| Title | Experimental Simulation of Mass Transfer During Limestone Alteration Submitted to a Gradient of Temperature and a High CO2 Pressure: the COTAGES Experiment |
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| Authors | Jérôme Sterpenich, Jacques Pironon, Judith Sausse and Aurélien Randi |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | CO2 storage, thermal gradient, limestone |
| Abstract | Injection of a fluid into a geological reservoir, either for geothermal purpose but also in the context of greenhouse gas storage, implies physical, mineralogical and geochemical transformation of the rock due to an obvious disequilibrium between the reservoir and the injected fluids. The disequilibrium is not only chemical due to the undersaturation of the injected solution with respect to the solid phases, but can be also of thermal origin because of the gradient of temperature between an injected cold fluid and a hotter reservoir. In this context, chemical reactions such as dissolution and precipitation of the minerals can occur playing a role on the porosity and permeability of the rock and thus on the fluid injectivity. In order to follow the possible mass transfer due to chemical reactions induced by a thermal gradient, we performed experimental simulations with the COTAGES autoclave. Experiments are carried out on an oolitic limestone from the Paris Basin (France), which is a good analogue of the Dogger formations used for geothermal exploitation and possible CO2 storage in France. The variations of pressure during experiment as well as the evidence of dissolution and precipitation of calcites show that an important mass transfer occurs. The results of experiments will be discussed in terms of global mass budget, mineralogical transformations and implications on the petrophysical changes of the reservoir rock in the vicinity of the injection well. |