Abstract:

The accumulation mechanism and characteristics of shale oil were investigated. In comparison with shale gas, shale oil is more strict in accumulation conditions, more limited in distribution area, and more challenge in exploration. In the USA, shale oil is a kind of light oil in the marine shale and it is characterized by large distribution, high maturity, low density, low wax content and low viscosity. While in China, shale oil is a kind of heavy oil in the continental shale and it is characterized by small distribution area, low maturity, high density, high wax content and high viscosity. For the marine shale in USA, the quartz and carbonate were mostly biological sources. The quartz has a good positive correlation with the total organic carbon. It controls the oil content and is conducive to the fracturing. While for the continental shale in China, the quartz was of clastic source and the carbonate was chemical deposition. The quartz has a negative correlation with the total organic carbon and is not conducive to the fracturing. These differences may be the reasons of low shale oil production, which severely restricted the exploration and development of shale oil in China. It suggests that the shale oil exploration should focus on areas with relatively high maturity in central depressions and areas with highly developed sandstone interbed on slopes. The former features in ‘light oil, high pressure and easy fracturing’, while the latter is characterized by ‘well developed interbed and easy fracturing’.

Key words: Shale oil, Accumulation mechanism, Forming characteristics, Continental