The Pearl River Mouth Basin (PRMB) covers an area of approximately 20×10 4 km 2. However, oil-gas fields detected in this area thus far are highly concentrated and controlled predominantly by second-order structural belts, the seven largest of which aggregate proved oil reserves of 7.7×10 8 m 3 , accounting for 86% of the total discovered reserve in the basin. These second-order structures have one common phenomenon: oil is contained in all traps present in them. In other words, they are all belt-wide petroliferous reservoirs. Research has identified eight types of second-order structural belts under two categories in the eastern PRMB. Their petroliferous properties are subject to three typical constraints: petroliferous properties of subsags hosting these structural belts, locations of these belts in the petroleum system, and availability of traps prior to the hydrocarbon expulsion and migration. The formation and distribution of oil reservoirs in these belts are characterized by subsag-belt integration and "three-in-one". The former indicates that sags and the second-order structural belts within the supply range of the sags constitute the basic units of hydrocarbon accumulations and are therefore inseparable. The latter indicates that a belt-wide petroliferous second-order structural belt always contains three important elements: hydrocarbon richness, effective pathway and pre-existing traps.

The Pearl River Mouth Basin is the largest petroliferous basin in the northern South China Sea, where hydrocarbon accumulation is strongly controlled by fault activities. This study performed the quantitative evaluation of the effects of faults on hydrocarbon migration and accumulation in the basin. The results indicate that the critical values of vertical migration of middle-shallow hydrocarbon, including the active strength of faults and the ratio of fault throw to shale caprock thickness, were up to 10 m/Ma and 5, respectively. The lateral hydrocarbon migration efficiency of the unbreached relay zone was higher than that of the barely breached and strongly breached types. The lower critical value of shale gouge ratio for the clay sealing efficiency was 0.32. Additionally, the zones with the EWtrending transtensional faults were found to have unique dual functions of migration and stress sealing, suggesting that the linking fault positions play important roles in the lateral migration of hydrocarbons. Finally, seven hydrocarbon accumulation models controlled by faults in different tectonic settings were constructed to clarify the effects of faults on the vertical and lateral migrations of hydrocarbon. These models suggested that fine hydrocarbon exploration should be undertaken in the northeastern Baiyun Sag, and that middle-deep hydrocarbon exploration should be enhanced in the Enping, Huizhou, and southwestern Baiyun Sags.