Shallow layer hydrocarbon accumulation characteristics and their exploration significances in Shijiutuo uplift,Bohai sea

Hydrocarbon exploration has been going on in Shijiutuo uplift for 40 years so far,which is one of the regions that have the longest exploration history in Bohai sea. After many years of no-discovery exploration activities,several large—medium fields were discovered in shallow layer in Shijiutuo uplift in recent years. In this paper the exploration process in Shijiutuo uplift was reviewed,and the characteristics of structures,oil sources,and reservoir-seal assemblages of the shallow reservoirs with the drilling were systematically analyzed,geochemical and geophysical data being considered as a whole. After then,the hydrocarbon accumulation model was summarized. The result shows that the keys to exploration breakthrough in this area are the new geological knowledges obtained from innovational ideas:(1) the coupling of low-amplitude structure setting and lithology is one of the keys to shallow hydrocarbon accumulation;(2) re-understanding the structural characteristics of Shijiutuo uplift,especially confirming the northwest-trending buried faults,plays an important role in the identification of the low-amplitude structures;(3) identifying hydrocarbon sources effectively helps to improve the success ratio of exploration. The innovational ideas and knowledges which were formed in the processes of hydrocarbon exploration in this area and were summarized in this paper can be widely referenced to in other areas of Bohai sea.