Facies‐based full‐waveform inversion for anisotropic media: a North Sea case study

Elastic full‐waveform inversion can increase the resolution of reservoir characterization using seismic data. However, full‐waveform inversion for realistic anisotropic media suffers from the trade‐offs between the medium parameters and strongly relies on the accuracy of the initial model. Here, we employ a regularization methodology that utilizes geologically consistent information to reduce the inversion non‐linearity and crosstalk between the parameters. The geologic constraints are obtained from well logs and interpolated along major horizons in the migrated image. The algorithm, designed for transversely isotropic media with a tilted symmetry axis, is applied to ocean‐bottom data acquired at Volve field in the North Sea. The facies‐based constraints help build high‐resolution velocity fields and accurately image the reservoir region. In particular, the developed algorithm increases the resolution of the P‐ and S‐wave symmetry‐direction velocities and other parameters at the reservoir level. The facies‐based inversion also provides robust estimates of density, which is inverted simultaneously with the velocity fields. Overall, even relatively sparse prior information proves to be sufficient for the proposed methodology to achieve a much higher spatial resolution than the unconstrained full‐waveform inversion.