Deep complex oil and gas reservoirs are the future directions of oil and gas exploration. The exploration potential of Paleocene deposits in the Lufeng sag is enormous. However, due to the greater burial depth and complex oil and gas accumulation conditions of the Paleocene, few large-scale reservoirs have been discovered and the next exploration strategy is unclear. In this study, based on the Paleocene geological data of the Southern Lufeng sag, a model of hydrocarbon accumulation based on functional element control is constructed using geostatistical and numerical simulation techniques. The hydrocarbon accumulation elements, thresholds, boundaries and scopes are clarified, and the favorable zones of hydrocarbon accumulation of the lower Enping Formation are predicted using the model of hydrocarbon accumulation based on threshold combination control. The results indicate that the source rock, reservoir, caprock, and low-potential area are the four functional elements controlling hydrocarbon accumulation. Since there are three types of low-potential zones, a total of six accumulation elements are considered to control hydrocarbon accumulation, and the corresponding hydrocarbon accumulation control thresholds are determined by the model of hydrocarbon accumulation according to the controlling effects of these accumulation elements. The predicted Type I favorable zones are located in the eastern part of Lufeng 13 east sub-sag and the northern and southern parts of Lufeng 7 sub-sag; Type II favorable zones are located in the western part and around the Lufeng 13 east sub-sag; Type III favorable zones are adjacent to Type II favorable zones. The hydrocarbon shows are all located in the overlapping zone of five or more accumulation elements.

Significant breakthroughs have been achieved in the exploration of Paleogene reservoirs in the Lufeng Depression. However, as drilling depth is becoming greater, the discovered oil and gas reservoirs show signs of transition from conventional to unconventional accumulations, and the identification of conventional and unconventional reservoir boundaries is of particular significance. Herein, the hydrocarbon dynamic field boundaries in the Lufeng Depression are comprehensively identified by the geological drilling result method, the sandstone pore throat radius critical value discrimination method and the dry layer drilling rate variation method; then, the hydrocarbon dynamic field is divided and the characteristics and differences of hydrocarbon accumulations in each hydrocarbon dynamic field are compared. The results show that the buoyancy-driven hydrocarbon accumulation depth in the Lufeng Depression is between 3,500-4,000 m, and the hydrocarbon accumulation depth limit is about 5,800 m. The focus of research on Paleogene oil and gas exploration in the Lufeng Depression should be placed on conventional oil and gas reservoirs in the free dynamic field and tight oil reservoirs in the reformed dynamic field. As for the Enping Formation and Upper Wenchang Formation, efforts should concentrate on conventional oil and gas reservoir exploration, and the tight reservoir of Lower Wenchang Formation should be explored in the high fracture density area in C-4 and C-8 well blocks and the west of C-8 well block of the Lufeng 13 sag. The research results of this paper are of great value in further increasing oil and gas production and the explorarion of reservoirs in the Lufeng Depression.