3D temperature modelling in deep sedimentary basins-A case study from Altmark region (North German Basin)

Accurate information on the subsurface temperature distribution is crucial for assessing a region's geothermal potential and upcoming project planning. However, previous temperature models mostly suffer from low resolution structural models and unknown temperature gradient -lithology relations. Therefore, this study presents a new strategy for subsurface temperature modelling, applied to the Altmark region (North German Basin). It is based on a detailed structural model consisting of 31 base horizons between earth's surface and Base Zechstein. 46 temperature logs were used for the derivation of mean temperature gradients for each model formation. The averaged temperature gradients vary between 20 and 56 K km-1 in the study area. To account for the strong influence of highly thermally conductive salt accumulations in the Zechstein Group, empirical models were developed in relation to Zechstein and supra-salt thicknesses. Temperatures were calculated using a one-dimensional top-to-bottom approach. The temperature model shows the dependencies of the temperature distribution in the subsurface on the thermal conductivities and thus the predominant lithologies of the model formations. Small-scale anomalies induced by salt pillows and diapirs lead to differences in the predicted temperatures of up to 15 K at same depth level. A comparison between measured and modelled temperatures showed that more than 90% of the temperature data deviations are below 5 K. The final model was compared with an existing large-scale model to evaluate the prediction quality.