Pre-stack Time-lapse Seismic Attributes Analysis in Tau-P Domain

Abstract

In this paper, an algorithm to compute time-lapse time shifts in tau-p space for pre-stack CMP gathers is presented. The approach is used to estimate the so-called R-factor that enables relating relative velocity changes to vertical strain changes, and hence calculate both velocity and thickness changes within the reservoir and the overburden. We apply a ray-based method to generate synthetic waveforms for a four-layer reservoir model and apply the tau-p CMP algorithm on these synthetics to calculate time-lapse time shifts for each layer. We compare estimates of velocity and thickness changes with the true four-layer reservoir model. Unlike other methods for calculating time-lapse time shifts, the presented method utilizes pre-stack data and so avoids errors/uncertainties involved in conventional time-lapse seismic processes, such as cross-correlation for time-shift and migration velocity model uncertainty.