Hydrogen storage pilot: geological characterisation of an onshore aquifer structure in Fife, Scotland

Energy storage technologies are required to support the rapid development and integration of intermittent renewable energy sources into energy systems. Large-scale hydrogen storage in porous formations presents the opportunity to balance seasonal variation in energy demand. This reservoir modelling study aims to establish dynamic capacity estimates for seasonal hydrogen storage. This study investigates a shallow (<1km) sandstone reservoir, of an onshore anticlinal structure in east Fife, Scotland. This storage evaluation supports the geographically proximal H100 pilot rollout of 100% hydrogen for domestic use in 300 volunteer homes (https://www.sgn.co.uk/H100Fife). The target reservoir comprises a partially explored Carboniferous aquifer, thus this study also addresses the challenge of establishing a workflow for the appraisal of storage sites with limited data availability. We aim to maintain low investment costs for this currently immature technology. A static 3D geological model was constructed in reservoir modelling software, PETREL (Schlumberger), informed by data obtained from legacy seismic surveys and from deep boreholes acquired in a hydrocarbon exploration campaign in the 1980s. A sedimentological study was undertaken on the well-known local and regional Carboniferous sedimentology from subsurface information and coastal exposures to characterise reservoir heterogeneity internally – a necessary step to address the large data gaps between sparsely available data points. The reservoir is conceptualised as a 60-70m channelised fluvial sand, with unreactive quartz-arkose mineralogy, interbedded with thin mudstone horizons. The top seal is characterised by silts and mudrock, comprising a widespread maximum flooding surface. Seismic and borehole data has enabled a 3D base case model of stratigraphy and structure. Combined reservoir and structure forms a finite element model exported to CMG’s GEM, used to assess dynamic capacity estimates. Our key research questions are: does the target reservoir exhibit sufficient capacity to support seasonal hydrogen storage based on scenarios informed by industrial experience; what are the cushion gas requirements and associated costs; and what are the key risks and uncertainties influencing capacity estimates. We plan a base case scenario using the most probable geological reservoir and will investigate sensitivity variations around the geology. Benefits from this study include: i) development of a workflow for the hydrogen characterisation of storage reservoirs and the management of risk, whilst minimising initial investment costs, ii) evaluation of cushion gas requirements in a layered reservoir with only a few degrees of dip. Our preliminary results of injection and production will be discussed.