## 4 Results
### Microscopic Pore-Throat Structure Characteristics  
The mercury injection curve in the high-pressure mercury intrusion experiment reflects the connectivity and distribution of pores and throats. A typical mercury intrusion curve is generally divided into three sections: an initial rising section, a middle stable section, and a final upward bending section [39]. The variation range of each curve parameter is large, indicating strong heterogeneity of the Denglouku Formation tight sandstone reservoir in the study area. Based on the high-pressure mercury intrusion data of 18 representative samples from this test (Table 2), the mercury injection curve can initially show that the pore-throat distribution of the Denglouku Formation tight sandstone reservoir in the study area is relatively heterogeneous.  
Figure 2: Physical properties of Xujiaweizi Fault Depression Denglouku Formation tight sandstone: (**a**) porosity distribution frequency histogram; (**b**) permeability distribution frequency histogram; (**c**) porosity and permeability cross–plot.  
Figure 3: Pore and throat microscopic features of the Denglouku Formation reservoir in the Xujiaweizi area: (**a**) Narrow lamellar, S3, 2914.7 m; (**b**) Narrow lamellar, S1, 2889.8 m; (**c**) Dissolution pore, S13, 2725.3 m; (**d**) Intragranular dissolution pore, S12, 2695 m; (**e**) Tubular structures, S5, 3075.3 m; (**f**) Feldspar dissolution pores, S15, 3055.5 m; (**g**) Micropore, S11, 2898.6 m; (**h**) Residual intergranular pore, S2, 2860.6 m; (**i**) Microfracture, S8, 3148.4 m.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Pore–Throat** & **Pore–Throat** & **Pore–Throat** & & & **Maximum** & **Withdrawal** \\
**Sample** & **Radius** & **Radius** & **Radius** & **Softing** & **Scowness** & & **Injection Saturation/\%** & **Efficience** \\
**Number** & **Maximum** & **Average** & **Median** & **Coefficient** & & & **uration/\%** & **\%** \\  & /\(\mu\)m & /\(\mu\)m & /\(\mu\)m & & & & & **direction/\%** & **\%** \\ \hline S1 & 1.1 & 0.371 & 0.258 & 2.95 & 1.6 & 71.8  
The pore-throat size distribution in the study area was derived from the high-pressure mercury injection (HPMI) data, as shown in Figure 4. The distribution frequency of all the sample pore throats was primarily unimodal, with the main distribution range of pore throats between 0.01 \(\upmu\)m and 1 \(\upmu\)m. The pore-throat distribution varies greatly, with an average pore-throat radius distribution range of 0.9-0.013 \(\upmu\)m and an average value of 0.32 \(\upmu\)m. The median pore-throat radius distribution range was 0.004-0.538 \(\upmu\)m, with an average value of 0.12 \(\upmu\)m. According to the pore classification standard, the effective pore space types are classified as micropores (\(\leq\)10 nm), small pores (10-100 nm), mesopores (100 nm-1 \(\upmu\)m), and macropores (?1 \(\upmu\)m). The Denglouku Formation tight sandstone samples in the study area show almost no development of macropores, with mainly micropores, small pores, and mesopores developed. Through a statistical analysis of the volume fraction and porosity of pore throats with different pore diameters, it was determined that the average volume fractions of mesopores, small pores, and micropores were 16%, 51%, and 33%, respectively, with average porosities of 1.17%, 3.47%, and 1.7%.