Combined onshore and offshore wide scale seismic data acquisition and imaging for CCS exploration in Havnsø, Denmark

Strong global actions for climate change include carbon capture and storage (CCS) as a feasible solution to reach carbon neutrality and raise opportunities for detailed subsurface investigations. An acquisition set-up designed for onshore-offshore zones was maximized for a wide-scale high-resolution structural imaging and implemented to cover a domal structure of interest for CCS utilization close to the town of Havns�nmark). Challenges of a combined acquisition and processing of land and marine multi-sensor data along a 42 km seismic profile are analyzed, suggested solutions are applied and limitations discussed. On the onshore side, a nodal array and a seismic landstreamer system were simultaneously used while along the transition zone a marine seismic streamer and ocean bottom seismometers were added to record the seismic response generated by two seismic vibrator sources. The adopted sensing domains (velocity, acceleration, and pressure) were studied and different processing steps were evaluated to enable their processing and subsequent data set merging. Results suggest as a best approach, a separate prestack processing of the different data sets and the computation of new geometries and new surface-consistent residual static correction after their merging. The data acquired in the transition zone illuminate for the first time the subsurface geology of the region delineating an expected domal closure. The final seismic section shows high continuity of the reflections with good resolution along the entire profile, identifying the main reservoir structure and the surrounding areas, which are important to ensure the reservoir integrity and safe exploitation over longer time scales. Shallow and deep reflections are consistent with the stratigraphic column from a well-log near the profile. The presented study shows a comprehensive workflow for processing such a multi-sensor data set in onshore and transition zone settings.