The presence of oil in certain geologic traps and its absence in many others which at first appear favorable emphasizes the need of exhaustive studies of the controlling factors involved in the accumulation of oil. Comparison of productive and non-productive traps in areas where source beds appear alike leads toward certain deductions concerning migration of oil. These deductions must be checked against various observations and experimental evidence. Although contrary to some theories that have been widely held, it seems necessary to conclude that oil must experience a comparatively early origin and migration. Also that increasing overburden and compaction seem to be mainly responsible for migration of the oil into the reservoir. The lateral variation in thickness of over urden seems to be the main source of forces which cause and give direction to the movement of fluids within the reservoir. Provided conditions remain favorable there seems to be no need to proscribe limits as to distance of migration.

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