Abstract: In the past few years, new discoveries (Zhangjiaduo and Qu1 Block oil pools etc.) have been continuously obtained in exploring the Fu3 Member of the Qutang sub-sag in Haian sag, Subei Basin. which further presents favorable exploration prospect within this formation. By dissecting typical oil pools and analyzing hydrocarbon distribution features in the Fu3 Member of the Haian sag, it is realized that hydrocarbon accumulation in the Fu3 Member is mainly controlled by fine tectonic background, source-reservoir-caprock assemblage and abnormal pressure. Further studies indicate that:(1) the evolution difference of source rocks is crucial for hydrocarbon enrichment difference of the Fu3 Member in various sub-sags; (2)the oil-source faults with continuous long-term activities played important role for hydrocarbon accumulation in the Fu3 Member; (3) reasonable configuration between sand body distribution and geologic structure space was favorable for forming subtle traps (such as fault-lithology and sand updippinchout traps) in southern sub-sags. Based on the above, it has concluded that except for the Qutang sub-sag, the Fu3 Member in the regions near the Sunjiawa sub-sag, Fengbei sub-sag and Fuan sub-sag in the north have relatively favorable hydrocarbon accumulation conditions, and the major exploration target is tectonic oil pools; the Xinjie sub-sag and Haibei sub-sag in the south have lower sand ratios, being favorable regions for exploring lithological oil pools.

Key words: Haian sag, Fu3 Member, hydrocarbon accumulation, major controlling factor