Three-Dimensional Estimation of Geothermal Potential from Geological Field Data: The Limagne Geothermal Reservoir Case Study (France)

Abstract

This study presents a methodology for estimating geothermal potential from geological field data in a sedimentary formation. The first step is dedicated to better understand the geometry of geology of the target zone using various data such as field measurements, bore holes and geophysical data. These data are reinterpreted through the construction of a 3D geological model. Inconsistencies are checked and turned into a coherent 3D interpretation by using the 3DGeoModeller software developed by BRGM. The second step consists in investigating the geothermal potential of the area. The geological model is meshed into a 3D unstructured Finite Element mesh using meshing capabilities from GEOWATT AG. Realistic thermal boundary conditions are applied and temperature field is computed using the Finite Element code FRACTure. As a final result, the total amount of geothermal energy available for each aquifer is computed, and the geothermal potential (recoverable energy) is mapped over the entire model. This methodology has been applied to assess the geothermal potential of a clastic reservoir in the Limagne d’Allier basin (Massif Central, France) where the most interesting geothermal target is identified as basal thicksandstones overlying the crystalline basement. The total amount of recoverable energy in this aquifer is estimated to more than 500 PJ (1015 J) in the modelled area. The most energetic zones appear to be located at the north-western edges of the basin, where sediment infill is the thickest.