Seismic Resolution as Key to De-Risking Shallow Foundation Hazards: A Hesselø Case Study

Despite significant improvements in shallow marine-seismic imaging techniques in the last decade, it appears that the general ability to explicitly identify and de-risk shallow geohazards has not improved at the same rate. Currently, marine ultra-high-resolution surveys tend to be characterized by < 0.5m vertical resolution at or near the seabed. While this may be acceptable for broader study of shallow geohazards using seismic data, it does not have sufficient resolution for the very detailed information required for de-risking shallow hazards and the associated design and positioning of turbine foundations in offshore wind farms. In this case study from the Hesselo Offshore Wind Farm Site, we present a holistic approach from acquisition and navigation to seismic data processing, achieving < 0.2m vertical resolution at or near the seabed and precisely mapping near surface geology; in doing so, we can de-risk shallow foundation geohazards like boulders, shallow gas, faults, buried slides and slumps and palaeo-channels. In the last few years, Fugro has successfully acquired and processed significant amounts of 2D/3D data volumes using such tailored approaches, which not only allows for significant improvements in data quality due to enhanced horizontal and vertical resolution, but also a thorough understanding of the near surface geology.