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Salt tectonics and intra-salt structures of the Zechstein on- and offshore northern Netherlands

3DSEISMICannt-1 Kopie.jpgSalt structures illustrated in hydrocarbon-related publications mostly focused on the over- and underburden and depict the salt as a structureless, homogeneous mass. In contrast, mapping in the field, well data, and observations from salt mines revealed that the salt is complexly folded and that intra-salt layers of carbonates, anhydrite and clays (“stringers”) image the complex deformation of the evaporites. But these observations are always spatially limited and the internal structure of the evaporites is still poorly understood. However, the evaporites deformation plays an important role for the long-term prediction of waste repository sites, storage caverns and for drilling associated oil traps, still seriously hindered by unexpected pressure kicks from stringers and brines. In order to better understand and predict the complex geometry and structural development of the layered intra-salt, we analyse high-resolution 3D seismic data from the Permian Zechstein in the northern Dutch on- and offshore. We focus on the Zechstein 3 (Z3) “stringer” that consists of thick anhydrite and dolomite layers fully encased in the halite and mostly forming an excellent seismic reflection. As the stringer was intensely deformed during several tectonic phases, we observe complex and superimposed folding and boudinage of the stringer. Fold amplitudes and frequencies as well as the length and width of gaps from boudinage enable us to characterize different generations and orientations of deformation. While data clearly show that the 3D geometry of the Zechstein evaporates can be extremely complex and the internal structure and evolution of each salt structure appears unique, we work on a structural model of the Z3 stringer that also serves as a well-suited proxy to identify kinematic processes in the salt.

More information: http://www.ged.rwth-aachen.de/index.php?cat=Research&subcat=Salt_deformation&page=Salt_Tectonics

Associated researchers: Frank Strozyk, Alexander Raith (GED), Bianca Biehl, Lars Reuning, Janos Urai (GED)