Amplitude variation with incident angle inversion for Q-factors in viscoelastic media: A case study

At an interface separating two viscoelastic media, the variation of the reflection coefficient with the incident angle is associated with the quality factors (Q-factors) of both media; this sets up a theoretical foundation for Q-factor inversion by amplitude variation with incident angle (AVA). The AVA inversion for Q-factors was applied to a field example of a gas reservoir to detect gas. Considering that the AVA inversion is commonly performed to obtain P- and S-wave velocities in the previous interpretation of the field seismic data, a new AVA inversion process for Q-factors was designed. The existing P- and S-wave velocities were used as the reference phase velocities at the dominant frequency of seismic signals in viscoelastic media, and then the Q-factors for P- and S-waves were inverted from the isofrequency components of the partial angle stack gathers with known reference phase velocities. The application in the field example found that this process obtained stable inverted Q-factor results, providing more powerful evidence for reservoir characterization.