| Abstract |
Geothermal exploration aims at locating favourable areas for exploitation. To reach this goal, various disciplines are implemented. Among the most common ones are geology, geophysics and geochemistry. Data are generally acquired in the field, such as geological observations, gravimetric surveys or thermal sources sampling. These data are interpreted to characterize the geometry, and the properties of the studied zone. They provide separate but complementary information to understand the area explored. However, combining geological, geophysical and geochemical interpretations is not an easy task. In such a context, one of the main difficulties lies in how to mix all this information to infer a coherent geothermal conceptual model. Merging them in the same space can help their combination to lead to a consistent understanding. First of all, this methodology allows to check the location of separate figures and to ensure their coherence. Moreover, it makes possible to build an overall interpretation based on various information. GeoModelling in 3 dimensions is an interesting candidate for this job because it allows to input materials from various origins to achieve a geological model. GeoModelling provides a common platform for interpretation during the exploration phase of a geothermal project. The final model can be completed through successive stages bringing new information at each step. For instance, a preliminary 3D model can be based on very rough data from bibliography, even before any fieldwork dedicated to the exploration. In a second time, geological data can be observed in the ground and incorporated in the model to refine the interpretation. The process can be continued using a gravimetric survey to improve the model at depth. Then, magnetotelluric resistivity can be injected in the model to infer possible fluid occurrence. Finally, location and properties of geothermal springs can be displayed in the 3D model to complete the interpretation. This kind of interdisciplinary workflow leads to a coherent conceptual model filled by geology, geophysics and geochemistry. Making a 3D model by associating complementary interpretations is an interesting perspective but giving them the opportunity to interact is even powerful. Indeed, geological, geophysical, and geochemical interpretations are not disconnected. Even if a preliminary work has to be carried out separately by each discipline, the interpretation coming from one can be fed by the others instead of putting them one after the other in a sequential workflow. To do so, the methodology has to be object oriented, where the central object is the conceptual geothermal model. In this light, the 3D model benefits from a common interpretation implemented jointly by geologists, geophysicists and geochemists. In other words, they can compare, connect, discuss, and adapt their own approaches for a mutual result on a GeoModelling platform. At the end, the conceptual model is not a conglomerate of distinct interpretations but a consensus shared by the contributors. The methodology described above will be illustrated with examples to demonstrate how 3D GeoModelling is helpful to infer a democratic interpretation during the exploration phase. In addition, the model can be enhanced during the next phases, when new data are acquired, to provide an up-to-date image of the investigated region. Such a 3D model can also be used to mesh the modelled geometry of the zone and to compute dynamic simulations. |