Seismic Characteristics of Gas Migration Structures on the North Atlantic Margin Imaged by High-resolution 3D Seismic

Dedicated Fluids and Fluid Flow. We have acquired high-resolution P-Cable 3D data on five sites in the North Atlantic revealing a variety of different fluid migration characteristics. Both the Vestnesa and Nyegga areas offshore Svalbard and mid-Norway are characterized by pockmarks and vertical pipe structures. Gas hydrates are present in these areas and a layer of free gas is trapped beneath the gas hydrate stability zone. Kilometer-sized mud volcanoes have been imaged in the Gulf of Cadiz (Mercator Mud Volcano) and on the western Barents Sea margin (Haakon Mosby Mud Volcano) showing a circular crater with chaotic infill surrounded by inward dipping reflections. The Barents Sea contains large accumulations of shallow gas. We have acquired data from two sites were shallow gas and gas hydrates are interpreted. However, no vertical pipe structures are identified in the imaged regions. The surveys show that high-resolution 3D seismic data are very useful for mapping shallow gas and gas hydrates, for increased offshore safety, and for understanding of fluid flow processes.