## 4 Results
### Petrographic and Chemical Characterization of Carbonate Rocks after SC CO\({}_{2}\) Injection  
#### 4.2.1 Dry SC CO\({}_{2}\)  
On the thin section scale, no changes (either dissolution or precipitation) could be detected by OpM and OIA on the carbonate samples after their exposure to dry CO\({}_{2}\). The optical properties of the rock forming minerals did not present any kind of alteration, neither was the value of the optical porosity modified by the experiment. We can confirm thus that, at least at the scale of the microscopic  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Component** & **Rock before** & **Rock after Dry** & **Interpretation** & **Rock after CO\({}_{2}\) and** & **Interpretation** \\  & **CO\({}_{2}\) (\%) (I)** & **CO\({}_{2}\) (\%) (2)** & **(1) to (2)** & **Brine (\%) (3)** & **(1) to (3)** \\ \hline SiO\({}_{2}\) & 2.080 \(\pm\) 0.170 & 2.150 \(\pm\) 0.176 & & 2.510 \(\pm\) 0.206 & \\ Al\({}_{2}\)O\({}_{3}\) & 0.620 \(\pm\) 0.072 & 0.630 \(\pm\) 0.073 & & 0.720 \(\pm\) 0.083 & \\ Fe\({}_{2}\)O\({}_{3}\) & 0.250 \(\pm\) 0.024 & 0.240 \(\pm\) 0.023 & & 0.400 \(\pm\) 0.38 & \\ MnO & 0.200 \(\pm\) 0.001 & 0.150 \(\pm\) 0.014 & & 0.050 \(\pm\) 0.005 & \\ MgO & 0.980 \(\pm\) 0.078 & 0.860 \(\pm\) 0.068 & & 1.13 \(\pm\) 0.900 & \\ CaO & 52.810 \(\pm\) 3.590 & 54.150 \(\pm\) 3.682 & No relevant & 52.200 \(\pm\) 3.545 & No relevant \\ Na\({}_{2}\)O & 0.070 \(\pm\) 0.005 & 0.080 \(\pm\) 0.007 & changes & 0.065 \(\pm\) 0.005 & changes \\ K\({}_{2}\)O & 0.320 \(\pm\) 0.064 & 0.410 \(\pm\) 0.082 & & 0.340 \(\pm\) 0.068 & \\ TiO\({}_{2}\) & 0.040 \(\pm\) 0.003 & 0.040 \(\pm\) 0.003 & & 0.100 \(\pm\) 0.010 & \\ P\({}_{2}\)O\({}_{3}\) & 0.010 \(\pm\) 0.001 & 0.010 \(\pm\) 0.001 & & 0.045 \(\pm\) 0.005 & \\ LOI & 42.580 \(\pm\) 5.111 & 40.720 \(\pm\) 4.886 & & 41.5 \(\pm\) 4.980 & \\ \hline Total & 99.810 & 99.830 & & 99.60 & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Chemical composition of whole rock (vuggy carbonates) before (1: initial conditions) and after the experiment (2: dry CO\({}_{2}\) conditions and 3: wet CO\({}_{2}\) conditions). Uncertainty given by IGME Laboratory (SiO\({}_{2}\) 8.20%; Al\({}_{2}\)O\({}_{3}\) 11.57%; Fe\({}_{2}\)O\({}_{3}\) 9.55%; MnO 9.31%; MgO 7.96%; CaO 6.80%; Na\({}_{2}\)O 8.20%; K\({}_{2}\)O 19.94%; TiO 2 8.37%; P\({}_{2}\)O\({}_{5}\) 12%).  
Figure 3: Characteristic textural features of the vuggy carbonates observed by OpM (**a,d**) and SEM (**b,c**).  
observations, the mineralogical and textural configuration of the rock remained intact and none of the possible processes (e.g., pore filling by precipitations, increased surface roughness by dissolution, recrystallization, etc.) took place. Observations carried out with SEM also showed a lack of evidence of dissolution or precipitation of the main mineral components. The Cal/Dol ratio remained the same as in the original samples and the qualitative assessment of the calcite and dolomite grain morphology did not show any evident shape changes provoked by the CO\({}_{2}\) exposure. The analysis of the chemical composition of samples after dry CO\({}_{2}\) exposure (Table 1 \"Rock after dry CO\({}_{2}\)\" column) provided values within the uncertainty ranges of the original values, which again confirms the non-existence of reactions between the rock forming minerals and the dry SC CO\({}_{2}\).