Derisking offshore windfarm installation by sub-seafloor boulder detection based on dedicated seismic diffraction imaging

In order to confront climate change and reach the ambitious goals set at COP 26, established renewable energy sources like wind and solar need to expand to new frontiers. For wind, the transition to offshore environments poses unique opportunities and challenges. While offshore wind farms promise more energy efficiency, their construction demands larger investments in foundations and infrastructure. Glacial movement that transported material over the various epochs has resulted in a liberal distribution of problematic boulders in exactly the kind of areas now proving ideal for the deployment of wind farm technology. This is especially evident in large stretches of the Baltic, North Sea and North Atlantic on the east coast of North America where boulders, carried south through glacial movements during the ice ages, pose significant hazards for the construction of new offshore infrastructure. To be able to carry out subsea construction work with reduced risk, a novel ultra-high-resolution (UHR) seismic measurement system has been developed by the Fraunhofer Institute for Wind Energy Systems IWES, Bremen, Germany, and the University of Bremen, Germany. The Manta Ray G1 that has been developed is specifically designed to detect and localize these small-scale objects in marine sediments with high accuracy using seismic diffraction imaging. As these boulders pose an obvious problem for the construction work it is the ability of the system to commit to dedicated object detection, e.g., for glacial boulders, integrated into a detailed ground model of the uppermost section of the subseafloor in challenging shallow-water regimes that offers a highly advantageous solution to the problem. The system uses a unique new survey methodology for the de-risking of offshore construction sites.