Quick Look Techniques

Equal Spaced Contouring Methods

One of the first Quick Look Techniques to apply when evaluating a prospect is the method used to contour the map (mechanical, equal-spaced, parallel or interpretive). Many prospect maps are prepared using an equal-spaced contouring method. Of all the contouring methods available (Bishop 1960; Tearpock and Bischke 1991), the equal-spaced method results in the most optimistic structural interpretation. This method assumes a slope of uniform dip over a general area mapped.

The use of the equal-spaced method often results in unrealistic structure maps (Figure 1)

Fig. 1 with highs looking like bubble shaped structures and lows portrayed as having sharp cusps. Compare the maps shown in Figures 2a and 2b. Figure 2a

Fig. 2a

is a prospect map showing three proposed locations updip of existing wells. Notice that the map has been prepared using the equal-spaced contouring method which shows untested highs adjacent to existing wells (the elusive high that always escapes penetration of the drillbit).

Are the three prospective highs shown in Figure 2a real or the result of the mapping technique? Figure 2b

Fig. 2b

is an alternate interpretation using the same well data, but an interpretive contouring method which allows the mapper to incorporate his or her experience, understanding of the structural and depositional geology of the area, three dimensional geometry, imagination and skill to prepare a geologically reasonable interpretation. Notice that in Figure 2b, there is 1, not 3 prospective locations.

No one can really develop a correct interpretation of the subsurface with the same accuracy as a topographic map. What is more important is to develop the most reasonable and realistic interpretation of the subsurface with the available data.

Top of this page