A new investigation of the Permian Leman Sandstone Formation (LSF): suitability for underground hydrogen storage in the Rough field, Southern North Sea, UK

The Rough field in the Southern Permian Basin was originally a producing gas field, later repurposed for natural gas storage and now a target to be the largest hydrogen storage site in the UK. Despite this, few past studies have investigated the facies and mineralogy present in the sandstone reservoir, which is imperative to ascertain its suitability for hydrogen storage. We present new petrographic and facies characterizations of the Permian Leman Sandstone Formation (LSF), using core from the Rough field. Our detailed analyses include core logging, SEM-EDX and XRD analyses. This research provides a new reservoir characterization and introduces novel reservoir facies classifications supported by detailed petrography. We identify four facies associations: aeolian, fluvial, sheetflood and floodplain and find that each facies within the reservoir possesses different minerology. Certain minerals within these facies have the potential to react with hydrogen in some way causing the potential production of hydrogen sulphide, dissolution and reprecipitation of carbonate minerals and clay mineral transformations. These reactions are dependent on mineralogy and abundance, which varies throughout the mixed heterogeneous facies. After evaluating the petrography and potential mineral reactions, we conclude that Rough has potential to be a suitable hydrogen storage site but there is a level of unpredictability due to the heterolithic nature of the reservoir sandstones. This research highlights the importance of detailed characterization of heterolithic facies that occur in the Lower Permian stratigraphic interval in the Southern North Sea (SNS), especially along the western faulted margin. Such characterization is paramount for other sites under consideration for hydrogen storage.