3D Seismic Coherence Mapping: A Technological Breakthrough

John A. Lopez, Mike Bahorich, Norm Haskell, and Susan Nissen

Amoco has developed a new coherence algorithm which, when applied to 3-D seismic data, provides a new and sensitive seismic attribute for enhancing the imaging of geologic features. Map view images of the coherence attribute readily depict faults of all magnitudes, diapirs, and other lateral discontinuities with a level of detail greater than traditional seismic data. The technique can also delineate subtle stratigraphic features. For reconnaissance, the coherence algorithm can be applied in a time-constant window without any prior interpretation. For example, coherence slices of a 360 square mile speculative seismic survey from the South Marsh Island area in the Gulf of Mexico dramatically depict the regional fault pattern over the entire survey area, as well as detailed channel morphologies. A second example from the Ship Shoal area demonstrates the complex structural evolution above a salt canopy near the Mahogany sub-salt discovery. Such map-view coherence slices are far superior to typical seismic amplitude time slice; however, vertical coherence sections are not superior to traditional vertical seismic amplitude sections. This suggests that the ideal horizontal seismic attributes are different from the ideal vertical seismic attributes. Significant interpretational advantage is realized when the ideal pair of attributes is combined in a single 3-dimensional display, such as a chair diagram. The use of this type of display on an interpretive workstation allows one to see ahead and to interpret ahead while scrolling through the seismic volume. With th use of the ideal horizontal and vertical attributes, interpretations are faster and more accurate.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California