关键词: 鄂尔多斯盆地, 富县地区, 长7₃亚段, 页岩油, 储集特征, 含油性

Abstract: During the deposition period of the third sub-member of the seventh member of the Triassic Yanchang Formation (Chang 7₃ sub-member), Fuxian area was located in the depo-center of the eastern lake basin, showing abundant shale oil resources and good exploration prospects. However, few studies have been conducted on shale oil reservoir characteristics, and there is a lack of the study on reservoir space characteristics and oil-bearing property, which restrict shale oil exploration and deployment practice. By using core observation, whole rock mineral XRD analysis, chloroform extraction, NMR, organic carbon abundance and porosity test data, the petrological and mineralogical characteristics, reservoir space, pore structure and oil and gas bearing property are analyzed in Fuxian area, which indicates that three rock categories are observed in Chang 7₃ sub-member, such as shale, silty-fine sandstone and tuff. Based on the development degree of lamina, the shale category is subdivided into four rock types. The main mineral composition of shale section includes quartz, feldspar, carbonate and clay minerals, as well as a small amount of pyrite. The reservoir is dominated by four types of pores, i.e., intergranular pore, intragranular pore, organic pore and microfracture. The meso-macropores are relatively developed in silty-fine sandstone, and the NMR T₂ spectrum is characterized by multi-peak and left-biased single-peak types. The micropores are relatively developed in black shale, with relatively few macropores, and the NMR T₂ spectrum is mainly multi-peak and right-biased single-peak types. The silty-fine sandstone with good oil-bearing property and high oil saturation index is the optimal shale oil reservoir in Chang 7₃ sub-member, followed by the laminated shale. The comprehensive study indicates that both silty-fine sandstone and shale targets have certain exploration potential, which are potential fields for increasing reserves and production in the future.