The thermal field of the Upper Rhine Graben – Temperature predictions based on a 3D model

Abstract

The Upper Rhine Graben (URG) is one of the regions in Germany with promising potentials for deep geothermal energy production. As part of the EU-funded project “IMAGE” (Integrated Methods for Advanced Geothermal Exploration), we aim to understand the processes and physical rock properties that control the temperature distribution in the deep subsurface of the URG. Typically, numerical models are developed to predict the hydrothermal conditions and to reduce the risk of drilling non-productive geothermal wells. One major problem related to such reservoir-scale models is setting appropriate boundary conditions that define, for instance, how much heat enters the reservoir from greater depths. To address this problem, we first develop a lithospheric-scale 3D structural model that differentiates the main geological units of the lithosphere including the shallow sedimentary basin fill but also the configuration of the deeper crust and lithospheric mantle. Based on this model we solve the steady-state conductive heat equation to understand the first-order controlling factors of the regional thermal field. Furthermore, this regional thermal model provides the boundary conditions for smaller and higher resolved models of the basin fill, for which coupled heat and fluid transport is simulated in a next step. We present the methodological workflow, the developed 3D structural and thermal models, and assess how heat transport mechanisms in response to lithological and structural features on different scales control subsurface temperatures