Abstract: For the purpose of petroleum investigation and development in Puwei Sag,Dongpu depression,the condition characteristics of hydrocarbon gathering of the Mid-sha-3 member,Shahejie formation,Eogene in Puwei sag have been studied.On the studying basis of depositional facies belt and sandstone body distribution,the favorable block for oil and gas to accumulate is predicted.The thick sand body distributions developed well lay a sound foundation for favourable sandstone reservoir in Puwei sag,Dongpu depression which provided a good base for hydrocarbon gathering.Through the study of structure,comprehensive analysis of core drilling and logging,we find many favorable conditions for hydrocarbon gathering in Puwei sag.The widespread mature hydrocarbon source rocks are the important base for hydrocarbon gathering,and the spread of different types of sand bodies provide an important reservoir space.Multiple sets of salt sedimentary cover formed a good distribution,the various genetic types of traps are the main reservoir gathering place.Evaluation has been carried out for sand-bearing beds from the Mid-sha-3 member.The results show that the best is the 4 sand-bearing bed and the most favorable block is in the middle and northwest of the west sag.