Fault characteristics and hydrocarbon accumulation in the southern Lufeng Sag, Pearl River Mouth Basin

The Lufeng Sag is a hydrocarbon-rich sag located in Zhu I depression of the Pearl River Mouth Basin, and the Paleocene in the southern sag has good exploration potential. Based on the 3D seismic data interpretation and drilling data, we analyzed the characteristics of fault deformation and evolution in the southern Lufeng Sag, and the controls of faults on hydrocarbon transport and accumulation. In addition, the types of hydrocarbon combinations were classified. Three half-grabens in the southern Lufeng Sag were controlled by three listric boundary faults with strong activity. The faults were mainly developed during the Paleogene. The distribution density of faults is the highest in the slope zones, and the dominant trends changes from NEE to nearly SN upwards. Also, the dense zone of faults migrates from east to west. The faults can be divided into hierarchical classes 1 to 3, Class 1 the formation of sags, Class 2 determines local structural belts, and Class 3 restrains structural traps. The faults in the southern Lufeng Sag were active during the deposition periods of the Wenchang Formation, the Enping Formation, and the Wenchang-Enping Formations. The faults control the formation of fault noses, fault blocks, and fault anticlinal traps, and the difference in combination models of faults and source rocks affects the efficiency of hydrocarbon migration and accumulation. Based on the hydrocarbon accumulation factors such as enrichment strata, transportation models, fault activity, and source-faults combination types, four hydrocarbon accumulation models were established: in-source autogenous self-storage, in-source autogenous up-storage, out-source side-storage and out-source down-storage This study provided a theoretical support for further oil and gas exploration in the southern Lufeng Sag.