The Röt Halite Member of the Southern North Sea – a critical top seal for carbon dioxide storage in the Bunter Sandstone Formation

The Bunter Sandstone Formation is under consideration as a storage reservoir for carbon dioxide in the UK Southern North Sea, where the Dowsing Formation provides the top seal. Over much of the basin, an evaporitic unit known as the Röt Halite Member is present at the base of the Dowsing Formation. The Röt Halite is separated from the Bunter Sandstone by a thin mudstone unit equivalent to the Solling Formation of the Netherlands. Previous studies have suggested that the Röt Halite will provide an effective top seal for carbon dioxide storage on the basis that it is dominated by bedded halite (Heinemann et al., 2012; Williams et al., 2014). Despite this, detailed knowledge of the lithological heterogeneities and structural variations within the unit are lacking, specifically with respect to its potential to act as an effective seal for carbon dioxide. High-resolution correlation of petrophysical logs was conducted to provide an improved understanding of the distribution of individual halite cycles across the UK Southern North Sea. Seismic reflection data were then used to elicit information on post-depositional deformation styles, in an attempt to relate Röt Halite thickness and the number of individual cycles to the presence or absence of throughgoing faults.