The evolution of an exploration philosophy in the Rocky Mountain area can be reviewed in terms of the new areas involved in each successive wave of exploratory vigor. Such an analysis indicates an exploration history which comprises five episodes, each dominated by a set of guiding principles, controlled by the available data and tolls, and governed by the economics of the times: (1) discoveries related to seeps and other near-surface indications; (2) the location of major surface structures and the establishment of production in the majority of Rocky Mountain provinces; (3) detailed surface mapping, leading to the discovery of further anticlinal accumulations; (4) widespread application of geophysical tools, coupled with deeper drilling on known features; (5) geophysical and subsurface geology applied to the refinement of deeply buried structures and structural-stratigraphic traps. Signs of the emergence of a new era can be seen.

During each of these episodes certain areas and certain parts of the stratigraphic section were condemned without trial; some for economic reasons which no longer pertain, others on the basis of a variety of geologic concepts developed to satisfy a local situation and then applied broadly as sweeping generalizations. Examination of the complex tectonic and depositional history of the Rocky Mountain area suggests that at least six successive and different patterns have been impressed upon the structural and stratigraphic record. In terms of oil accumulation each pattern may be shown to have its own internal constitution, governed by tectonics, environment, and sediment-source, and an independent set of potential truncation and permeability traps related to post-depositional events. No ondemning generalization arrived at through experience with one of these varying patterns may safely be applied to the others and no area may be considered non-productive until the inherent possibilities of each pattern represented are tested.

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It may be shown that every major oil accumulation in the area is related to a combination of structural and stratigraphic conditions with increasing evidence to indicate that stratigraphic controls are dominant. Many of the stratigraphic factors can be analyzed through study of the rocks themselves and by interpretation of their geophysical responses. With the abundant outcrops of the Rocky Mountain area, the increasing availability of subsurface data, and the developing know-how whereby these data may be related to oil occurrence, there remains a broad and encouraging field for an expanding exploration program.

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