Distribution and Stratigraphy of the Neogene Utsira - and Hutton Sand in the Viking Graben Area, North Sea

Gregersen, Ulrik¹, Peter N. Johannessen², Gary Kirby³, Andy Chadwick³, Sam Holloway⁴ (1) Geological Survey of Denmark and Greenland, Copenhagen, Denmark (2) Geological Survey of Denmark and Greenland (GEUS), Copenhagen NV, Denmark (3) British Geological Survey (4) British Geological Survey, Nottingham, United Kingdom

In the northern North Sea, three regional seismic surveys and more than 200 wells with geophysical logs have been used in order to outline stratigraphy and to map Miocene and Pliocene sands, in connection with the Saline Aquifer CO2 Storage project – a cooperation of seven energy/oil companies and five research institutions. The sandy quartzose parts of the Utsira Formation, the Middle Miocene to Late Pliocene Utsira Sand, extends North – South along the Viking Graben near the UK/Norwegian median line, for more than 450 km between 58°N and 61°40N, and 75–130 km East–West. The Utsira Sand is located in four distinct seismic depocentre units, and the succeeding shale-dominated Plio-Pleistocene deposits are divided into four seismic units. The Utsira Sand reaches thicknesses up to c. 300 m in the southern depocentre and 200 m in the northern depocentre. The Utsira Sand was supplied both from the East Shetland Platform area and from the Southwest Norwegian margin. The sands were transported into the basin areas and mixed with glauconite, especially in the northern area. At the eastern rim of the Shetland Platform, a major eastward prograding sandy system containing lignite, the Hutton Sand unit, supplied sands into the outer to middle Neritic Neogene sea strait over the Viking Graben area, where marine currents and other processes reworked and redistributed the sands into elongated bodies of the thick Utsira Sand depocentre units. The sand distribution mapping may have implications for well planning and the use of CO2 storage.

Keywords: Utsira Sand, Neogene North Sea