## 5 Quantitative Analysis of Pore-Throat Network
### Quantitative Analysis of Pore  
#### 5.1.1 Pore Radius  
Figure 12 shows the distribution of pore radius in the REVs of the carbonate samples, from which positive skewness was observed for all the samples. The pore radius of carbonate was primarily in the range of 20-500 \(\upmu\)m. [PERSON] and [PERSON] [25] classified the pores of carbonate into megapores (4-256 mm), mesopores (0.0625-4 mm) and micropores (<0.0625 mm) based on the pore diameter. According to their classification, macropores are not existent in any of the REV2s of the carbonate samples. The majority of pores in the REVs are mesopores. The average radius of the pores is significantly larger for samples A and C compared to samples B, D and E.  
A comparison for the distribution of pore radius between the sandstone and the carbonate is provided in Figure 13, where a confidence interval of 95% was imposed. As shown in Figure 13, the average pore radius of carbonate was much larger than that \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Rock Sample**}} & \multicolumn{4}{c}{**Carbonate**} & \multicolumn{2}{c}{**Sandstone**} \\ \cline{2-7}  & **A** & **B** & **C** & **D** & **E** & **S** \\ \hline Number of pores & 4335 & 6001 & 1042 & 4651 & 6464 & 2708 \\ Number of throats & 4395 & 6167 & 1013 & 3889 & 5261 & 264 \\ Maximum radius of pore (\(\upmu\)m) & 1573.95 & 1698.91 & 1374.45 & 1025.14 & 783.52 & 146.39 \\ Average radius of pore (\(\upmu\)m) & 193.50 & 130.71 & 174.82 & 127.85 & 122.81 & 44.37 \\ Maximum radius of throat (\(\upmu\)m) & 1044.66 & 1501.23 & 1372.71 & 776.15 & 670.09 & 91.18 \\ Average radius of throat (\(\upmu\)m) & 127.04 & 66.25 & 114.26 & 77.11 & 64.55 & 23.57 \\ Maximum length of throat (\(\upmu\)m) & 1783.67 & 1538.80 & 1615.36 & 1678.78 & 1123.81 & 155.19 \\ Average length of throat (\(\upmu\)m) & 312.81 & 195.86 & 278.93 & 230.03 & 205.19 & 63.82 \\ Maximum pore–throat aspect ratio & 54.84 & 37.26 & 35.81 & 27.09 & 33.19 & 19.14 \\ Average pore–throat aspect ratio & 2.04 & 2.33 & 2.07 & 2.06 & 1.86 & 0.48 \\ Maximum volume of pore (\(\upmu\)m\({}^{3}\)) & 6.04 \(\times\) 10\({}^{10}\) & 1.03 \(\times\) 10\({}^{11}\) & 1.14 \(\times\) 10\({}^{11}\) & 2.32 \(\times\) 10\({}^{10}\) & 2.08 \(\times\) 10\({}^{10}\) & 1.15 \(\times\) 10\({}^{8}\) \\ Average volume of pore (\(\upmu\)m\({}^{3}\)) & 7.59 \(\times\) 10\({}^{8}\) & 1.94 \(\times\) 10\({}^{8}\) & 9.96 \(\times\) 10\({}^{8}\) & 1.70 \(\times\) 10\({}^{8}\) & 1.38 \(\times\) 10\({}^{8}\) & 3.68 \(\times\) 10\({}^{6}\) \\ Maximum volume of throat (\(\upmu\)m\({}^{3}\)) & 5.55 \(\times\) 10\({}^{9}\) & 2.24 \(\times\) 10\({}^{9}\) & 8.61 \(\times\) 10\({}^{9}\) & 1.67 \(\times\) 10\({}^{9}\) & 2.52 \(\times\) 10\({}^{9}\) & 1.36 \(\times\) 10\({}^{7}\) \\ Average volume of throat (\(\upmu\)m\({}^{3}\)) & 7.19 \(\times\) 10\({}^{7}\) & 1.79 \(\times\) 10\({}^{7}\) & 1.02 \(\times\) 10\({}^{8}\) & 2.07 \(\times\) 10\({}^{7}\) & 1.82 \(\times\) 10\({}^{7}\) & 6.94 \(\times\) 10\({}^{5}\) \\ Maximum coordination number & 28 & 48 & 23 & 27 & 29 & 3 \\ Average coordinate number & 1 & 1 & 1 & 1 & 1 & 0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistical results of pore network of REV2 of tested samples. of sandstone. Using a scanning resolution of 61.75 \(\upmu\)m for the carbonate samples, the observed minimum and maximum pore radii were 25 \(\upmu\)m and 1600 \(\upmu\)m,, respectively. Using a scanning resolution of 30.45 \(\upmu\)m for the sandstone sample, the observed minimum and maximum pore radii were 12 \(\upmu\)m and 146 \(\upmu\)m, respectively. For both types of rock, megapores did not exist in the samples. The 95% confidence interval for the pore radius of sandstone was 10-80 \(\upmu\)m (sample S), while for carbonate, it was 20-490 \(\upmu\)m (sample A), 20-270 \(\upmu\)m (sample B), 20-480 \(\upmu\)m (sample C), 20-270 \(\upmu\)m (sample D), 20-240 \(\upmu\)m (sample E), respectively. This confirms a much wider range of pore radius for the carbonate compared to the sandstone.