## 3 Results
### Petrophysical Calculations from Micro-Tomography Images
Normandie and Lexos mostly have a good connectivity, except for one Lexos sample with only 55% of percolating and therefore a very low connectivity. At this stage, it should be noticed that data from laboratory measurements and images calculations are in the same order of magnitude and are similar and comparable. A comparison between the two characterization techniques will be done later. In the same way as the previous section, even if samples inside rock types have similar properties, groups can be formed with correlated properties. Concerning Normanide, two groups emerged from data. With the lowest proportion of \(PV\), N03 and N05 both have bad-connected poral phase, supported by the lowest permeabilities. They also present a high proportion of small pores with diameters between the pixel size and 36 \(\upmu\)m (Figure 5), consistent with their high \(\lx@sectionsign\). Contrarily, N02, N04, N08 and N09 have a very well-connected poral phase. N02 and N09 have moderated permeabilities and \(\lx@sectionsign\), while N04 and N08 are very permeable and have low proportion of small pores, extracted from chord lengths calculations. Inside each couple, N04, N05 and N09 have better connectivity induced by a higher proportion of transverse pores (Figure 6). N04 also has low electrical factors [8; 40], which is consistent with a better connection. At this point, it seems important to notice that a low proportion of small pores is consistent with a high permeability [27]. Moreover, it can be noticed that a high proportion of transverse small pores (X and Y directions) is consistent with a low tortuosity. Figure 5: Pore size distribution obtained by sphere diameters calculations (on the top) and mean chord lengths calculations (on the bottom), using imaging software. Normandie samples are displayed on the left part, Euville on the central part and Lexos is shown on the right. Concerning Euville, there are no particular couples which appear, they all present very good connected poral phase. However, it can be said that E04 and E08 are very different, while E02 and E05 oscillate between the two, depending on the chosen parameters. Indeed, E04 is the sample with the smallest electrical parameters and the highest permeability, suggesting a good connectivity. There is no significant differences in proportion of pores smaller than 36 \(\upmu\)m calculated by sphere diameters distribution (Figure 5), but by chord lengths distribution, E02 counts the highest proportion of small pores, while E08 the lowest. This explains the difference in \(\lx@sectionsign\)5 between E02 and E08. It should be noticed that E02 displays spherical pores, while E05 and E08 have more transverse connections (Figure 7). However, even with more transverse connections, E08 has too few pores in Z directions, implying a very poor permeability and a high tortuosity, which decrease significantly its connectivity. Finally, Lexos samples present a lot of variability. As written above, L03 and L07 do not present percolation path. This is consistent with their very high \(\lx@sectionsign\)5, induced by a high quantity of pores around 12 \(\upmu\)m, as it has been seen in centrifugation (Section 3.1, Figure 4) and from chord length analysis displayed in Figures 5 and 8. They also have  
Figure 6: Chords length distribution for Normandie samples, pore diameters are displayed by proportion. On the top left, an average of chord lengths in the three directions is shown. The rest detail chord lengths in directions X, Y and Z: on the top right, there are N03 and N05, on the bottom left, N02 and N09, while on the bottom right, there are N04 and N08. Figure 7: Chords length distribution for Euville samples, pore diameters are displayed by proportion. On the left, an average of chord lengths in the three directions is shown. On the middle and right, chord lengths are detailed in directions X, Y and Z: E02 and E04 on the middle and E05 and E08 on the right. around 25% of pores in \(Z\) direction, implying few transverse connections and therefore low connectivity and permeability.