Shenzhen Branch of CNOOC Ltd., Shenzhen 518000, Guangdong, China 

 The exploration of Lufeng 15 and Lufeng 22 sags in Lufeng depressions of Pearl River Mouth Basin is preliminary, and the understanding of sedimentary system of Wenchang Formation is relatively poor. In order to promote the exploration process of the sags, the source to sink system and sedimentary evolution of the Wenchang Formation in the sags were studied based on seismic, drilling, rock and ore analysis and other data. Six primary river systems and twenty?three secondary watershed units are recognized on steep slope, gentle slope and axial di? rection. During the Wenchang Formation deposited, the lake level changed from shallow to deep and then to shal? low, and the provenance input in the early and late stages of rifting was the strongest. The provenance of Lufeng 15 sag in the early stage mainly comes from the axial direction and gentle slope, shrinks in the middle stage, and ad? vances as a whole in the late stage. The provenance of Lufeng 22 sag is mainly from gentle slope and steep slope in the early stage, shrinking in the middle stage, and from axial direction in the late stage. Braided river delta lacus? trine sediments were developed for the Wenchang Formation. The 4 th Member of Wenchang Formation belongs to la? custrine source rock, while the 3 rd and 5 th members of Wenchang Formation form braided river delta sandstone res? ervoirs. The 5 th Member of Wenchang Formation was predicted to be a favorable exploration layer series.