Integrated geothermal reservoir characterization in the North German Basin.

The North German basin characterizes challenges and unique opportunities of the geothermal reservoir because of the geological structure and geothermal potential. One of these challenges is the marine environments of Eocene deposits. This contains shallow marine environments where can changing sea levels lead to a variety of sediments from coastal sands to deep marine clays. Moreover, the uncertainty of reservoir features due to diagenetic processes over geological time can considerably change the original depositional characteristics of sediments. This study outlines a comprehensive investigation focused on classifying and analyzing shallow to medium-deep geothermal plays, mainly within the Brussels sand formation from the Tertiary sediments in the middle Eocene. We have selected this formation due to its appropriate thickness for geothermal reservoir studies and its lithological characteristics, previous studies have shown that the sediment sequence contains shale and sandy formation in Wilhelmshaven with a thickness of around 5 -130m. The approach that we are going to present in this study, leverages a combination of Geothermal, well, petrophysical well logs, and seismic data to build a rock model and perform a geothermal reservoir characterization in the area. A comprehensive investigation of the North German Basin's geothermal potential has been conducted, with a focus on the classification of play types. This classification is essential for understanding the range of geothermal systems present and their particular characteristics. The first stage contains the selection of areas with a geothermal potential based on the thickness of the formation, depth of the target formation, availability of 3D seismic data, the density of drilled wells, and the thermal gradient. Through a primary analysis and literature review, based on the aforementioned parameters, the sand bodies of the Brussels Formation were shown to be a suitable target for further exploration. Then it follows by a detailed analysis of underground temperatures of reservoirs in medium-deep depth. The dominant temperature of the geothermal reservoir in this depth and the selected target formation is expected to be classified as low, which can be suitable for heating purposes. These lower-temperature reservoirs are suited for district heating systems, especially when combined with heat pump technology. Heat pumps can raise the temperature of the geothermal heat to stages suitable for domestic and industrial heating. Then the integrated workflow of the temperature analysis and rock model investigation in this study can assist as a foundational framework for further detailed reservoir engineering studies and further economic assessment.