AVO response for a complex double bottom simulating reflectors model

• Published in: Current science (Bangalore) 2010-05, Vol.98 (10), p.1354-1358
• Main Authors: Rajput, Sanjeev, Thakur, N. K., Rao, P. P., Joshi, Anand
• Format: Article
• Language: English
• Subjects: Angle of incidence; Anisotropy; Fluids; Hydrates; Low speed; Modeling; Reflectance; Reflectors; RESEARCH COMMUNICATIONS; Sediments; Signal reflection
• ISSN: 0011-3891

In recent times, analysis of multi-channel seismic reflection data has indicated the occurrence of double bottom simulating reflectors (DBSR) in many parts of the world. DBSR in the hydrate-bearing sediments is an additional complexity in data analysis. The causative mechanism of DBSR, an indicator for the presence of gas hydrate, is still being debated extensively. To ascertain the characteristics associated with DBSR, we model its response in the presence of seismic anisotropy and frequency depending amplitude versus offset (AVO). We have incorporated a low velocity layer (presence of fluids) in the hydrated layer to generate DBSR. The study suggests that a low velocity layer (presence of fluids) sandwiched in the hydrated layer can generate DBSR. AVO response for resonating frequencies (10 and 20 Hz) in the considered layer thickness shows appreciable tuning effect for both BSR1 and DBSR. The reflection amplitude responses of BSRs associated with hydrate/free gas layers with anisotropic considerations are smaller compared to normal hydrate/free gas layers. The reflection response is chaotic beyond the estimated critical angles. The DBSR identified on seismic data in Green Canyon in the Gulf of Mexico; its characteristics and possible mechanism for its formation have been deduced based on the knowledge gained from the modelling. Our studies suggest that genesis of DBSR in the Gulf of Mexico is due to the presence of low velocity layer (fluids) within the hydrate layer.