Abstract:

Chezhen sag is a continental faulted basin developed in Mesozoic and Cenozoic which is located in the northwest of Jiyang depression. 3 series of source rocks such as Es₄, Es₃ and Es₁ of Lower Tertiary were well developed in this area. Featured by multiple hydrocarbon generations and composite oil-gas accumulations, multi-petroleum systems of one source corresponding to multiple reservoirs or one reservoir corresponding to multiple sources is formed in Chezhen sag. According to the results of oil and source rock correlation, multi-petroleum systems in Chezhen sag can be classified into Es₄ petroleum system, Es₃ petroleum system, and Es₁ petroleum system. Reservoir types of Es₄ and Es₁ petroleum systems are self-generation and selfstorage reservoirs, while that of Es₃ petroleum systems is self-generation and self-storage reservoir, new-generation and oldstorage reservoir, old-generation and new-storage reservoir. Three petroleum systems are characterized by the domination of different strata and superposition of petroleum system formed in different periods. Chexi subsag and Dawangbei subsag are superposition areas, where hydrocarbon is very abundant. Es₃ petroleum system is the most important petroleum system, and it is also an exploration orientation in Chezhen sag.

Key words: Chezhen sag, petroleum system, oil and source rock correlation, oil-gas reservoir, exploration orientation