## 2 Material and Methods
### Surface Characterization
#### 2.6.3 Contact Angle Goniometry  
The drop shape analysis profile (DSA-P) device from [PERSON](tm), shown in Figure 7a, uses the sessile drop technique to obtain a measure of the angle resulting from the spreading of a liquid droplet on a solid surface. A syringe deposits a drop of liquid (volume between 10 and 20 \(\upmu\)L) above the surface, and a dedicated software performs an image analysis of the profile obtained through a high-resolution camera (Figure 7b). Two techniques have been used, the static and dynamic contact angle measurements. In the first case the angle is measured immediately after the drop has been deposited; in the second one, the whole instrument is tilted up to 90\({}^{\circ}\) and the shape analysis is carried out at the moment the drop starts gliding. Within the last method, a receding and an advancing angle is obtained, with the latter corresponding to the tilting direction. Figure 6: (**a**) [PERSON](tm) “dimension icon” Atomic Force Microscope [15] with the Scanasyst-Air® probe [16] on the right top corner. (**b**) Typical cycle of force vs. time in the Peak Force Tapping mode. The dynamic technique is normally selected for chemically heterogeneous materials, such as our resin-saturated chalks. By introducing the measured advancing angle \(\theta_{\text{tot}}\) in the following [PERSON]'s law [17; 18]:  
\[\cos\theta_{\text{tot}}=X_{\text{c}}\cos\theta_{\text{c}}+X_{\text{r}}\cos \theta_{\text{r}} \tag{2}\]  
we obtain the angle \(\theta_{\text{c}}\) corresponding to the chalk contribution only, knowing the surface fraction of the resin \(X_{\text{r}}\) and chalk \(X_{\text{c}}\) and the dynamic contact angle \(\theta_{\text{r}}\) for a sample made up only of the same resin used to saturate the rocks. Assuming the resin totally filled the pores, \(X_{\text{r}}\) corresponds to the rock porosity \(\varphi\), and consequently \(X_{\text{c}}=(1-\varphi)\). The contact angle for chalk depends of the free surface energy of the interface between chalk and the liquid used in the experiment. The surface free energy of chalk is hereby determined with the Owens-Wendt (OW) method [19], which defines the surface energy as the sum of two components: (1) dispersive forces \(\gamma^{\text{(D)}}\) and (2) dipole-dipole interaction \(\gamma^{\text{(P)}}\) between permanent or induced dipoles (e.g., hydrogen bonds) [20] according to:  
\[\frac{\gamma_{\text{I}}(\cos\theta_{\text{c}}+1)}{2\bigg{(}\sqrt{\gamma_{ \text{I}}^{\text{(D)}}}\bigg{)}}=\sqrt{\gamma_{\text{s}}^{\text{(P)}}}\frac{ \sqrt{\gamma_{\text{I}}^{\text{(P)}}}}{\sqrt{\gamma_{\text{I}}^{\text{(D)}}} }+\sqrt{\gamma_{\text{s}}^{\text{(D)}}} \tag{3}\]  
where the superscripts of the surface energy \(\gamma\) refer to the polar (P) and dispersive (D) components, while the subscripts refer to the liquid (I), chalk (c), and solid (s). The known parameters are the polar and dispersive components of the liquids used (from the literature) and the derived angle for the chalk, from Cassie's law. By plotting the known parameters for at least two fluids (one polar and one apolar to ensure sufficient dispersion), a linear regression provides the intercept \(\sqrt{\gamma_{\text{s}}^{\text{(D)}}}\) and slope \(\sqrt{\gamma_{\text{s}}^{\text{(P)}}}\), which yield the dispersive and polar components of the solid phase, the sum of which gives the total surface free energy. To insure better accuracy, five different fluids were used, with known polar and dispersive components given in \(\text{mJ}/\text{m}^{2}\) in Table 2.  
To establish the effect of salt type and concentration on wettability, we additionally measured the static contact angle on two pure calcite crystals (Figure 5), using NaCl and MgCl\({}_{2}\) aqueous solutions with increasing salinity from 0.04 to 0.60 mol/L. We also estimated the roughness of the tested materials by means of a laser scanning confocal microscope LSM 710 from Zeiss(tm) and the same Atomic Force Microscope used for adhesion characterization.