# Quantitative Characterization of Micro-Scale Pore-Throat Heterogeneity in Tight Sandstone Reservoir
## 3 Discussions
### Effects of Pore Throat Heterogeneity on Reservoir Physical Properties and Fluid Mobility  
By analyzing the relationship between physical properties (porosity, permeability) and pore uniformity, throat uniformity, and combined pore-throat uniformity of different pore-throat combination reservoirs (Figure 2), it can be found that the relationship between permeability and pore uniformity, throat uniformity, and combined pore-throat uniformity is better than porosity. There is a negative correlation between porosity uniformity and porosity, and the correlation coefficient (R\({}^{2}\)) is 0. 525, indicating that the greater the porosity uniformity, the more uniform the development of pores, and the smaller the reservoir porosity. The throat uniformity is positively correlated with porosity, and the correlation coefficient (R\({}^{2}\)) is 0.653. This indicates that the greater the throat uniformity, the more uniform the throat development, and the greater the porosity. There is a positive correlation between pore-throat joint uniformity and porosity, and the correlation coefficient (R\({}^{2}\)) is 0.709. It is proved that the greater the combined pore-throat uniformity, the smaller the difference of pore-throat size; the weaker the heterogeneity of pore-throat distribution, the weaker the pore-throat aggregation phenomenon; and the smaller the probability of pore-throat overlap; the larger the effective porosity of the reservoir [20,21]. A comparative \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Number** & **Reservoir Types** & **Porosity (\%)** & **Permeability (10\({}^{-3}\)\(\upmu\)m\({}^{2}\))** &
\begin{tabular}{c} **Combined Pore-Throat** \\ **Uniformity** \\ \end{tabular} \\ \hline
1 & Macro pore-fine throat & 12.51 & 0.288 & 0.7708 \\
2 & Macro pore-micro throat & 8.44 & 0.021 & 0.12408 \\
3 & Macro pore-micro throat & 9.77 & 0.031 & 0.14598 \\
4 & Macro pore-fine throat & 11.28 & 0.454 & 0.7301 \\
5 & Macro pore-micro throat & 8.98 & 0.106 & 0.5078 \\
6 & Macro pore-thin throat & 11.0 & 0.31 & 0.7693 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The combined pore-throat uniformity of different pore-throat combination reservoir. analysis shows that the uniformity of throat development controls the effectiveness of reservoir space. The porosity uniformity is negatively correlated with the permeability, and the correlation coefficient (R2) is 0.749. This indicates that the greater the porosity uniformity, the more uniform the development of pores, and the lower the permeability. There is a positive correlation between throat uniformity and porosity, and the correlation coefficient (R2) is 0.9397. The greater the throat uniformity, the more uniform the throat development, and the greater the permeability. There is a positive correlation between the combined pore-throat uniformity and permeability, and the correlation coefficient (R2) is 0.978. This indicates that the greater the combined pore-throat uniformity, the more uniform the radius of pore throat development, and the greater the permeability. Through a comparative analysis, it is found that the uniformity of throat controls the reservoir and seepage capacity of the Chang 63 tight sandstone reservoir in the study area. At the same time, the relationship between movable fluid saturation and pore uniformity, throat uniformity, and pore-throat combination uniformity of different pore-throat combination types was analyzed by using NMR technology (Figure 3). It can be found that the movable fluid saturation is positively correlated with throat uniformity and pore-throat combination uniformity. The porosity uniformity is negatively correlated with movable fluid saturation. Thus, the uniformity of throat development controls fluid mobility in the pore system of the reservoir and restricts oil recovery. Figure 3: Relationship between movable fluid saturation and pore uniformity, throat uniformity, combined pore-throat uniformity.