## 5 Discussion  
### Quantitative Characterization of Reservoir Pore Structure  
Different types of pore volume proportions can be obtained based on the pore classification (Table 4). The total pore volume of the Wufeng-Longmaxi Formation in the Z-3  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{3}{c}{**Pore Volume (10\({}^{-3}\) cm\({}^{3}\))**} & \multirow{2}{*}{**Total Pore Volume (10\({}^{-3}\) cm\({}^{3}\))**} \\ \cline{2-2} \cline{4-5}  & **Micropores** & & & \\ \hline Q0 & 4.949 & 4.502 & 0.509 & 9.96 \\ \hline Q1 & 12.520 & 4.123 & 0.070 & 16.713 \\ \hline Q2 & 5.146 & 11.370 & 1.398 & 17.914 \\ \hline Q3 & 6.572 & 6.064 & 0.483 & 13.119 \\ \hline Q4 & 8.251 & 6.867 & 0.674 & 15.792 \\ \hline Q5 & 12.084 & 10.454 & 0.875 & 23.413 \\ \hline Q6 & 9.121 & 6.791 & 0.749 & 16.661 \\ \hline Q7 & 5.287 & 6.476 & 0.404 & 12.167 \\ \hline Q8 & 16.291 & 7.145 & 1.570 & 25.006 \\ \hline Q9 & 12.865 & 3.945 & 0.857 & 17.667 \\ \hline Q10 & 9.902 & 5.427 & 0.903 & 16.232 \\ \hline Q11 & 11.176 & 2.569 & 0.651 & 14.396 \\ \hline Q12 & 17.868 & 0.731 & 0.0399 & 18.6389 \\ \hline Q13 & 13.882 & 0.481 & 0.042 & 14.405 \\ \hline Q14 & 11.993 & 2.477 & 0.679 & 15.149 \\ \hline Q15 & 16.271 & 0.694 & 0.225 & 17.19 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Pore volumes of different types of Wufeng–Longmaxi Formation shale samples in the Z-3 well.  
Figure 7: Relationship between D\({}_{1}\) and D\({}_{2}\) of the middle and upper Longmaxi Formation (layers 3, 4, 5, and 6) shale in the Z-3 well.  
well varies from 9.96 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) to 25.006 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) at different depths, with an average value of 15.5543 \(\times\) 10\({}^{-3}\) cm\({}^{3}\). The volume of macropores ranges from 0.0399 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) to 1.570 \(\times\) 10\({}^{-3}\) cm\({}^{3}\), with an average value of 0.6331 \(\times\) 10\({}^{-3}\) cm\({}^{3}\), accounting for 0.21% to 7.8% of the total volume and an average proportion of 3.77%. The volume of mesopores ranges from 0.481 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) to 11.370 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) (avg. 5.007 \(\times\) 10\({}^{-3}\) cm\({}^{3}\)), which accounted for 3.34% to 63.47% of the total pore volume, with an average percentage of 30.72%. The volume of micropores varies from 4.949 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) to 17.868 \(\times\) 10\({}^{-3}\) cm\({}^{3}\) (avg. 65.51%), with an average proportion of 65.51% and a range from 28.72% to 96.37%.  
Therefore, the pore volume of the Wufeng-Longmaxi Formation in the Z-3 well is mainly comprised of micropores and mesopores, dominated by micropores, which verifies the analysis of the characteristics of the pore size distribution curves. The analysis shown in Figure 8 reveals that the proportion of micropore volume displays moderately negative correlations with the burial depth, while the proportion of mesopore volume exhibits moderately positive correlations with depth.  
As shown in Figure 9, the mesopore volume exhibited a weak positive linear relationship to TOC content and no obvious relationship to quartz content. The TOC content is indicative of the richness of organic matter. Hence, mesopores of the Wufeng-Longmaxi Formation shales mainly consist of organic matter pores.