Geophysical characterizations of fluid flow and gas-hydrate systems of the NW-Svalbard and SW-Barents Sea margins

Abstract

The thesis consists of four parts and its four main objectives are: (1) to establish a potential link between serpentinization beneath a young sedimented-ocean ridge and carbon release and gas hydrate formation directly above it, (2) to understand the coexistence of free gas and gas-hydrate and to image the geophysical evidence for a geologically controlled gas hydrate, fluid migration pathway and seabed expulsion system, (3) to image the active fluid flow migration path-networks from deep hydrocarbon sources and to assess the distribution of shallow gas accumulation, and (4) to determine in detail the seismic velocity structure of the regions close to the landward limit of hydrate stability zone. The methodology implemented to realize this aims was achieved by integrating 3D seismic imaging, 1D velocity modeling to 2D seismic imaging and bathymetric and oceanographic data mapping. This PhD thesis presents results from four articles that glean into the fluid flow and gas-hydrate systems of the NW-Svalbard and SW-Barents Sea margins. The important results found during this research are: (1) new evidence for carbon release from the deep-seated source rock through the sediments above diapirism and methane capture in the inferred areas of serpentinization at the Knipovich Ridge, (2) new geophysical evidence for gas migration and geologically controlled gas hydrate system offshore NW-Svalbard, where several existing glacigenic debris flow units, which are spatially confined and influence gas migration pathways and hence, the location of gas leakage zones at the seafloor and (3) first findings of the formation of “tilted” bottom-simulating reflector in the SW-Barents Sea. They have formed due to variations in fluid flux along regions of deep-seated fault complexes causing a change in heat flow. The data also provides new evidence for the connection of deep-hydrocarbon and shallow gas hydrate, where existing fault complexes apparently act as pathways for the upward migration of fluids.