| Title | Paris Basin's Thermal Characterisation of Tectonic-Heat Flow Modelling |
|---|---|
| Authors | Damien BONTE, Jan-Diederik VAN WEES, Laurent GUILLOU-FROTTIER, Vincent BOUCHOT, Olivier SERRANO |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | temperature, tectonic modelling, Paris Basin, geothermal energy |
| Abstract | The determination of deep temperatures in a basin is one of the key parameters in the exploration of geothermal energy in sedimentary environment. This study is a collaboration between TNO and BRGM and is part of the CLASTIQ-2 project. The aim of this work is to present a 3D-model of the present day temperatures in the Paris Basin. With that objective, we use a thermal-tectonic forward modelling method, calibrated using subsurface temperature values. The temperature measurement dataset is essentially composed of BHT (some 2443 values). These BHT measurements required correction due to the thermal disturbance created during drilling. After correction, which was carried out using the Instantaneous Cylinder Source (ICS) method, 494 corrected BHT values were available for the modelling of the Paris Basin. In addition to these BHT, some 15 DST measurements that are considered as close to the thermal equilibrium (i.e., ±5°C) were added to the temperature calibration values. According to this dataset of BHT and DST, the average gradient in the Paris Basin was calculated as 34.9°C/km with a surface temperature fixed at 10°C. The temperature values collected were then used to calibrate the tectonic-heat flow modelling. The model is based on the stratigraphic and structural evolution of the basin at the lithospheric scale but focus on the temperature in the sedimentary basin fill. The modelling takes into account the geodynamic evolution of the last 20 My, the heat production, and the specific heat conduction of each defined sedimentary layer as well as variations of the Mohorovièiæ discontinuity depth and thermal behaviour of the lithosphere. The result of the modelling is a 3D thermal block that we present as isodepth maps. The isodepth temperature maps show the strong influence of the thermal conductivity variations on the sediments, while faults may create some more localised influences. The thermal variations in the Paris Basin are also strongly influenced by crustal sources and variations of lithospheric base. The Alpine Orogeny created a slight temperature increase in the south-eastern part of the basin in relation to compressive uplifting. The other source is the lithology's inhomogeneities of the basement, generating additional sources of variation in the sedimentary sequence. |