Title: 3D lithofacies modelling and quantitative fault seal analysis in the Altmark region (North German Basin)

Jacob Waechter, Christian Olaf Mueller, Alexander Malz

Geological survey of Saxony-Anhalt, Germany

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-kp8x-7r44

Attributed 3D volumetric models are important tools for geothermal exploration, subsurface storage of natural gases and waste and for risk management (e.g. contamination of ground water or induced seismicity). Of special interest are lithological attributes, which reveal important evidence on characteristics of deep aquifers and reservoir rocks and support project planning.

Therefore, we created attributed 3D volumetric models, which base on a detailed 3D structural geological model of the Altmark region (North German Basin) comprising 31 horizons from base Zechstein to Quaternary. For this purpose, information from lithologic-paleogeographic maps was transferred to the volume models by defining categorial properties. Shale fractions could be qualitatively estimated from the petrographic descriptions and quantitatively confirmed using gamma ray logs. Subsequently, a fault seal analysis was performed on the basis of the lithofacies model. Calculation of the juxtaposition parameter and smear gauge ratio (SGR) provides information on the faults transmissivity and the clay smearing of permeable fault segments.

The resulting attributed 3D models reveal essential information on geometry and characteristics of deep aquifers and reservoir rocks, as well as potential fluid pathways or sealing functions across faults in the Altmark region. Furthermore, extracted lithological information and attributed fault cutoff lines allow a detailed representation of subsurface parameters and the fault network on 2D maps. The results thus form the basis for large information systems and databases providing FAIR and easy to use information for further planning and prospection efforts.

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