Hydrocarbon dynamic field division and its relevance to oil and gas exploration for Paleogene reservoir in Lufeng Depression

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.