Quick Look Techniques

Contour Compatibility

Structure maps on multiple horizons are often created without regard to the three dimensional validity of the interpretation as a whole. This can result in closely spaced structure maps that imply radical changes in strike, dip or thickness in very short intervals (Figure 1). The mapped horizons in Figure 1 are only 90-95 feet apart, but the -7100 foot contours on the two maps look like they may cross just south of the map. This would make the deeper horizon shallower than the shallow horizon. In areas of steep dip, structure maps that are hundreds of feet apart can be miscontoured so that separate horizons cross each other.

Fig. 1

When reviewing maps, one excellent QLT is to overlay the maps and verify that any changes in structure are reasonable and compatible in three dimensions. In Figure 2, the closely spaced horizons have similar strikes and dips. In steeply dipping areas, a hand sketched cross section on the mapped horizons can quickly show contouring problems (Figure 3).

Fig. 2

Fig. 3

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