Bent Kjølhamar, Alexander Smith, Allan MacKay, Luca Limonta and Roberto Ruiz present new experiences using UHR3D data that enable geohazards and two dimensional features to be better understood and more accurately imaged.
Introduction
Geophysical technologies and workflows analysing multi-sensor data in the shallow subsurface for marine wind turbine installation are in rapid development. It is now possible to acquire all relevant sensor data simultaneously together with Ultra High-Resolution 3D data in a single pass integrated geophysical survey (Caselitz et al. 2025 & McKay et al. 2025). Seismic UHR3D data is a relatively new addition to the otherwise 2D dominated subsurface interpretation workflows utilised in offshore wind. This paper will present new experiences using UHR3D data over the classical UHR2D-based workflows. Especially geohazards like boulders, shallow gas, and sand channels are obvious, but also two-dimensional features like iceberg scour marks or faults are now better understood and structurally more accurately imaged.
The top 100 m below the seafloor, and typically at high latitudes with strong glacio-marine influence, is of super complex geology with short-lived structure and small-scale facies changes in sedimentology. As seen in recent UHR3D data, many important features and sedimentological facies changes are seen over just 100 m laterally. Therefore, the soil unitisation models defined in Integrated Ground Models (IGM) are evolving in both their detail and complexity. Often, we have a chaotic and non-reflective seismic facies where geo-technical (Geotech) measurements indicate distinct soil stiffness changes. Furthermore, the Geotech data and the seismic data, especially UHR2D, often have poor depth matching, requiring manual vertical shifts to one or the other. This makes the ground modelling work complex and time-consuming. UHR3D seismic data with highly resolved P-wave velocity volumes and depth imaging methods enable better depth correlation between the 3D seismic and geotechnical data. In addition, the 3D P-wave velocity volumes themselves offer new volume-based approaches discussed in this article.
Floating iceberg dropped boulders and iceberg scour marks are a topic that 3D seismic data has shed new light on. In both 3D time-slice and along 3D interpreted horizons, iceberg scour marks are easily seen and classified as such. Using Sub-Bottom Profiler (SBP) data, the two-dimensional image of scour marks has a close resemblance to a point diffractor or boulder and may be misinterpreted in the absence of 3D data (Limonta, et al., 2025). From UHR3D data, a diffraction imaging volume can be used to interpret migrated boulder diffractions and be used to distinguish robustly between point features such as boulders and other geological structures.
