Angle-dependent inversion

          
Synthetic seismogram tie for the low-angle (~10°) near-stack.  The synthetic seismogram was generated by using the impedance log curve.  The correlation seems to be reasonably good. Synthetic seismogram tie for the high-angle (~30°) far-stack.  The synthetic seismogram was generated by using the computed EI (30°) log curve.  The correlation seems to be reasonably good.  Notice the weakening of the amplitudes at the location of the orange arrows.

 

Top:  Segment of the acoustic impedance section (with the overlaid AI log) shows anomalously low values of impedance at the gas-producing zone (yellow highlighted zone).  

Below:  Equivalent segment from EI (30°) section showing the anomaly as much more pronounced. 
(Data courtesy:  PetroNorte, Colombia)