Abstract: Most of the oil found up to now belong to light oil bed in Beier depression of Hailaer Basin. The fresh light oil-bearing core sections of sandstones show light colour, strong odour, yellowish fluorescence. But the colour, odour and fluorescence will lost after exposed sometimes. The density range of light oil is 0.79-0.82 g/cm³. The range of viscosity is 1.60-5.40 mPa·s. Max value of total hydrocarbon is more than 0.50%, and the ratio is more than 3.0. Total pyrolysis hydrocarbon is more than 2.00 mg/g. The ratio of lighter hydrocarbon to heavier hydrocarbon is from 2 to 6. Gas chromatography of light oil shows the range of carbon number is from nC₈ to nC₂₅ and the main peak carbon is nC₁₈-nC₂₀. The chromatography changes into line after oil exposed sometimes. Oil bed, oil-water bed and water bed were identified by using crossplot of specific oil content versus effective porosity. Standard and crossplot of oil type differentiation were formed base on regression analysis among index of PS, density and viscosity. The light oil bed and heavy oil bed were differentiated according to this standard. High productivity oil bed, industry oil bed, low production oil bed and dry bed were identified according to static productivity index and dynamic productivity index. The prediction accuracy was more than 90% with this method.

Key words: Hailaer Basin, Beier depression, light oil bed, Nantun Formation