Stratigraphic traps may consist of three distinct zones: (1) downdip oil-water transition zone, (2) economic oil productive zone, and (3) updip waste zone (Dunham). As only one of these zones is economic, exploration efforts for stratigraphic traps should be geared toward determining if any show in a wildcat well is in one of these three zones of a trapped accumulation. If a well is thought to have drilled into the transition zone, calculations can be made as to how far structurally updip a well should be drilled to locate economic oil-water ratios. If a well is drilled in the economic zone of a trap, calculations can be made from the first wildcat well to estimate the downdip limits of the field. If a well is drilled in the updip waste zone of a trapped accumulation, cal ulations can be made to estimate the distance downdip to the oil-water contact.

Cored wells updip from three economic stratigraphic traps were studied to determine if they were in the waste zone of the accumulation and to test the hypothesis that calculations to determine the oil-water contact in a field can be made from shows in updip waste-zone wells. Two oil-waste zones and one gas-waste zone were studied. Results of the calculations based on available data agree closely with documented oil columns in the fields studied. These results suggest that the concept is valid and can be used both qualitatively and quantitatively as an exploration tool in exploring for oil or gas as an exploitation tool in developing fields.

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