Despite the existence of some truly giant oil and gas fields as well as numerous smaller ones in stratigraphic traps, purposeful search for such traps has been less rewarding than exploration for structural ones. Seismic exploration has been successful in mapping reefs, but definition of wedgeouts of porous clastic reservoirs is generally beyond the limits of resolution of seismic methods.

Basins with a record of tectonic instability, with important unconformities and overlaps, and with alternations of marine, paralic, and fluviatile facies are likely to contain numerous clastic stratigraphic traps. Stable but continually subsiding evaporite basins or stable shelves bordering evaporite basins or troughs where fine clastics were deposited are the chief sites for reef development. In the parts of basins where structural relief is low, most of the hydrocarbons are likely to have been trapped stratigraphically.

Systematic search for stratigraphic fields, coordinating the results of seismic surveys with detailed stratigraphic studies, followed by drilling of wells by operators who are willing to assume higher than normal dry hole risk, will continue to be the principal exploration method for finding stratigraphic oil and gas fields unless a direct method of oil finding is discovered. Contributors to this symposium have shown how improvement of the techniques of stratigraphic analysis are enabling explorationists to identify their objectives with greater precision.

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