Modelisation des aquiferes thermaux avec des methodes geophysiques integrees

Written work here was undertaken in order to investigate geothermal reservoirs associated with major faults, located in Caldes de Montbui, Spain, and Sardara, Sardinia. This thesis has two independent parts. The first is a theoretical profile of geophysical methods applied in this work. The second focuses on the development of a methodology for cross-validation between the electromagnetic model (EM), densities models, and models of resistivity. The development and application of this methodology were in two hydrothermal environments. To improve the knowledge of the structural context of thermal aquifers, different complementary techniques, audio magnetotelluric measures (AMT), Time Domain Electromagnetic (TDEM), Tomography of the electrical resistivity (ERT) and Gravimetry, were made around the two areas of applications. The important physical parameter identified by MT methods is the electrical resistivity, which is particularly sensitive to the presence and the mineralization of the water. The three-dimensional modeling of the data allowed us to define the depth and the extent of hydrothermal levels. Despite some limitations, the MT method has proved well suited to study geothermal sites. There are several geophysical methods that have become industry standards, but they should not be used in isolation. However, the resistivity method is very useful, because it is directly related to the characteristics of geothermal reservoirs. In addition, because of the terrain of most geothermal areas and the profound nature of the reservoir, the TDEM combined with MT resistivity methods are becoming the methods of choice for geothermal exploration.