## 4 Results
### Fractal Dimension Features  
Fractal dimension is calculated from the capillary pressure and mercury saturation data obtained via HPMI experiments, employing Equations (3) and (4). Typical fractal characteristics are shown in Figure 9, where there is a significant linear correlation between  
Figure 8: Typical NMR pore diameter incremental and cumulative curves for tight sandstones. (**A**) Turbidite sandstone. Figures (**a–c**) correspond to the three types of pore structure A, B, and C, respectively. (**B**) Delta front sandstone. Figures (**d–f**) correspond to the three types of pore structure D, E, and F respectively. Notes: (**a**) Sample TX307-1, 4230.6 m. Sample TX307-2, 4227.1 m. (**b**) Sample T305-1, 4032.07 m. Sample T305-2, 4057.02 m. (**c**) Sample L86, 3935.58 m. (**d**) Sample T306-3, 4005.04 m. (**e**) Sample T305-3, 4215.8 m. Sample T306-1, 4017.33 m. Sample T306-2, 4004.3 m. Sample TX307-3, 4364.7 m. Sample L81, 3899.41 m. (**f**) Sample L98-1, 4294.58 m. Sample L98-2, 4297.21 m.  
the wetting phase saturation and the capillary pressure on a double logarithmic coordinate, with the fractal dimension correlation R\({}^{2}\) for each segment exceeding 0.9. The pore characteristics of the two sets of sedimentary reservoirs exhibit different fractal features, but overall, they present a multisegment fractal pattern (Table 1 for specific data). The numerical values and differences of multi-segment fractal dimensions can quantitatively characterize pore structure heterogeneity across different pore size scales,  
Figure 9: Fractal dimension features of pore structure for tight sandstone samples of different sedimentary systems. Notes: (**a**) Turbidite sandstone. (**b**) Turbidite sandstone, Type A, Sample TX307-1. (**c**) Turbidite sandstone, Type B, Sample T305-2. (**d**) Turbidite sandstone, Type C, Sample L86. (**e**) Delta front sandstone. (**f**) Delta front sandstone, Type D, Sample T306-3. (**g**) Delta front sandstone, Type E, Sample T306-1. (**h**) Delta front sandstone, Type F, Sample L98-1. with each fractal segment corresponding to a specific pore size range and geological genesis. The macropore segment (D\({}_{1}\)) corresponds to primary macropores and macroscopic fractures with pore diameters greater than 100 nm, which can reflect the complexity of the fracture network and flow connectivity. These features principally arise from coarse-grained intergranular pores formed during depositional grain packing and the fracture networks generated by subsequent tectonic stress. In the mesopore segment (D\({}_{2}\)), the physical pore scale is 10-100 nm, mainly revealing the modification of the pore network by compaction, cementation, and dissolution during the diagenetic processes. The microporous segments (D\({}_{3}\)) focus on the intercrystalline pores and microscopic secondary dissolution pores, which are physical pore scales less than approximately 10 nm, affecting the adsorption characteristics and specific surface area of the reservoirs [58; 59; 60]. Among the turbidite sandstone samples, Type A and B pore-throat combinations, including sample TX307-1, present two-segment fractal features (D\({}_{1}\) and D\({}_{2}\)), whereas Type C displays three-segment fractal features (D\({}_{1}\), D\({}_{2}\), and D\({}_{3}\)). Moreover, Type D, represented by sample T306-3, and Type F, represented by sample L98-1, both exhibit a two-segment fractal feature (D\({}_{1}\), D\({}_{2}\)). In contrast, Type E pore-throat combinations, exemplified by sample T306-1, correspond to a three-segment fractal feature (D\({}_{1}\), D\({}_{2}\), D\({}_{3}\)) (Figure 9). 1. Two-segment fractal characteristics: These characteristics correspond to the Type A and B pore-throat combinations in turbidite sandstones (Figure 9b,c) and the Type D and F types in delta front sandstones (Figure 9f,h). As shown in Table 1, in turbidite reservoirs, the fractal dimension D\({}_{1}\) for relatively coarse pores ranges from 2.995 to 2.998, with an average value of 2.997.