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Abstract

In geothermal reservoir characterization and basin modeling, often conclusions are drawn and decisions are made using uncertain or incomplete data sets. Particularly, there are limited hydrogeological data in the Berlin area in the North German Basin. The groundwater in this sedimentary basin is divided into a shallow freshwater aquifer (with about 500 m depth) and a brackish to saline groundwater aquifer within deeper sedimentary layers. Between these two different groundwater compartments, a natural hydrogeological boundary is provided by the presence of an impervious clay-enriched layer (Rupelian Clay), which is discontinuous, eroded or not deposited in some local areas. Thereby, the distribution of hydraulic conductivity of Rupelian Clay aquitard that represents a vertical and horizontal partitioning of the aquifers below Berlin is of main importance in groundwater management. We use an inverse modeling approach to estimate the spatial distribution of hydraulic conductivity of the Rupelian Clay aquitard, using available local data within the Berlin province. We use a commercial finite element fluid flow simulator that interfaces to a parameter estimation package. A Gauss–Levenberg–Marquardt algorithm is used to adjust the hydraulic conductivity of the aquitard such that the hydraulic head observations are reproduced. Subsequently, the updated hydraulic conductivity of the Rupelian Clay is used as input to the forward modeling, in order to estimate the pressure and temperature fields. The results of the inverse modeling suggest a more continuous distribution of the Rupelian Clay layer below the Berlin area in comparison with previous published studies. Hence, the convective heat and fluid flow are more restricted, and there is less interaction between shallow and deep aquifers. Change in the predicted temperature field is more pronounced for deeper strata.