The northernmost Adriatic Sea: A potential location for CO2 geological storage?

In 2009, the National Institute of Oceanography and Experimental Geophysics (OGS, Italy) has performed a geophysical survey in the northernmost sector of the Northern Adriatic Sea, between the Tagliamento and Po river deltas, with R/V OGS Explora. About 820 km of 2D multichannel seismic and Chirp profiles, together with multibeam data along the ship tracks, have been acquired, with the aim to reconstructing the Plio-Quaternary stratigraphic and tectonic setting of the study area. Data have been also analyzed to verify whether this region is suitable for CO2 geological storage. Sites eligible for the application of Carbon Capture and Storage (CCS) techniques have been already identified in the Adriatic Sea, except in the northernmost sector, due to the scarcity of available data. The analyses of the new OGS seismic dataset highlighted the occurrence of peculiar seismic anomalies, represented by sub-vertical wipe-out zones, that have been interpreted as due to gas leakages affecting the Plio-Quaternary sequence. They could be possibly related to the formation of rock outcrops interpreted as methane-derived carbonates. It is suggested that gas migrates along sub-vertical chimneys throughout the Plio-Quaternary sequence. The correlation of these sub-vertical features among the seismic profiles reveals that two main alignments could be recognized: a NW–SE trend offshore the Venice Lagoon and a NE–SW in the northernmost part of the investigated area. It leads to hypothesize that the preferential conduits for gas migration are associated to tectonic lineaments. The analysis of the tectonic setting has been then addressed at defining the role of fault/fracture zones, which can affect the integrity of a CO2 storage complex in this area. Tectonic features have been identified in the Mesozoic–Paleogene succession, but their relationship with the shallow faults/fractures representing the paths for gas leakages still need further work and additional data in order to be clearly constrained.

► A regional geological setting of the northernmost Adriatic Sea is presented.
► The occurrence of possible gas leakage zones has been identified.
►  The orientation of the gas leakages would be consistent with onshore fault systems.
► A potential area suitable for CO2 geological storage has been identified.
► The relationship between the leakage zones and the CO2 storage complex is discussed.