Abstract: After multi-stage transformation of tectonic movement, the superimposed basins in southern North China have been explored for many years, but no major progress has been made. In view of this, the main causes are discussed through the review and retrospection of the exploration history of the two major sags-Jiyuan and Tanzhuang-Shenqiu, and the careful analysis of the conditions for hydrocarbon accumulation. It is considered that the primary causes are the lack of understanding of the complex structures generated from multi-stage structure and block activities and the complex geological factors of the Upper Paleozoic and Mesozoic hydrocarbon source beds including multi-stage hydrocarbon generation and multi-stage migration and accumulation, preservation, while the secondary causes are that the new techniques and methods have not been widely used. It reveals that new geological theories and evaluating methods are required to be applied to the exploration of superimposed basins, so as to recognize the complicated geological factors and to be successful through meticulous planning and strict construction.

Key words: southern North China superimposed basin, Jiyuan sag, Tanzhuang-Shenqiu sag, condition for hydrocarbon accumulation; exploration history, considerations