Carrying bed system feature and its controlling on oil & gas distribution in Chengbei fault step belt of Qikou sag

Controlled by tectonization and sedimentation,the Chengbei fault step belt of Qikou sag,Huanghua Depression,develops various kinds of carrying beds,including faults,sand bodies and unconformities,which formed the complex solid network pathways.The oil reservoirs whose hydrocarbon migrated vertically along the faults often have multiple oil beds overlapped around the faults.However,the oil reservoirs whose hydrocarbon migrated mainly along the connected sand bodies mainly formed in strata near by the source rocks.Hydrocarbon through the unconformity can migrate in a long distance and formed stratigraphic reservoirs.All reservoirs in the Chengbei fault step belt were formed by migration in two or more carrying beds.The multi-match relation between fault systems,sand bodies and unconformities in time and space controlled the types and distribution of reservoirs.The margin and the end of carrying bed systems are usually the significant target areas of oil and gas migration.