EXPERIMENTAL AND KINETIC MODELING STUDIES OF THE HYDROTHERMAL ALTERNATION OF A FONTAINEBLEAU SANDSTONE

The aim of this work was to improve the modelling of the chemical beha viour of core samples of porous rock during water percolation. Dynamic water-rock interaction experiments at 150-degrees-C were performed on samples of Fontainebleau sandstone with daily sampling of the fluids having reacted with the rock. Indeed, these fluids are found to be rep resentative of the water-rock interaction processes occurring within t he rock during the percolation. Apparently a dissolution steady-state is rapidly reached after only several hours. The mass transfers betwee n the rock and the fluid are well detected in solution. With respect t o the mineral phases, mass transfers remain small but amount up to 1% of the rock. The thermo-kinetic modelling approach was applied in orde r to test a scenario for the chemical reactions which have occurred in the rock during the percolation. The duration of reactions establishe d either experimentally or by simulations confirm that the chemical di ssolution reactions occur rapidly and that the extracted solutions are even saturated with respect to the quartz after half an hour of inter action.