Abstract: Through more than 20 years' exploration, a variety of hydrocarbon reservoirs were discovered in Beir sag, Hailar Basin, including the structural hydrocarbon reservoir, the structural-lithologic reservoir, the structural-stratigraphic reservoir, and the buried-hill reservoir. Vertically, oil and gas are mainly distributed in buried hill in basement, Tongbomiao Formation and Nantun Formation, and small amount of hydrocarbon indication was seen in the strata of Damoguaihe Formation. Horizontally, oil and gas are mainly distributed in the hydrocarbon-generating secondary sag, and its surrounding fault zone and buried-hill zone, as well as the lithologic sand body near it. Formation and distribution of hydrocarbon reservoirs in the sag are mainly determined by hydrocarbon-generating secondary sag, the fault zone, unconformity and sedimentary facies.

Key words: Beir sag, hydrocarbon-bearing combination, type of hydrocarbon reservoir, hydrocarbon distribution