Geophysical study in the German North Sea on multi-layered reservoir and barrier systems and fluid-migration systems by means of high resolution 3D seismic measurements

• Applicants: Professor Dr. Christian Berndt; Dr. Axel Ehrhardt
• Subject Area: Geophysics ; Geology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564898008

The necessity of CO2 storage in the deep subsurface is becoming more and more crucial in order to fulfil the reduction of CO2 emissions and to remove carbon dioxide from the atmosphere by natural sink enhancement or the use of negative emission technologies (IPCC, 2022). For any subsurface storage, it is important to have precise knowledge of the potential reservoirs, as well as the integrity of the barriers. Additionally, understanding the potential for seal-bypass systems is essential, whether caused by naturally induced faults, subrosion effects, deeply incised tunnel valleys, or anthropogenic pathways such as abandoned boreholes. Natural fluid migration of biogenic or thermogenic hydrocarbons can be observed and analyzed regarding the reliability of barriers. Seal-bypass systems, e.g. the interaction between faults, tunnel valleys, and abandoned boreholes, are crucial scenarios to analyse for any subsurface storage. In order to study this setting, we intend to carry out a high-resolution 3D seismic survey in the area of salt diapir Gwendolyn (SW branch of the Horn Graben). Here we observe two different potential reservoirs (Buntsandstein and Upper Cretaceous to Lower Paleocene carbonates), Mesozoic and Cenozoic barriers and an abandoned exploration borehole. In particular, subrosion structures caused by the dissolution and subsurface erosion of evaporitic Triassic intervals at the “Late Cimmerian Unconformity” will be investigated. The aim is to determine whether these structures represent a systematic weak link in the barrier integrity of the Röt Formation (Upper Buntsandstein), which serves as the primary barrier for Middle Buntsandstein reservoirs in the German North Sea. Within the Quaternary sediments, several tunnel valleys are present. Near salt diapir Gwendolyn, all these geological elements could be observed in close proximity in an area of approximately 150 km². By means of our high-resolution 3D seismic setup with two high-frequency sources (GI-Guns) and 2x 1200 m streamer cables with 6.25 m channel spacing, we are able to image reservoirs and barriers, faults and tunnel valleys in detail. An additional cross-shaped set of ocean bottom seismometers (OBS) will allow a reliable seismic velocity control, even in deeper strata. We will be able to interpret and map the characteristics of the reservoirs and barriers, along with fault systems that may enable fluid migration to the surface. The mapping results will subsequently be used to create a high-resolution 3D model that, for the first time, depicts a region with a potential multi-layered storage and barrier system along with its structural inventory in the German North Sea. The outcome of this study will support the understanding of reservoirs, barriers, fault systems, subrosion structures and tunnel valleys and how they interact in terms of fluid migration.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 2520: Infrastructure area - Research Vessels
• Co-Investigators: Dr. Sonja Breuer; Dr. Heidrun Louise Stück