The primary factor impacting the tight sandstone reservoirs and fluid flow capacity represents the pore-throat structure. On the basis of petrophysical characteristics test, scanning electron microscopy (SEM), and casting thin-section examination of tight sandstone reservoir specimens from the Permian Lucaogou Formation in Jimsar Sag, Junggar Basin., the full-size pore-throat parameters and distribution characteristics were determined by constant-rate mercury injection (CRMI) analysis. Using fractal theory and multifractal theory, the pore architectures of sandstone pores are analyzed. Mercury intrusion capillary pressure (MICP) is used to compute the dimensions of fractals using various fractal models and multifractal characteristics. Analysis is done on the relationships between tight sandstone pore architectures and fractal and multifractal characteristics. According to the research, a network of tightly packed sandstone pores may be assessed using the dimensions of fractals computed from a 3D capillary model. When displacement pressure is increased, the dimensions of fractals rise; when permeability, pore-throat diameter, and variable coefficient are increased, it falls. Tight sandstone pores exhibit multifractal features, according to the multifractal analysis, and multifractal parameters may depict the size, concentration, and asymmetry of the pore size distribution (PSD). Sandstone’s PSD is comparable when its multifractal parameters (Δα, Δ f , α 0 , α 1 , α 2 ) are identical. Pore diameters of tight sandstone are positively connected with information dimensions D 1 and correlation dimensions D 2 , and information dimensions D 1 have a greater impact on PSD than correlation dimensions D 2 . Additionally, the 3D capillary model’s dimensions of fractals and D 1 exhibit a substantial negative association. These findings play a significant guiding role in the quantitative characterization of unconventional reservoir pore structures. The multifractal technique is effective to define the heterogeneity of the sandstone pore system and to differentiate between distinct PSD in heterogeneity.

The Triassic Jiucaiyuan Formation is a vital oil and gas exploration target in the eastern part of the Junggar Basin. In this work, cores, thin sections, particle sizes, and conventional physical properties were analyzed in order to understand the sedimentary characteristics and depositional model of the Jiucaiyuan Formation in the Beisantai Uplift and to clarify the factors controlling reservoir development. The results demonstrate that the Jiucaiyuan Formation can be divided into seven lithofacies, namely massive bedding gravel, massive bedding sandstone, trough bedding sandstone, plane bedding sandstone, wavy bedding sandstone, parallel bedding siltstone, and massive bedding mudstone. Braided river delta facies dominate the Jiucaiyuan Formation. Nine main subtypes of facies were observed: flood plain, braided channel above lake level, natural levees above lake level, braided channel under lake level, interdistributary bays, natural levees under lake level, mouth bars, prodelta mud, and beach bar. The braided channel under lake level, mouth bar, and beach bar reservoirs exhibited the best physical properties, with average porosities of 16.54%, 19.83%, and 20.41%, respectively, and average permeabilities of 3.43 mD, 9.91 mD, and 12.98 mD, respectively. The physical properties of reservoirs in the study area are mainly controlled by sedimentation. Braided channels under lake level, mouth bars, and beach bars are favorable facies for the development of high-quality reservoirs. The results of this study are expected to serve as a theoretical basis for further exploration and development of oil and gas in the study area.