## 3 Results and Discussion
### Relative Phase Permeabilities  
The calculated relative permeability of wetting (water) and non-wetting (oil) phases before (gray lines) and after (black lines) rock dissolution are illustrated in Figures 10 and 11. As can be seen from these figures, the relative phase permeability curves changed differently during rock dissolution. In general, for all considered sub-volumes of both samples, an increase in the relative permeability of water and oil was observed as a result of the dissolution of carbonate rock (Figures 10 and 11). Almost all sub-volumes, before their dissolution, could be characterized as water-wet, characterized by low relative water permeability and an almost linearly decreasing relative oil permeability with increasing water saturation. As Figure 10 displays, as a result of rock dissolution, a noticeable change in the relative phase permeability curves occurred in sub-volumes A2 and A3, while for the remaining sub-volumes, they practically did not change, with the exception of a slight decrease in the relative oil permeability. The significant increase in the relative water permeability of sub-volume A3 after rock dissolution may indicate a change in its wettability from water-wet to mixed-wet. Despite a noticeable increase in the relative water permeability after rock dissolution of sub-volume A3, its relative oil permeability increased significantly due to dissolution, which helped increase its mobility. Figure 10 also shows that the relative oil permeability curve of sub-volume A3 sharply decreases around the residual oil saturation. It is noteworthy that sub-volume A3 has a relatively high initial absolute permeability, and its increase is moderate (67%) among the permeability increases of the other sub-volumes from sample A (Figure 9a). Furthermore, this sub-volume (A5) has the smallest increase (1.1%) in porosity (Figure 9a), despite having the highest initial porosity (see Table 4). For sub-volume A2, the relative oil permeability after rock dissolution was placed higher than the pre-dissolution one for water saturations above 0.3, although the relative water permeability is still relatively low (Figure 10). Interestingly, this sub-volume (A2) had its upper boundary of the pore radius range decrease by almost 5%, whereas all other sub-volumes from both samples showed an increase (see Table 3). Figure 11 demonstrates a significant increase in relative oil permeability after rock dissolution for sub-volumes B1 and B3-B5, which experienced substantial increases in porosity and absolute permeability (Figure 9a), while their relative water permeability shows a comparatively low increase as a result of rock dissolution. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sub-Volume**} & \multicolumn{2}{c}{**Porosity, \%**} & \multicolumn{2}{c}{**Absolute Permeability, D**} \\ \cline{2-5}  & **Before** & **After** & **Before** & **After** \\ \hline A1 & 16.7 & 22.2 & 2.58 & 11.13 \\ \hline A2 & 19.4 & 21.3 & 3.86 & 9.01 \\ \hline A3 & 29.1 & 29.4 & 24.53 & 40.94 \\ \hline A4 & 21.8 & 23.1 & 8.95 & 12.86 \\ \hline A5 & 19.8 & 2  
As Figures 10 and 11 illustrate, for all sub-volumes there is a significant change in critical points of the relative phase permeability curves, such as the residual oil and water saturations and the lower and upper boundaries of the range of water saturation variation, which are given in Table 5. As Table 5 describes, the residual oil saturation increased only in sub-volumes A1, A4, and A5, for which the relative phase permeabilities decreased insignificantly (Figure 10), while for the other sub-volumes, it decreased significantly. Figure 10: Relative phase permeabilities of sub-volumes from sample A. As Table 5 also shows, the decrease in residual oil saturation is greater for sub-volumes of sample B than for sub-volumes of sample A. The decrease in residual oil saturation indicates that the pores have widened as a result of rock dissolution, which has led to increased oil mobility.