Common Transmission Point (CTP) Gathers: A New Domain for Amplitude Variation with Offset

Analysis of amplitudes of transmitted waves (TAVO) is an extension of the conventional AVO analysis using amplitudes of reflected waves. In this study, we introduce the common transmission point (CTP) gather, which is a new domain that is convenient for TAVO analysis. A CTP gather is formed by binning traces that have the same transmission point across a layer interface. We use the proposed domain to invert the ratios Delta alpha/alpha, Delta rho/rho, Delta beta/beta, and beta/alpha in a model consisting of a gas channel nestled within an oil reservoir. The TAVO equations are fitted to amplitudes calculated by Zoeppritz equations within CTPs inside and outside the channel. Within each CTP gather, we use all traces with incidence angles less than 90% of the critical angle (if any) as TAVO approximations break down beyond this point. The proposed CTP TAVO analysis method estimated Delta alpha/alpha, Delta rho/rho, Delta beta/beta, and beta/alpha in the gas channel within 1% of their corresponding true values.

Automated summary

Analysis of amplitudes of transmitted waves (TAVO) is an extension of conventional AVO analysis. In this study, a new domain called common transmission point (CTP) gather is introduced for TAVO analysis, and it is applied to a model with a gas channel in an oil reservoir. The proposed CTP TAVO analysis method accurately estimates various ratio parameters.