Impact of the lower Jurassic Dunlin Group depositional elements on the Aurora CO₂ storage site, EL001, northern North Sea, Norway

Abstract

Northern Lights is the CO₂ transport and storage component of Longship, the Norwegian full-scale CCS project. Injection is planned into an under-explored sloping saline aquifer in the northern North Sea, the Johansen and Cook formations of the Lower Jurassic Dunlin Group. To bridge the information gap, well 31/5-7 (Eos) was drilled. The comprehensive dataset acquired was fundamental to interpret the depositional environment and determine the scale and spatial distribution of heterogeneities, as input to 3-D models aimed at improving storage resource assessment and understanding the injected CO₂ plume behaviour over time. The interpreted gross depositional environments of the storage units are marginal- to shallow-marine, arranged in three successive fining-upwards intervals. The lower interval includes coastal deposits with mixed wave- and river influence, correlatable over a large distance, dominated by meso-scale heterogeneities. The middle interval records paralic deposits with a wave- and tidal- interplay generating higher vertical and lateral variability. The upper interval is interpreted as tidal-dominated, predominantly with cm-scale heterogeneities. The repeated fining-upwards trends are ideal for plume redistribution and efficient CO₂ storage, and the reconstructed lateral depositional trends associated with generally good properties indicate a high storage potential. The Eos well data enabled building the properties distribution model, highlighting the importance of well control for storage evaluation.