The migrate d oil and gas from the Bonan Sag accumulating in the Sanhecun Sag of Bonan Depression of Bohai Bay Basin was studied using fluid inclusion and biomarker compound analyses, combined with the burial history modelling of typical wells and the evolution history of boundary faults. A new understanding was proposed from two aspects including oil and gas accumulation time and migration path evolution. Three hydrocarbon accu?mulation processes occurred in the Sanhecun Sag during the early Dongying, Guantao and late Minghuazhen periods according to fluid inclusion homogenization temperatures and biomarkers which reflect maturity.The early oil and gas mainly derived from the upper part of the fourth member of Shahejie Formation, and then from the third and first members of Shahejie Formation in the Bonan Sag, forming a complete hydrocarbon accumulation sequence in the Sanhecun area. During the accumulation period of Dongying Formation, boundary faults failed to stagger delta sand body. As a result, the Bonan oil and gas directly migrated along the contiguous sand and accu?mulated in Sanhecun area. Faults, sand bodies and unconformities provided a good migration channel for late oil and gas migration.It is confirmed that oil and gas migrated through"the early unified sand body" and"fault?sand body?unconformity composite" to Sanhecun Sag and the southern slope and then accumulated, forming a variety of oil and gas accumulation types.%为了解释渤海湾盆地渤南洼陷外源油气在三合村洼陷内部聚集成藏的问题,利用流体包裹体、生物标志化合物等资料,结合典型井埋藏史与边界断裂演化史分析,从油气成藏期与运移路径演化2个方面进行研究.结果发现,流体包裹体均一温度与反映成熟度的生物标志化合物参数均证实,三合村洼陷存在东营组沉积早期、馆陶组及明化镇组沉积晚期油气成藏过程,早期油气主要源自渤南洼陷沙四上烃源岩,之后渤南洼陷沙三段及沙一段烃源岩相继成熟供烃,构成了三合村洼陷完整的成藏序列.东营组成藏期,边界断层未能错开三角洲砂体,渤南油气可沿统一砂体直接向三合村运聚;晚期由断层、砂体及不整合构成的复合体系,为油气聚集提供了良好的输导通道.油气正是通过"早期统一砂体运移"和"断层—砂体—不整合复合运移"等方式向三合村洼陷内部及其南部斜坡运聚,形成多种类型的油气聚集.
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