Abstract: Dawanqi Oilfield is a light oil-based oilfield. The concentration of biomarkers and the abundance of neutral nitrogenous compounds are comparatively low that make it difficult to reveal the crude oil migration characteristics. Research shows that, commonly, there is a kind of compounds with high thermal stability in oils of Dawanqi Oilfield. They are the diamondoids, including diamondoid and bidiamondoid hydrocarbons. Chromatographic analysis indicates the compounds with different structure have great discrepancy in their chromatographic retention behavior. According to the similarity of chromatographic retention behavior and stratum chromatographic effect in principle, the oil fractionation effects of Dawanqi Oilfield during migration have been studied by using the ratios of diamondoids with different chemical structure. The results show that the migration parameters based on diamondoids have obvious distribution law. In general, the migration parameters of diamondoids increase as the buried depth gets shallower. The results indicate that crude oil migrates vertically. The migration parameters of diamondoids are low in areas near deep faults. The migration parameters of diamondoid increase from south to north far from those deep faults in the plane. All these show that the main migration direction of the crude oil in Dawanqi Oilfield is from south to north.

Key words: Tarim Basin, Dawanqi Oilfield, diamondoids, migration parameter, fractionation effect