We present a study of the inneralpine basin of Hopfgarten focused on the analysis of basin fill in order to reveal its formation in relation to paleo-ice flow and tectonics. The study is based on geological mapping as well as seismic (reflection and refraction) and geoelectrical surveys. The oldest sequence in the basin, identified by seismic stratigraphy at 400 m below surface, consists of coarse grained sediments of supposedly Oligocene to Miocene age, which subsided along faults linked to the Inn fault. Three superimposed sequences, each displaying baselaps in contact with a subglacially formed unconformity and sigmoid foresets, show pleniglacial conditions followed by a glaciolacustrine environment. The uppermost of these three sequences lies on top of last glacial maximum till (LGM; Würmian Pleniglacial; MIS 2) and represents Termination I. The middle sequence is classified as Termination II following the Rissian Pleniglacial (MIS 6). The oldest glacial sequence cannot be constrained chronostratigraphically but might correlate with Termination V following the major glaciation of MIS 12. Limited glacial erosion during the LGM occurred only during the ice build-up phase. Further overdeepening was impeded due to topographic barrier and mutual blockades of glaciers within this highly dissected landscape. The occurrence and relative timing of the impediment was controlled by the onset of transfluences and thus by the altitude of coles. The higher amount of overdeepening during older glacial periods is explained by longer phases of free ice advance in the ice build up phase due to higher transfluences routes at that time. Thus, the preservation of older Pleistocene sequences within the basin may be the result of the lowering of watersheds from one glaciation to the next. Our model of an inverse relationship between glacial shaping of the surface and the subsurface may apply to similar Alpine landscapes as well.

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A fully integrated reservoir modelling approach aiming for the best conditioned static model for an underground gas storage facility (UGSF) in a complex structural and depositional setting is presented. The Nussdorf UGSF is a depleted gas field characterized by typical deep-water depositional environment settings including sediment mass-flow systems being shed off the emerging Alpine thrust front during the Neogene. The key challenge in assessing this specific storage performance is the communication within the individual stacked sandstone layers, as well as determining the existing cross-flow between such layers through wells and due to juxtaposition across faults. Highly heterogeneous reservoir facies, representing thin-layered, stacked sandy fans embedded in marly shale, were realized by joining object-based and Gaussian simulations constrained by a gross depositional environment model. Modelling known pressure communication across intrareservoir faults required fault throws to be adjusted at scales below the limit of seismic resolution. Scoping simulation runs on a best-guess model led to a full back-loop of the geological modelling. Several loops revealed that iterations limited to property realizations were insufficient, requiring additional modifications of the structural model. Only via this expensive approach could a geologically consistent and ‘fit for purpose’ reservoir model for the UGSF be achieved.