Feasibility of Full-Waveform Inversion for High-Resolution Imaging of Onshore Salt Domes: Case Study from Central Jutland, Denmark

The imaging of onshore salt-related features remains a persistent challenge in seismic interpretation due to the complex seismic velocity fields and wavefield interactions associated with salt structures. This study explores the feasibility of applying full-waveform inversion (FWI) to a high-resolution onshore seismic dataset acquired for the mapping of potential carbon storage targets within the Gassum region, Denmark, to improve velocity model accuracy and structural characterization of the associated salt dome. The 2D dataset, collected using a dual-element acquisition system combining large-spread nodal and densely-spaced streamer sensors, offers good spatial and azimuthal coverage, making it a suitable candidate for testing advanced inversion techniques.In this study, we apply FWI using a multi-scale approach to address issues such as cycle skipping and convergence, with initial models derived from ray-based traveltime tomography. By leveraging both low- and high-frequency components of the seismic data and adopting a systematic approach, this feasibility study aims to assess the extent to which FWI can resolve features such as stratigraphic onlaps, fault geometries, and thinning of roof strata above the salt dome. Early results suggest that FWI can enhance the resolution of velocity contrasts and detect velocity inversions, which may lead to improved imaging of previously unmapped features, including shallow and radially divergent faults and sedimentary pinchouts. Furthermore, the integration of FWI with geological data supports the hypothesis of asymmetric dome growth due to uneven loading during its evolution. Challenges such as cultural noise, crooked acquisition geometry, topography variations, parameter sensitivity, and the need for robust initial models remain key considerations.The study demonstrates the potential of FWI to advance the understanding of salt dome evolution and its implications for geological carbon storage (GCS) in the onshore halokinetic environment. Specifically, the ability to refine structural interpretations and resolve velocity anomalies is helpful for assessing the suitability of halokinetic domes as potential GCS sites. The methodologies tested here can be adapted for use in other salt tectonic settings, offering a pathway for more detailed subsurface characterization in resource exploration and energy transition applications.