3D-Facies and Reservoir Modelling of the Buntsandstein Reservoirs of the northwestern Thuringian Syncline
An integration of stratigraphic, sedimentological and structural characteristics of the Lower Triassic in the northwestern Thuringian Syncline (Thüringer Becken) has been performed. A stratigraphic-sedimentological model has been created for the Middle Buntsandstein Subgroup (Volpriehausen, Detfurth, Hardegsen and Solling Formation) and the structural model has been built from the top of the Zechstein Group to the top of the Middle Buntsandstein Subgroup. By integrating all available surface and subsurface information (regional geology, core logs, sample descriptions, electric log and structural interpretation) in a 3D-model using the software Irap RMS 2009 and KINGDOM suite version 8.2 allows to create a sedimentogical-stratigraphic-structural model. The Middle Buntsandstein Subgroup of the northwestern Thuringian Syncline consists of about fifteen (15) fining upward cycles that provide a high resolution lithostratigraphic framework. The cycles apparently reflect climate fluctuations between wet and dry periods driven by Milankovitch variations in solar irradiation. The cycles can be well correlated across the studied area. The successions of the Middle Buntsandstein are mainly characterized by continental clastic deposits reflecting the interaction of eolian, fluvial and lacustrine environments. Their total thickness varies between 130 and 230 m. In the Thuringian Syncline, NNE-SSW tensional and transtensional stresses acted during the Buntsandstein deposition creating subsidence patterns, uplifted areas as well as a regional angular unconformity. The main structural element in the study area is the Schlotheimer Graben. It comprises three main normal faults striking NW (305°) with stratigraphic throws from 20 to 280 m and two minor faults of similar strike with displacements of 20 m. On the Eichsfeld Swell uplift and erosion occurred after deposition of the Hardegsen-Formation, evidenced by the absence of Detfurth and Hardegsen-Formations. The 3D model allows to (re)evaluate the regional Buntsandstein architecture, thus contributing to the understanding of stratigraphic, tectonic and paleogeographic factors that controlled the evolution of the Thuringian Syncline during the Early Triassic.