**6. Contact angle data comparison**

As shown in **Figure 7**, an invariant IFT vs. "aqueous and CO<sup>2</sup>

measurements and molecular simulations) of CO<sup>2</sup>

phase, is more than double for CaCl<sup>2</sup>

solution.

Shah et al. [21] conducted water-H<sup>2</sup>

S, SO<sup>2</sup>

, N<sup>2</sup>

S:CO<sup>2</sup>

**Figure 7.** Effect of phase density difference on IFT for the CO<sup>2</sup>

cluded a strong decrease of IFT with increase in H<sup>2</sup>

decrease in IFT (i.e. from 29 mN/m in the case of pure CO<sup>2</sup>

Chalbaud et al. for CO<sup>2</sup>

176 Carbon Capture, Utilization and Sequestration

case of CaCl<sup>2</sup>

of 6 wt% SO<sup>2</sup>

The influence of H<sup>2</sup>

water-(30, 70 mol% H<sup>2</sup>

complex between SO<sup>2</sup>

irrespective of the pressure and temperature until a Δρ of about 600 kg/m3


analyzation of their IFT data along with Chiquet et al. [18] water-CO<sup>2</sup>

increase in IFT with Δρ was reported by Bikkina et al. [15]. Similar trends were reported by

There has been a common agreement on the effect of salinity on IFT data (from experimental

At a given pressure and temperature condition, IFT was observed to increase with salinity. Aggelopoulos et al. [22] reported that the increase in IFT, at a given molality of aqueous

Chalbaud et al. [13], and this increase was attributed to the presence of divalent cations in the

by Shah et al., Saraji et al., Al-Yaseri et al., and Kravanja et al., respectively [21, 26, 28, 42].

suggested as the probable reason for the decrease in IFT. Pressure, temperature, and salinity conditions used in their experiments were 3000 psig, 60°C, and 1 M brine, respectively.

, and Ar contamination in CO<sup>2</sup>

phase density difference (Δρ)"


stream on IFT were investigated

IFT data, they con-

. A significant linear

to 18 mN/m in the presence

solution compared to that of NaCl solution reported by

S IFT measurements up to 15 MPa and at 120°C and

) IFT measurements up to 15 MPa and at 77°C. Upon combined

) was reported by Saraji et al. [42]. The presence of weakly bounded surface

and water molecules at the supercritical fluid/liquid interface was

S content in CO<sup>2</sup>


and then a steep

There is a significant scatter in the reported CA (wettability) data [30, 54]. The reported CA data include static [23, 30, 31, 41] and dynamic [16, 27, 30, 32, 33, 35, 38, 42, 55] CAs. The data also include measurements of water/brine droplet on substrate in CO<sup>2</sup> [23, 26, 27, 30, 31, 33, 38, 41] and CO<sup>2</sup> bubble/droplet on substrate immersed in aqueous phase [34, 35, 41, 42, 54, 55]. One of the major reasons for the apparent spread in CA data is in fact due to the comparison of the data collected at significantly different process parameters. For example, the CA data collected on quartz substrates having orders of magnitude, different surface roughness values, and at different temperatures and salinities were compared [38]. Similar inappropriate comparisons were also made for calcite [33] and mica substrates [27]. It should also be noted that even static and dynamic CAs have been compared [27, 33].

It is possible that the so-called smooth and pure substrates used for some of the published data may have surface chemical and physical heterogeneity which could cause significant CA hysteresis (i.e., the difference between advancing and receding CAs). In general, static CA falls somewhere between the advancing and receding CAs [73]. Hence, it is inappropriate to compare static and dynamic CAs. Some researchers reported surface roughness data of their substrates [16, 27, 32–34, 38, 41, 42, 74]. The reported quartz surface roughness data range from 0.5 to 1300 nm (5 orders of magnitude). In the case of mica, Wang et al. [34] used phlogopite mica with 250 nm surface roughness and Arif et al. [27] used muscovite mica with a roughness value of 12 nm.

Al-Yaseri et al. thoroughly investigated the influence of surface roughness on advancing and receding CA trends of quartz-CO<sup>2</sup> -water system using the substrates of different surface roughness (RMS) values: 56, 210, 560, and 1300 nm [32]. They found that as the roughness increases from 56 to 1300 nm, advancing and receding CAs at 296 K and 10 MPa decrease by ~6.5 and ~2°, respectively, whereas at 323 K, the CAs decrease by ~14 and ~14°, respectively. The effect of surface roughness on advancing and receding CA trends of calcite-CO<sup>2</sup> -water system was studied by Arif et al. using calcite substrates of surface roughness (RMS) values: 7.5, 30, and 140 nm [33]. They noted that as the roughness increases from 7.5 to 140 nm, both the advancing and receding CAs at 323 K and 15 MPa decrease by ~10°. There have not been any systematic experimental studies reported on the influence of surface roughness on CA of mica-CO<sup>2</sup> -water system.

