Constraints on seismic reflections and mode conversions at bottom simulating reflectors associated with gas hydrates

Bottom simulating reflectors (BSRs) are the primary seismic signatures of subsurface gas hydrate accumulations. Inference about the presence of gas hydrates only from P wave data hampers realist assertion and the quantification of resource estimates. Owing to uncertainty about conversion of seismic...

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Bibliographic Details
Published in:Journal of petroleum science & engineering 2012-06, Vol.88-89, p.48-60
Main Authors: Rajput, Sanjeev, Müller, Tobias M., Clennell, Michael B., Rao, P. Prasada, Thakur, N.K.
Format: Article
Language:English
Subjects:
bottom simulating reflector (BSR)
Boundaries
Conversion
converted Shear Waves (PS)
double bottom simulating reflector (DBSR)
Gas hydrates
Green Canyon
Kerala-Konkan (KK)
Offshore drilling rigs
Reflection
Reflectors
Seismic engineering
Seismic phenomena
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Summary:Bottom simulating reflectors (BSRs) are the primary seismic signatures of subsurface gas hydrate accumulations. Inference about the presence of gas hydrates only from P wave data hampers realist assertion and the quantification of resource estimates. Owing to uncertainty about conversion of seismic waves at the BSR interface and its identification of shear wave signature in most of the conventional seismic surveys studies of BSRs as being wave conversion boundaries are relatively sparse. In view of arriving at synthetic response and validate the assumptions that BSR works as mode conversion boundary we for the first time generate seismic reflections data and identify different conversion modes in relation gas hydrate exploration. The modeling results suggest that the hydrate and free gas interface acts as principal boundary for mode conversion from compressional (P) waves into converted shear waves (PS). It also appears that wave propagation effects in the overburden significantly influences the P-wave amplitude of BSR. To validate the modeling results we analyze seismic data from the Green Canyon, offshore USA and the Kerala-Konkan (KK) basin, India. The presence of BSRs, enhanced seismic reflection below BSR, seismic chimneys and hydrate mounds are found as the key seismic indicators for the occurrence of gas hydrates. The occurrence of double bottom simulating reflector (DBSR) over Green Canyon, Gulf of Mexico, Offshore, USA is originated with the migration of free gas through discrete layers of fractured sediments.
ISSN:0920-4105
1873-4715
DOI:10.1016/j.petrol.2012.01.022