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Amplitude-Versus-Offset Analysis in Presence of Dip

Jeffrey R. Resnick, Patrick Ng, Ken Larner

Although exploration targets often lie on or near dipping horizons, most studies of seismic amplitude variation with offset have assumed all reflectors to be horizontal. Amplitude-vs.-offset (AVO) analysis need not be restricted to such simple cases. The presence of dip, however, can pose difficulties for AVO analysis. Difficulties arise from: (1) errors in estimating parameters in AVO analysis that depend on reflection angle, (2) mixing of information from different subsurface locations within a common-midpoint gather, (3) the dependence of normal-moveout corrections on reflector dip, and (4) interference of reflections by mispositioned events. If these problems are not addressed in processing, the dipping events in AVO analysis can introduce artifacts that lead to erron ous interpretation. In dealing with problems posed by dip, either prestack partial migration or full migration before stack can be used. It is important to ensure that these prestack processes treat amplitude properly. When such care is taken, dip is removed as an issue in performing AVO analysis on data from areas with structural complexity.

AAPG Search and Discovery Article #91035©1988 AAPG-SEPM-SEG Pacific Sections and SPWLA Annual Convention, Santa Barbara, California, 17-19 April 1988.