Subei basin is composed of small half grabens and features in closely-spaced faults

small traps

and homogeneous hydrocarbon abundance.Hydrocarbon pooling in Subei basin has the following characteristics:(1)The Late Eocene is the pooling period;(2)Hydrocarbon expulsion of source rocks is unilateral;(3)The migration and accumulation styles are different in the Eocene fault depression and the Palaeocene depression.The Eocene fault depression has small and isolated sandbodies

where hydrocarbons accumulate through vertical migration along the faults

the pools are distributed in the deep depression and occur vertically in multiple layers along the faults

and are dominated by structural-lithologic reservoirs.While the depression develops large delta sandbodies

hydrocarbon generation and accumulation occurring in the same layer and hydrocarbon migration is active.The pools mainly occur in the slope and uplift zones and are dominated by structural reservoirs.(4)Hydrocarbon enrichment is mainly controlled by source rock maturity

physical properties of sandbodies and sealing of the faults.The upper source-reservoir-cap rock combination is controlled by hydrocarbon migration

and the middle and lower combinations are controlled by the development of carrier beds and traps.To deal with the exploration of small complex fault block reservoirs

a set of technologies concerning seismic acquisition

processing

and interpretation

have been developed and improved.