Abstract：Sand bodies are rich in our study area of Bengal Bay.Most of them are offshore deepwater sedimentary channels and lobes.They represent high amplitude as bright spots,and lateral changes are fast.But not all of them contain hydrocarbon.Thus hydrocarbon detection is very important in the study area.The Aki Richards equation and Shuey equation are aplieded in this paper.Series of pre-stack AVO attribute cubes are calculated based on these equations,such as P-wave velocity,S-wave velocity,P-wave impedance,S-wave impedance,intercept(P),gradient(G),P×G,near offset stack amplitude,far offset stack amplitude,fluid factor,Poisson ratio and so on.The forward modeling,fluid substitution and petrophysical analysis with well data have been carried out.The corresponding amplitude characteristics are defined,and relevant AVO attributes are calculated,which serve as the basis for the later seismic AVO attribute analysis.The results of this research indicate that if a reservoir contains gas,the amplitude increases with offset,P-wave velocity,P-wave impedance,λρ and Poisson ratio all change fast.These features belong to AVO anomalies of type Ⅲ.And if a reservoir contains water,the above attributes only show tiny changes.In this paper,P×G,fluid factor,Poisson ratio,P-wave impedance and λρ are used for analysis.Many gas prospects have been detected in the study area based on this method.
