We analyze the characteristics and suppression of multiples generated in three dimensions. We derive expressions for the traveltime of peg-leg multiples generated by two dipping planes. Using this theory, we demonstrate that multiples generated in three dimensions may have traveltimes substantially different from 2-D multiples. For a case studied of 3 degrees cross-line dip, second-order water-bottom and peg-leg multiples arrive on the order of 10 ms earlier than they would in two dimensions. For fifth-order multiples, this difference is as high as 65 ms. These 2-D/3-D time differences grow to many hundreds of milliseconds for 10 degrees of cross-line dip. We confirm the presence of the cross-line dip effect in field data containing salt-related multiples. Using dips estimated from a 3-D interpretation of a top-salt horizon, we further demonstrate that the theory can accurately predict traveltimes for such multiples. Finally, based on the theory, we present an algorithm for suppressing 3-D multiples when cross-line dip can be estimated, validating the algorithm using model and field data.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview