Seismic depth imaging using combined dual-element data sets for geologic carbon storage investigations in Thorning, Denmark

Abstract

The success of seismic depth imaging in sedimentary basins affected by salt tectonics depends as much on the illumination of complex geological targets as on our ability to transform mere data into images that we consider to be an accurate structural description of the Earth. Achieving this level of precision on land is by no means simple. This study presents a tailored depth imaging workflow that combines novel landstreamer and nodal 2D seismic data sets acquired for geological carbon storage site investigations above the Thorning salt pillow in Denmark. The dual-element configuration provides dense near-offset coverage alongside long-offset recordings, thereby enhancing the resolution of the shallow velocity field and improving illumination of both near-surface and deeper reflectors. The combined processing workflow addresses differences in geometry, amplitude, phase, and statics between the two data sets. Early-stage merging of these data sets transforms the two partial views into a single, unified image, thereby providing the basis for PSDM (prestack depth migration) of the combined data. The resulting depth image delineates a fault system along the southwestern margin of the Gassum Formation reservoir and deformed suprasalt strata with high resolution. Subtle structural discontinuities are identified in the overburden, and Quaternary paleovalleys are observed in the shallow subsurface, with implications for seal integrity and groundwater systems. The combined data enable improved velocity model building and enhanced imaging of key geological boundaries and structures from the shallow subsurface to depths exceeding 5 km. These findings demonstrate the potential of combining dual-element land data and tailored processing workflows for high-resolution imaging in structurally complex onshore environments.