Eocene sandstone intrusions in the Tampen Spur area (Norwegian North Sea Quad 34) imaged by 3D seismic data

The Eocene of the northern North Sea is characterised by fine-grained mudstones and isolated sandbodies. Three-dimensional (3D) seismic data reveal that the Eocene mudstones are intensely deformed by polygonal faulting and contain numerous discordant amplitude anomalies. The anomalies identified in the Tampen Spur area are similar to discordant anomalies previously described from the Eocene in the South Viking Graben and the Outer Moray Firth. Detailed mapping shows that the anomalies are often conical in three dimensions, with dimensions ranging from 100 to 200 m height and a few hundred metres to a few kilometres lateral extent. Well calibrations show that the anomalies arise from sandstones tens of metres thick encased in mudstone. The discordant amplitude anomalies are interpreted as large-scale conical sandstone intrusions fed from deeper Paleocene sandbodies. Individual conical intrusions may contain millions of cubic metres of sandstone and may provide fluid migration paths, potential reservoirs, and pose a drilling risk when exploring for deeper targets. (C) 2004 Elsevier Ltd. All rights reserved.