Characterizing hydraulic properties of the Upper Jurassic aquifer in Southeast Germany using simulated pumping tests of a complex multiwell geothermal site

• The Karst zone is the main driver of fluid dynamics in the reservoir, while fault zones restrict the flow. • Debris facies also contributes to the flow in addition to the matrix in the middle and top blocks. • Permeability has a stronger impact on the sensitivity analysis output function than specific storage. • Correlating the elementary effects with raw input parameters provides insights into parameter interaction occurrences. Precise characterization of a reservoir's hydraulic properties is crucial for the efficient utilization of deep geothermal resources. However, this task becomes particularly challenging in reservoirs with high heterogeneity, as such conditions complicate the parameterization of numerical models, which are key exploration components. Nevertheless, introducing such spatial intricacy to a model often leads to increased accuracy and enhanced predictive capabilities. To effectively represent these complex systems, numerical models must reliably emulate natural reservoir behavior. Among effective modeling techniques, pumping tests are particularly important for their capability to explain groundwater flow dynamics near geothermal wells. At multiwell sites, integrating data from interference tests enables the investigation of the reservoir far-field, leading to a better understanding of the reservoir characteristics, interwell communication, and overall flow conditions. In this study, a multiwell site operates in a highly heterogeneous reservoir comprising two major fault zones that divide the reservoir into three blocks, as well as multiple influx zones, including a karst zone, debris facies, and porous matrix. This research aims to identify the hydraulic role of each reservoir component through developing a highly detailed numerical model that can reproduce the wells’ interactions during pumping tests. This also includes ranking the importance of each reservoir component on groundwater flow using a robust sensitivity analysis. Influx zones in the middle and bottom blocks were found to exhibit the strongest impact on the reservoir’s fluid dynamics. Karst zones, in particular, were also crucial to accurately capture the interactions between the neighboring wells, whereas fault zones diminish cross-fault interferences.