Abstract: Secondary exploration is a new petroleum exploration idea and method for oil-rich sags. Essentially it is the reappraisal of the distribution law of undiscovered petroleum resources in oil-rich sags. The core is to cognize, evaluate and deploy on the whole. Oil-rich sags have favorable conditions for carrying out secondary exploration, which include abundant residual petroleum resources, and unbalanced exploration in different zones and domains. New exploration theories and recognitions provide theoretical guides for secondary exploration. High accuracy acquisition techniques and large area processing techniques of 3D seismic data have witnessed a rapid development and have been widely applied, providing strong technical support for secondary exploration.

Key words: oil-rich sag, secondary exploration, geological conditions, reservoir forming theories, exploration technique