ABSTRACT

Time-lapse seismic data are frequently used to characterize reservoir changes during hydrocarbon production. Typically, comparing amplitude differences between processed data sets can provide an illustration of the change in impedance corresponding to fluid substitution. In order to determine a quantitative change in elastic properties (P- and S-wave velocities), full waveform inversion (FWI) can be used. In this study, elastic full waveform inversion in the time domain is applied to synthetic data to recover the velocity change. Two kinds of inversion strategies are presented: (1) conventional inversion approaches where the inversion is performed for each vintage and the results are compared, and (2) residual time-lapse waveform inversion (RTWI) where the residual time-lapse data are inverted. We first present the theoretical basis of RTWI and then test this method on synthetic data. Results from inversion of elastic permanent ocean bottom cable (OBC) data are used to show the successful recovery of the change in velocities and to demonstrate the differences between these approaches.

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