ThermoBase – Development of basic thermal data for the evaluation of the temperature field of sedimentary sub-areas
Country / Region: Germany
Begin of project: January 1, 2023
End of project: December 31, 2025
Status of project: January 19, 2024
Fig. 1: Results of a surrogate model with absolute values against the depth of the geological model at the time t=120k years
Source: BGR
In the project ThermoBase, the Federal Institute for Geosciences and Natural Resources (BGR) and the GFZ German Research Centre For Geosciences are working on behalf of the Federal Company for Radioactive Waste Disposal (BGE) as part of a project consortium to compile basic thermal data for the evaluation of the temperature field in sub-areas with sedimentary host rocks in Germany.
The most accurate possible knowledge of the temperature field in the sub-areas is necessary as part of the representative preliminary safety analyses, in which the BGE develops a proposal for siting regions for surface exploration and in the further course of the site-selection process. The initial temperature in the potential host rock is important, for example, for both determining the required area and depth of the repository, for assessing the thermal conditions in the repository system and for analyzing expected developments with regard to the safe containment of radionuclides.
In the project ThermoBase, the GFZ will develop temperature maps for the sub-areas with sedimentary host rocks based on temperatures measured in boreholes, thermal rock parameters and data on the regional heat flow. The data base consists of collected data, which will be qualitatively re-evaluated, and new data to be collected.
BGR will conduct statistical numerical analyses of the temperature distribution for typical geological situations in Germany using generic geological models of different types of host rocks. The temperature field calculations are based on stochastic methods. Sensitivity analyses are used to identify the influence of varying ranges of thermal parameters (thermal conductivity, heat capacity) in geological units and also to test the impact of changing boundary conditions, such as the basal heat flow and the temperature at the surface, on the temperature distribution in the models. The objectives are, on the one hand, to estimate the relevance of the influence of thermal data for the safety-related assessment of repository systems and, on the other hand, to make statements on the effect of the penetration depth of permafrost during possible future cold phases.
These analyses will form a basis for both better forecasting the present-day temperature distribution in the subsurface for sub-areas with insufficient thermal data and defining necessary accuracy in determining thermal parameters in the context of site investigations.
The following questions will be answered:
(1) What influence does the choice of thermal model parameters have on the temperature at the repository depth and the permafrost penetration depth?
(2) What temperature differences can be expected in a study area based on plausible parameter variations?
(3) How relevant are varying ranges in thermal parameters and variable boundary conditions for the temperature development in the storage of heat-generating radioactive waste??