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Many geological concepts of widespread application to petroleum exploration were either first, or early, observed and studied in the Mid-Continent region. Five are selected for discussion. These are: (1) pools reservoired in sandstone patches, lenses, channels and bars; (2) unconformities, truncations, and layers of geology--their influence on exploration; (3) tilted oil-water contacts, fluid pressure gradients; (4) changing structure with depth, converging strata, "bald-headed" structures, closed structures below terraces, and the hinge-line concept; and (5) one discovery leads to another--and another. These are typical of some of the simple geological phenomena that abound in this region, that seem to control much petroleum occurrence, and that are continually being used in the worl -wide search for oil and gas.

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