## 4 Results
### Pore Systems
#### 4.3.2 Quantitative Analysis  
By processing and analyzing SEM images of 62 samples via ImageJ, the pore structure types were categorized into six classes. The specific statistical results of the pore structure parameters for individual samples are shown in Figure 6.  
The turbidite reservoirs exhibit three types of pore-throat combinations: coarse pore-coarse throat (Type A), medium pore-medium throat (Type B), and fine pore-medium throat (Type C). These types show significant differences in their average porosity, range of  
Figure 6: Pore–throat combination types, pore size analysis, and pore type proportion in different sedimentary systems in Es\({}_{3}\) in Linnan Subsag. -pore diameter variations, and proportion of pore area for different types. The Type A pore structure has a high average porosity of 6.68%. The range of pore diameters varies greatly, with a minimum of 1.92 \(\upmu\)m and a maximum of 25.37 \(\upmu\)m. For Type B and Type C pore structures, the average porosity and pore diameter decrease sequentially, and the range of pore diameters is smaller than that of Type A. Type B reservoirs have an average porosity of 4.41% and pore diameters ranging from 0.46 \(\upmu\)m to 14.14 \(\upmu\)m. The Type C reservoirs present an average porosity of 2.12% and pore diameters ranging from 0.35 \(\upmu\)m to 9.52 \(\upmu\)m. All three types of turbidite sediment pore-throat combinations predominantly feature intergranular residual pore areas (exceeding 80%), with Type A accounting for nearly 10% of the dissolution pore area. The Type B pore areas are predominantly intergranular residual pores, whereas Type C pores represent relatively larger proportions of intergranular micropores and microcrack areas. In delta front sediment deposits, three types of pore-throat combinations have also been developed: medium pore-coarse throats (Type D), medium pore-fine throats (Type E), and fine pore-fine throats (Type F). The average porosity and range of pore diameter variations for Types D, E, and F are significantly smaller than those for Types A, B, and C in turbidite reservoirs. The average porosities of Types D, E, and F decrease, with values of 1.99%, 1.68%, and 0.86%, respectively. However, Type E, the medium pore-fine throat type, has the largest range of pore diameters from 0.45 \(\upmu\)m to 6.52 \(\upmu\)m, whereas Type F has the smallest minimum diameter at only 0.12 \(\upmu\)m. The proportion of the pore area varies greatly among different pore-throat combinations in delta front sedimentary reservoirs. Type D is primarily composed of intergranular dissolution pores and residual intergranular pores, accounting for approximately 80%, with slightly more intergranular dissolution pores. Type E predominantly consists of residual intergranular pores (70.60%), followed by intragranular dissolution pores (11.63%). Type F has the highest proportion of residual intergranular pores, accounting for 64.88% of the pore area. The second highest proportion is intergranular micropores at 22.18%, which is significantly greater than that of the other pore-throat combination types. The sizes of the pores in tight sandstone reservoirs with different pore-throat structures vary significantly. Type A primarily consists of pores with diameters ranging from 4 \(\upmu\)m to 8 \(\upmu\)m, with more than 10% of the pores having diameters exceeding 20 \(\upmu\)m. The Type B and D reservoirs predominantly have pores with diameters larger than 2.5 \(\upmu\)m. In Type B, the proportion of pores with diameters between 1.0 \(\upmu\)m and 2.5 \(\upmu\)m decreases as the diameter increases. Conversely, in Type D, the proportion of pores across all size ranges increases with the increasing diameter. The Type C and F reservoirs feature pores with diameters ranging from 0.5 \(\upmu\)m to 1.0 \(\upmu\)m, accounting for more than 35% of the total.