Abstract: Based on the research on physical properties and the distribution characteristics of crude oil in Santanghu basin, combining the geological condition, the authors analyze the influencial factors of the physical properties of crude oil. It is shown that physical characteristics of crude oil depend not only on group compositions, but also on maturity, burial depth, preservation condition and compositional gravity differentiation. The factors of influence on density include content of saturation hydrocarbon, arocomatic hydrocarbon, resin, asphaltene and wax. Viscosity mainly depends on content of saturation hydrocarbon, arocomatic hydrocarbon and resin, not on asphltene and wax. For the change of physical properties of the crude oil in Lucaogou Formation, Niujuanhu oil field, the bigger its depth is, the higher its viscosity, which are different from other area and stratum, and it is the result of gravity differentiation of different hydrocarbons. The physical properties variation of crude oil in other area decrease as its depth increasing, mainly related to preservation condition, water leaching and oxidation, the recognition is of an importance to other areas in the research on physical property distribution characyeristics of crude oil.

Key words: density of crude oil, viscosity of crude oil, gravity differentiation, maturity of crude oil, Santanghu Basin