Abstract: The formation conditions are favorable and hydrocarbon resources are abundant in Shuguang-Leijia area of the western sag of Liaohe Oilfield. Subtle reservoir types are mainly the buried hill reservoirs and the Palaeogene special lithologic reservoirs. Main factors controlling hydrocarbon of subtle reservoirs and their distribution rules in the area are studied systematically with the analysis of the geologic setting. The result shows that the subtle reservoirs in the area are mainly determined by such factors as the structural-depositional environment, valid source rocks, fault surface, unconformity surface and sandbody transporting layers, etc. Formation of the buried hills and special lithologic rocks are primarily controlled by structural-depositional environment. The distribution of subtle reservoirs is horizontally around generating sags. Subtle reservoirs are vertically distributed along by fault surface and unconformity surface. The distribution set of subtle reservoirs is controlled by some main source-reservoir-cap assemblages. Formation models of hydrocarbon accumulations of subtle reservoirs tend to vary in three different tectonic settings including sags and slopes as well as uplifts.

Key words: main controlling factor, distribution rule, subtle reservoir, Liaohe Depression, Shuguang-Leijia area