Traveltime Tomography to Unravel the Chalk Group Structures at the Gassum CCS Site, Denmark

In carbon capture and storage (CCS) projects, it is important to investigate the seal properties, which often include the shallower part of the investigated area. Reflection seismic data in most of the Danish Basin appear less strong and coherent in the top 500 m, and hence reflectivity alone cannot be used to study the integrity of these potential CCS reservoirs. This study seeks to bolster and connect near-surface with deeper reflection seismic data by leveraging the capabilities of seismic traveltime tomography and other elements of seismic data. By exploiting the advantages of high-resolution, large offset data acquisition, the traveltime tomography method was adopted for detailed structural characterization of the Quaternary sediments and the Chalk Group in the Central Jutland region, Denmark. Specifically, a focus on the potential for CO2 capture and storage in this area is pursued by constructing accurate velocity models and integrating them into reflection data processing. Our study aims to enhance reflection images and correlate them with the traveltime tomographic results for an updated geological interpretation of the area. The subsequent findings demonstrate the effectiveness of the tomography method with major improvements in the reflection seismic sections that provide additional features for improved large-scale geological mapping. The combined integration of the tomography and reflection seismic sections reveals that salt tectonics influence the region’s topography. Adaptation of different velocity models shows significant alterations in the seismic imaging of the area that should be taken into consideration regarding the site’s capture and storage potential.