Geological 3-D model of the larger Altensalzwedel area, Germany, for temperature prognosis and reservoir simulation

In the framework of the German R&D programme CLEAN (CO₂ Large-Scale Enhanced Gas Recovery in the Altmark Natural Gas Field), the geological structure of an area encompassing the Altensalzwedel sub-field and its surrounding was analysed in detail. A 3-D model was developed that contains the major geological formations and their general lithology including the natural gas reservoir (in the Permian Rotliegend), the immediate cap rock (Permian Zechstein) of the reservoir and its overburden. Based on this geological model, a 3-D steady-state thermal model was generated as part of a shared earth model. The parameterisation of the geological model layers with thermal rock properties is based on laboratory and well-log data. The model shows temperature changes in dependence of geological structure and of different rock thermal conductivity. The calculated surface heat flow is high (>80 mW m⁻²) for most of the area, which is in accordance to measured surface heat flow. Temperature on top of the Rotliegend reservoir is variable ranging from 110 to 150 °C. The quantification of temperature changes versus depth as well as laterally in the reservoir are valuable input data for modelling the dynamic processes of CO₂ injection within CLEAN.