Spit-systems – an overlooked target in hydrocarbon exploration: the Holocene to Recent Skagen Odde, Denmark

Well-constrained depositional models are essential for successful exploration and field development. The Skagen spitsystem offers a unique possibility for the establishment of a depositional model constrained by excellent outcrops, well-defined palaeogeography, good age control and detailed observations on hydrodynamics and morphology of the prograding part of the spit-system. The model offers a supplementary interpretation of shallow marine sandstones to the existing delta and linear shoreface models. The sand-dominated Skagen spit-system is c. 22 km long, 4 km wide and up to 35 m thick, with a sand volume of c. 2.2 km³. If filled with oil, this system would contain 0.6 km³ corresponding to 3.8 x 109 barrels assuming a porosity of 30% and an oil saturation of 90%. This is comparable in size with the largest Danish oil field (the Dan field), in the North Sea. Reservoir models for isolated linear ‘offshore’ sandstone bodies have been controversial for many years. Their size and internal indications of palaeocurrent directions are similar to those of the spit-system model, and this model may therefore be applicable for some of these bodies.