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MORSE, JAMES D., Deformation, Inc., Boulder, CO, and DAVID A. GOLDBERG, Seismic Mavens, Boulder, CO

Extending SCAT: Additional Techniques for Identifying Domain Boundaries and Determining How Azimuth Frequency Distribution Varies with Depth

For accurate structural interpretation of dipmeter data, it is important to project well bores onto sections correctly. Current methods include the DVA and tangent plots of Bengtson's statistical curvature analysis techniques (SCAT). However, if the wellbore crosses domain boundaries, i.e., surfaces across which the projection type (cylindrical or conical) or structural axis changes, all current methods fail: the plots show composite patterns that are difficult to interpret, if not misleading. Thus, methods for detecting domain boundaries, so that data from different domains can be analyzed separately, become important. We have developed and extensively tested a rapid, graphical method based on a series of AD plots--plots of apparent dip in arbitrary directions vs. measured depth. (SCAT's T and L plots thus become AD plots in the T and L directions.) In addition, we have developed an algorithm for calculating the most likely L direction of a given data set. We apply this calculation to equally spaced intervals and show the results on a separate plot, thereby providing interpreters with another aid for detecting domain boundaries.

Another important requirement is to determine how azimuth-frequency distribution (AFD) varies with depth. The traditional method--displaying rose diagrams at equally-spaced intervals--has two drawbacks: first, interpreters must study this display carefully to understand how AFD varies with depth; second, rose diagrams themselves are often misleading. In contrast, only a quick glance at a stack of rectangular histograms is necessary for determining how AFD varies with depth; moreover, histograms always depict AFD faithfully.

AAPG Bulletin, v. 74 (1990), n. 5, p. 726

James D. Morse and David A. Goldberg are the founders of Computational Geology.