## 3 Results and Discussion
### Floatation Test Results  
Figure 5 shows the results of the flotation tests. After aging, oil-wet samples were produced; depending on the role of the nanofluid, they were separated into oil- and water-wet powders. The light oil-wet powder floated, whereas the heavy water-wet powder settled at the bottom. The results for the samples under varying nanoparticle concentrations, reaction times, and reaction temperatures were difficult to confirm visually; however, they were separated into different phases. Particle concentration was set to 0-3 wt.% to examine its influence, whereas other variables, such as reaction time and temperature, were fixed at 24 h and 75 \({}^{\circ}\)C, respectively. Considering that the change in wettability is significantly affected by the reactivity of nanoparticles on the rock particle surface, an increase in particle concentration can potentially lead to an increase in reactivity. In addition, an increase in the fluid particle concentration can affect the stability of the nanoparticle dispersion. Figure 6 shows the values of %WW as a function of particle concentration. For limestone, the hydrophilic sample  
Figure 5: Floatation test results of rock powder with limestone (left) and dolomite (right). (**a,b**) Effects of nanoparticle concentrations. The oil phase and oil-wet particles are removed, leaving the water-wet particles. (**c,d**) Effects of reaction time. The mixture is vigorously mixed with brine and then placed in the oven for 1 day, causing the oil-wet particles to float, whereas the water-wet particles settle. (**e,f**) The effects of treatment temperature are similar to those of reaction time. exhibited a ratio of 52.3% in the absence of nanoparticles. With the reaction of nanoparticles, the %WW increased to 68-97.75%, indicating a significant change in wettability owing to the nanoparticle reaction. For dolomite, the base fluid exhibited approximately 73% of %WW. Furthermore, the ratio of the hydrophilic sample gradually increased from 83% to 98% with increasing nanoparticle concentration. Similarly, changes in the wettability of the oil-wet samples were observed. Limestone had a higher initial oil-wet ratio, whereas dolomite was more sensitive to the concentration of rock particles. Thus, an improvement in wettability occurs in both limestone and dolomite when they react with nanoparticle-containing fluids. Furthermore, the extent of improvement increases with dolomite concentration. Moreover, limestone showed wettability improvement regardless of concentration. This indicates that particle surface characteristics can influence reactivity, highlighting the need for particle concentration control based on the rock composition in the reservoir. To assess the effect of reaction time, the nanoparticle concentration was set to 1 wt.%, and the reaction temperature was fixed to 75 \({}^{\circ}\)C, with analyses conducted over 6-72 h. Figure 7 shows the values of %WW as a function of reaction time with nanofluid. In the case of limestone, slight variations in %WW were observed over time. However, all samples exhibited differences of less than 3% for dolomite. The impact of reaction time was not clear, and wettability improved irrespective of time. However, considering the distinctive characteristics of powdered samples with significantly higher surface areas than the actual core samples, the reactivity between nanoparticles and rock surfaces may be overstated. Hence, it is important to recognize the need for analyzing the results of core flooding experiments. To examine the influence of temperature, the concentration of the nanofluid was fixed to 1 wt.%, and the reaction time was set to 24 h. Figure 8 shows the %WW as a  
Figure 6: Effect of particle concentrations of SNPs on flotation test results. Figure 7: Effect of reaction time on flotation test results. function of temperature.