Sub-sag sorting and petroleum distribution in Beibuwan Basin

The Beibuwan Basin is a typical rift basin.It is divided into 15 sub-sags of 3 types (presenile,inhe-rited and late-formed).These 15 sub-sags are evaluated as 4 grades.The inherited sub-sags are most favorable for source rock generation and distribution.The discovered reservoirs are mainly located around petroliferous sub-sags which are controlled by the inherited sub-sags.Faults control the type and vertical distribution of reservoirs which are mainly sealed by faults and distribute along main faults.A complex hydrocarbon accumulation model,which is superimposed vertically and distributed along faults horizontally,is developed along inherited long-term active faults.In the presenile sub-sags,petroleum mainly accumulates in the 3rd member of the Liushagang Formation and is sealed by antithetic faults.