摘要：The fractal dimension is a parameter that de-scribes the microscopic pore-throat structure of the reservoir based on the space fractal theory.It can be used to reflect the complexity of the pore structure and predict the permeability of the reservoir. In this paper, a systematic fractal study of tight oil reser-voirs in the Chang 4+5 Member of Yanchang For-mation in the central area of Ordos Basin is con-ducted based on high-pressure mercury intrusion ex-periments. The results show that the pore structures of tight sandstone reservoirs have single fractal and multisegment fractal characteristics. Single fractal means that the full aperture has the same fractal char-acteristics. Multisegment fractal means that pores of different sizes have different fractal characteristics. The pore structure of pores with an average throat radius greater than 0.1 um is more complex and the fractal dimension is larger. This is because the disso-lution is stronger in the large pores, while the size of the small pores is more consistent, so the pore struc-ture of the large pores is more complex. Based on fractal theory, it can be found that rock permeability is a function of porosity,pore throat fractal dimen-sion Dr,capillary tortuosity fractal dimension D, and maximum pore throat radius. The permeability cal-culation model based on fractal theory can be used for high-precision quantitative characterization of reservoir permeability.
