Gas Hydrates and Shallow Gas Reservoirs in the Barents Sea and from the Svalbard Margins: from Unconventional Resource Or a Geohazard?

Stefan Bünz¹, Jürgen Mienert¹, and Shyam Chand^2
1Department of Geology, University of Tromsø, Tromsø, Norway.
²Norwegian Geological Survey, Trondheim, Norway.

The Barents Sea and the continental margin around Svalbard are large hydrocarbon-prone basins of the Norwegian Arctic region. A significant portion of the hydrocarbons has leaked or migrated into the shallow subsurface and is now trapped in gas-hydrate and shallow-gas reservoirs. Furthermore, there are few places on the W-Svalbard margin and the Barents Sea, where methane gas is leaking from the seafloor into the oceanosphere.

Gas hydrates are supposed to contain more carbon than does any other global reservoir. Their abundance on continental margins worldwide makes gas hydrates important as a possible future energy resource. Many areas in the Barents Sea indicate the presence of gas hydrates but the total amount of gas hydrates in this area is yet unknown. The gas-hydrate system offshore western Svalbard is far more extensive and includes the whole Vestnesa Rigde, a huge sediment drift north of the Molloy Transform. A strong cross-cutting BSR is visible. Gas hydrates probably occur mostly in the porous more sandy sediments of the contourite deposits. However, gas hydrates also constitute a major geohazard for the exploration industry and could play a role in global climate change.

The Norwegian Arctic region shows many places where gas occurs in shallow (< 400 m) strata. Particularly the Barents Sea has many areas with shallow gas reservoirs. Most of the gas is assumed to be leaking from Jurassic hydrocarbon reservoirs. Leakage of gas into the shallow sediments was probably a result of the profound Cenozoic erosion of the Barents Sea Shelf.

Accumulations of free gas in the shallow subsurface are considered a geohazard. They constitute a risk for safe drilling operations and they may pose a threat to global climate. However, the discovery of a large shallow gas field on the mid-Norwegian continental shelf shows that these accumulations may constitute a hydrocarbon reservoir with economic significance. This discovery adds a new play-type within the mature basins of the Norwegian margin.

This presentation gives an overview of the distribution of gas hydrates and shallow gas reservoirs in the Barents Sea and on the Svalbard Margins and assesses the economic potential of these unconventional resources. Moreover, we also address their significance as a geohazard, particularly with respect to a changing global climate in this environmentally-sensitive area.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia