Ensemble-based reservoir characterization using time-lapse seismic waveform data

Assisted history matching methods are beginning to offer the possibility to use 4D seismic data in quantitative ways for reservoir characterization. We use the waveform data without any explicit inversion or interpretation step directly in an ensemble-based assisted history matching scheme with a 3D synthetic reservoir model. For this purpose a seismic simulator was developed to simulate the full waveform response to reservoir changes due to production. We discuss the iterative ensemble methodology, including additional steps that were found to be helpful in obtaining an ensemble that is properly conditioned to the initial base survey and maintains sufficient and reliable spread during the model updating process. The strength of combining the information contained in the waveform data with the prior information contained in the initial ensemble is visualized by means of ensemble covariances. The results of two history matching experiments show that more detailed features of the true permeability field can be reconstructed when production data are combined with time-lapse seismic data.