Sub-regional hydrothermal modelling of sedimentary reservoirs for high-temperature aquifer thermal storage potential exploration – Approach developed in PotAMMO

Abstract

For efficient and economically viable heat storage solutions, and to enhance their integration into the energy mix for the heat supply of district heating networks, assessing and optimizing the potential of sedimentary reservoirs for high-temperature Aquifer Thermal Energy Storage (ATES) is a key aspect. The PotAMMO project (BMBF, PtJ, FKZ: 03G0913B) methodologically integrates comprehensive geological exploration with dynamic hydrothermal modeling at the exploration phase for potential reservoirs and to provide realistic conditions for co-simulated ATES setup models (integrating district heating grids and subsurface thermo-hydraulic behavior). This integration is crucial for characterizing the potential of sedimentary reservoirs for high-temperature ATES, requiring sensitive parametrization of the boundary hydraulic conditions and thermal state of the reservoir. The exploration phase of PotAMMO emphasizes a thorough geological assessment, focusing on understanding the heterogeneity and complexity inherent in sedimentary environments. This phase includes detailed sedimentological and structural organization, which are essential for identifying potential reservoirs suitable for high-temperature ATES, along with their petrophysical and hydraulic properties. Thus, sub-regional dynamic hydrothermal modelling is a cornerstone of the PotAMMO approach, aiming to simulate the complex interactions between heat and groundwater flow within these sedimentary reservoirs for two locations: the central northern Upper Rhine Graben for integration into the Mannheim district heating network, and the northern termination of the Upper Rhine Graben for the target Offenbach. This modeling is essential for understanding how the dynamic nature of the hydrothermal regime and processes in sedimentary reservoirs can affect ATES potential, and provides insights on where to place ATES wells for system efficiency optimally. The sub-regional model, the core of this contribution, and the ATES local models are run in FEFLOW on the basis of Petrel-built grids and the district heating grid is simulated in Modelica. A simplified case study for the co-simulation is also presented here. This approach intends to overcome the challenge of integrating geological complexity and heterogeneity with the typically sparse data available for these environments and localities. Stochastic modeling is used to manage geological uncertainty and effectively interpolate data. This allows for a nuanced representation of the subsurface, enhancing the reliability of hydrothermal models and rock property distributions. By combining detailed geological exploration with advanced dynamic hydrothermal modeling, PotAMMO addresses the challenges of geological complexity, heterogeneity, and data scarcity. This approach is essential in paving the way for more efficient and realistic assessments of ATES potential, thereby contributing significantly to the advancement of sustainable energy storage solutions and their integration into large-scale district heating grids, for significant decarbonization of the heat supply.