Stack enhancement using the three‐term equation: Synthetic and real data examples

Abstract

The normal move-out8 (NMO) equation, = is exact for a. homogenous earth and works well in a layered earth for limited offsets. However as the maximum offset increases it starts to deteriorate. The three term equation, + = + is valid for larger offsets. This paper compares the two equations for both synthetic and real data. sets, and concludes that. where there are large velocity contrasts, the three term equation is capable of increasing the stacking amplitude by up to 9% for our real data set, and up to about 60% for the synthetic data, It also gives more accurate interval velocity estimates. The synthetic example has also shown the utility of the three term equation when performing standard AVO analysis with long offsets, since it better avoids amplitude variations due to kinematic effects. However as it has an extra variable to be scanned, the three term equation requires more processing time. By choosing a suitable sampling method it is possible to reduce this time, so that it only takes twice as long as standard NMO analysis, whilst still showing a reasonable increase in stacking amplitude.