2 m radius around the injection wells.