The role of a salt pillow in deep saline aquifer integrity and shallow groundwater resources

Salt pillow growth leads to the deformation of the suprasalt strata and can affect geological carbon storage in saline aquifers. A concern for storage sites on land is the drinking water because the impact of the deformation on fluid pathways and groundwater systems needs to be studied. Here, we present new seismic data from a potential carbon storage site in Denmark. A high-resolution seismic dataset was acquired using a strategically deployed nodal array and a landstreamer to assess the effects of the Permian Zechstein salt migration on the layers above a salt pillow. We create a geological model of the subsurface through correlation of reflection data with borehole data and investigate the main Upper Triassic Gassum Formation reservoir. Our findings reveal a fault system linked to salt diapirism and evidence of salt pillow growth from the Triassic into the Miocene. We image up to 2 km-wide Quaternary palaeovalleys, which incise the deformed overburden and serve as key groundwater aquifers. These results have implications for fluid transport in deep saline aquifers above the salt pillow, and for clarifying the deformation impact on the shallower groundwater systems.