Karin Andreassen1,
Karl A. Berteussen2,
Juergen Mienert1,
Helge Sognnes2,
Kerstin Henneberg3,
Jan Langhammer3
(1) University of Tromso, Tromso, Norway
(2) PGS Reservoir, Oslo, Norway
(3) PGS Reservoir, Olso, Norway
Abstract: Multi-component seismic data in gas hydrate investigations
The presence of gas hydrates and free gas along the
Norwegian continental margin is well documented in reflection seismic data.
Results from this area suggest a correlation between hydrate instability and
instabilities of the margin. It is, however, in order to understand the
importance of hydrates for slope instability, necessary with reliable
information about concentration and distribution of hydrates and associated
free gas. Seismic methods seem to be the most promising approach for indirect
detection and quantification of hydrates. It appears that hydrates may be
detected by P-wave methods only if free gas exists at the base of the hydrate
stability zone, giving rise to a bottom
simulating reflection (BSR), but such
methods seem to fail in detecting gas hydrates where the BSR is absent.
In order to test if P-S converted waves can add any
significant contribution in the geohazard research, a seismic multi-component
sea bottom
line was acquired by PGS Reservoir over a well-defined BSR at the
back wall of the Storegga Slide offshore of Norway. Since the gas
hydrate-related BSR in this area has a different dip than the sediment layers,
reflected events caused by gas hydrates can be separated from events caused by
the sediment layers. Results from modeling the P-S conversions, from effective
medium modeling, and from 2-D modeling have been compared with the real seismic
data to estimate the amount of gas hydrate and associated free gas, and to
investigate the potential for using converted waves in the detection and
quantification of gas hydrates.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana