Expert System for Seismic-Stratigraphic Interpretation

J. H. Fang, A. W. Shultz, H. C. Chen

A tutorial expert system has been coded to perform seismic facies analysis. The expert system assumes the user's ability to delineate seismic sequences and facies units on a seismic section. Each seismic facies (unit) is characterized by reflection configuration, reflection continuity, reflection geometries at the top and bottom sequence boundaries, reflection amplitude, lateral relations, external form, and internal velocity. The last three parameters are not used in this version because they cannot be confidently evaluated from single two-dimensional profiles.

Seismic facies types recognized by this expert system are (1) shelf and platform, (2) shelf margin and prograded slope, (3) basin fill, (4) basin slope drape, (5) mounded, and (6) chaotic. Subfacies types can sometimes be distinguished but are not necessary for basic interpretation.

Description of a seismic section is facilitated by menu-based data entry which allows the user to break down each facies encountered into its constituent elements in terms of the characteristics listed above. Graphic displays illustrate typical reflection patterns, an aid to novice users. Linguistic variables (unlikely, very possible, etc) are employed to describe the presence of one or more features for each characteristic property. Degree of confidence for possible facies is computed from these variables by fuzzy arithmetic; all features are integrated in interpretation of the seismic profile.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.