INVESTIGATION ON THE POOL-FORMING TIME OF THE CHENGDAO OILFIELD IN THE BOHAIWAN BASIN USING THE HYDROCARBON GENERATION KINETICS METHOD

The Chengdao oilfield of the Bohaiwan Basin is characterised by complicated petroleum infilling history. Up to now, there still remain some problems to be solved. In this paper, the multi-cool traps GC, a patented instrument from the Californian Institute of Technology, is used, combined with related Kinetics software, to investigate hydrocarbon generation kinetics parameters of 2 typical source rocks from the southern part of Bozhong Depression. Based on this, petroleum generation history of source rocks from the Chengbei Depression and Sha'nan Depression is modeled with Kinetics software. The results have shown that, the Es³ source rocks from Chengbei Depression entered into oil window about 5 Ma ago, and the present conversion of hydrocarbons C₁₃⁺ has reached 0.65. The Es³ source rocks from Sha'nan Depression have lower maturation level, with petroleum generation occurring 2 Ma ago, and the present C₁₃⁺ conversion has reached 0.24. However, the Ed² source rocks from these 2 depressions have not become mature. The Chengdao oilfield can be subdivided into 2 petroleum accumulation systems: the lower system of buried hill-lower Dongying Formation and the upper system of upper Dongying Formation-Minghuazhen Formation. Combined with petroleum geology and geochemistry of the petroleum accumulation systems, it is belived that, the lower accumulation system is mainly related to the earlier formed petroleum from the Es³ source rocks from Chengbei Depression, and petroleum in the upper accumulation system originated from the later stage petroleum generation of the Es³ source rocks from Chengbei Depression. The Es³ source rocks from Sha'nan Depression possibly have contribution to the lower accumulation system near slope area.