Even if a good impedance inversion can be obtained for these zones, it will be difficult to identify the sand bodies. The usual approach is a labor intensive and subjective process to interprete the sand bodies from impedance volume. Our new approach is to use Vsh and effective porosity as pseudo impedance for time depth calibration and inversion, as well as using impedance itself. The time depth relationship will be the same for impedance and pseudo impedance, but the wavelet will be different for impedance, Vsh based pseudo impedance, and effective porosity based pseudo impedance. Vsh or effective porosity based inversion provides better definition of the sand bodies, and the work of interpreting sand bodies is now mostly based on a cutoff with minor interpretation.
Effective porosity based inversion also provides softdata for building porosity model.
On the other hand, Vsh based inversion would show better prediction for Vsh, and effective porosity based inversion would show better prediction of the effective porosity, compared to impedance based inversion. Seismic processing is often targeting structure interpretation. For attribute inversion, more high frequency energy should be preserved and relative amplitude should be preserved. In practice, reprocessing is costly, therefore filter and reverse-filter may need to be applied to prepare the seismic data for inversion. Since well logs and geological interpretations are usually available, this preparation should take well logs and geological information into account.