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This paper investigates the origin and migration characteristics of petroleum in the northeastern part of the Baiyun Depression, Pearl River Mouth Basin (PRMB). The discovered petroleum in the study area is mainly located in the Lower Zhujiang Member (N1z2) and mainly originated from the Enping Formation source rocks in the eastern sag. Active faults (vertical migration) and N1z2 sandstones (lateral migration) acted as the petroleum migration systems. The fault activities in the Dongsha event controlled the episodic petroleum migration. Fractures in the fault zones provided effective conduits, and overpressure was the driving force. The vertical migration could not cross the fault zones laterally. The petroleum injection areas in the carrier beds were the contact zones of petroleum-migration faults and carrier beds. The lateral migration was steady-state migration, and buoyancy was the driving force. The migration pathways in the carrier beds were controlled by the structural morphology. Secondary petroleum migration in the study area could be divided into two parts: vertical migration along the fractures in the fault zones and lateral migration through preferential petroleum migration pathways (PPMPs) in the carrier beds. The petroleum migration behaviors, including migrating direction, driving force, and migration pattern, in the faults and sandstone carrier beds were quite different. This study provides a typical example for comprehending secondary migration processes and has great importance for determining future exploration targets in the deep-water area of the PRMB.