## 3 Results and Discussion
### Analysis of Polymer
#### 3.2.2 Influencing Factors of Polymer  
In order to study whether the QJ75-39 sample was suitable for the Lu block A reservoir conditions, the influences of temperature, salinity and aging time on the 2000 mg/L polymer solution were investigated. In the experiment, in order to reduce the error, measurements were taken three times at each point and the average value was taken. Figure 9 shows the viscosity curves of the polymer under different influencing factors. \begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **QJ75-39** \\ \hline Solid content (\%) & 90.14 \\ Molecular weight (\(\times 10^{6}\)) & 6.43 \\ Intrinsic viscosity (mL/g) & 1163 \\ Filter ratio & 1 \\ Residual monomer (\%) & 0.01 \\ Degree of hydrolysis (\%) & 5.2 \\ Insoluble fraction (\%) & 0.008 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary of physical and chemical properties. Figure 9: Influencing factors for the polymer. Effect of Temperature  
Figure 9A shows the viscosity curve of the polymer 2000 mg/L solution at 40-95 \({}^{\circ}\)C. As shown in Figure 9A, the viscosity of the polymer solution decreased with the increase in the temperature. The synthesized polymer QJ75-39 had better temperature resistance than the conventional polymer HPAM. When the temperature reached 95 \({}^{\circ}\)C, the viscosity of the synthesized polymer QJ75-39 was 31.3 mPa-s, while that of the conventional polymer HPAM was 5.1 mPa-s. The viscosity of QJ75-39 was much higher than HPAM at 95 \({}^{\circ}\)C. This was mainly due to the fact that the movement of the HPAM molecular chain accelerated with the increase in the temperature, and the spatial network structure of HPAM was destroyed to some extent. The higher the temperature was, the lower the viscosity. The synthesized polymer had better temperature resistance than conventional polymers. When the temperature reached 95 \({}^{\circ}\)C, the viscosity of the synthesized polymers was 31.3 mPa-s, which was mainly a result of the introduction of DS-16 hydrophobic monomers and AMPS monomers. DS-16 and AMPS have strong hydrophilic groups, so they can effectively inhibit the viscosity loss caused by the hydrogen bond breakage of amide and carboxyl groups. Effect of Salinity  
Figure 9B shows the salinity tolerance of the polymer at 95 \({}^{\circ}\)C. It can be seen from the experimental results that the polymer had good salinity tolerance under different salinity conditions. When the TDS was 27,688.4 mg/L, the viscosity of the polymer was only 26.3 mPa-s. When the TDS was 166,130.4 mg/L, the viscosity of the polymer was 32.8 mPa-s. The viscosity of the polymer increased slowly with the increase in salinity. This was because the introduction of salinity into the solvent shielded the electrostatic repulsion, produced dehydration, caused the molecular chain to curl up, reduced the hydrodynamic size and reduced the apparent viscosity of the common polymer solution. However, hydrophobically associating polymers form supramolecular aggregates through intermolecular association, and the supramolecular aggregates can connect with each other to form a uniform, three-dimensional network structure covering the whole system under static conditions. The formation and disassembly of the three-dimensional network structure changed reversely with the increase or decrease in the degree of hydrophobic association. The introduction of salinity also increased the polarity of the solvent, meaning that stronger association of hydrophobic groups resulted in larger hydrodynamic size and greater apparent viscosity for the polymer solution, making the polymer show good salinity tolerance. Effect of Aging  
Polymer flooding is a long-term process, so the aging stability of polymer solution and the long-term effectiveness of polymer solution viscosity are very important for polymer flooding. When the injected polymer is intended to exist in the formation for a long time, it must have good aging stability. Figure 9C shows the viscosity changes in polymers at different aging times (95 \({}^{\circ}\)C, 53,376.8 mg/L).