Al-Yaseri et al. and Arif et al. measured advancing and receding CAs on quartz and calcite substrates placed on 12° and 15° (w.r.t horizontal) tilted bases, respectively. About a 6 μl water droplet that was not pre-saturated with CO<sup>2</sup> was dispensed on to the titled substrate and the advancing and receding CAs were measured on droplet images extracted from the recorded video [32, 33].

droplet was placed at 0.1 MPa. Bikkina [31] reported a significant shift in CA towards less

proposed as the possible mechanism for the observed CA shift, and hence the CA measure-

were 8.5 MPa, 318 K, and 0.01–5 M NaCl. The pore-scale CAs were observed to increase from

For calcite substrate, at ~298 K, both Espinoza and Santamarina [23] and Bikkina [31] reported a sudden dip (~6°) in the CA at the phase changing pressure. The CA values reported by

responding values reported by Espinoza and Santamarina [23] were 35 and 30°, respectively.

and 0.9% quartz) system at 10 MPa and 323 K, after secondary imbibition. The observed CA

CAs, so it appears that the CAs are neither static nor dynamic. It should be noted that the dissolution occurred irrespective of using pre-equilibrated fluids. If there exists evaporation/ dissolution of the droplet, the corresponding CA can increase, decrease, or stay constant depending upon the relative molecular forces among the three phases involved and the triple line movement [77–79]. Farokhpoor et al. [35] reported that water/brine receding CAs on quartz and calcite and no significant effect of pressure on the CAs were observed. They reported increase in CAs with temperature and salinity for quartz substrate, but a decrease in

Three significantly different CA trends with pressure have been reported for quartz/silica: (1) no or insignificant change in CA [23, 31, 35, 69]; (2) sudden increase in CA near the phase changing pressure [40–42]; and (3) asymptotic increase in CA with increase in pressure [32, 64]. Al-Yaseri et al. found a remarkable linear correlation between CA and density of gas for quartzbrine (4.48 M = 20 wt% NaCl +1 wt% KCl) system [80]. The correlation is applicable for a wide

and receding CAs (using drop addition and withdrawal method) on quartz at 3000 psig, 60°C, and 1 M NaCl. They observed insignificant difference in the CAs with 1 and 6 wt% SO<sup>2</sup>

were used as aqueous and gas phases, and the CA measurements were conducted at 13 MPa and 333 K. They reported 47 ± 3.4°, 33.9 ± 6°, and 40.6 ± 3.9° water advancing CAs for CO<sup>2</sup>

contamination on water advancing CA on quartz was studied by Al-Yaseri et al. [26]

contamination in CO<sup>2</sup>

at the same pressure, temperature, and salinity. Effect


range of gases. Temperature was found to change the slope of the correlation.

using drop addition method. About 5000 ppm NaCl brine and 50:50 mol% CO<sup>2</sup>

mixture-brine, and N<sup>2</sup>

gaseous region and 42–40° in the CO<sup>2</sup>

as droplet phase may not observe this phenomenon due to insuf-

Interfacial Tension and Contact Angle Data Relevant to Carbon Sequestration

. The tested pressure, temperature, and salinities

http://dx.doi.org/10.5772/intechopen.79414

, and the highest CA increase was observed in the case

volume [75]. Kim et al. (2012) observed a dewetting phenomenon in brine-filled

physisorbed water and subsequent capping of the silanols (on quartz surface) by CO<sup>2</sup>

. Desorption of

liquid region. The cor-


:N<sup>2</sup>

com-

mixture



bubble/droplets as water/brine advancing

were

179

water-wet state upon repeated exposure of the substrates to liquid or scCO<sup>2</sup>

ment systems with CO<sup>2</sup>

silica micromodels upon exposure to scCO<sup>2</sup>

values were in the range of 35 and 55° [37].

CA with salinity for calcite substrate.

Saraji et al. [42] studied the influence of SO<sup>2</sup>

:N<sup>2</sup>

pared to those measured for pure CO<sup>2</sup>

brine, 50:50 mol% CO<sup>2</sup>

of N<sup>2</sup>

Wang et al. [34] reported CAs of dissolving CO<sup>2</sup>

Andrew et al. performed pore-scale CA measurements for CO<sup>2</sup>

near 0 to 80° upon exposure to scCO<sup>2</sup>

Bikkina [31] were 45–48° in CO<sup>2</sup>

ficient CO<sup>2</sup>

of 5 M brine [76].

Al-Yaseri et al. [32], Arif et al. [27], and Arif et al. [33] also investigated the effect of pressure, temperature, and salinity on advancing and receding CAs of quartz-CO<sup>2</sup> -water, mica-CO<sup>2</sup> water, and calcite-CO<sup>2</sup> -water systems, respectively. The pressure, temperature, and salinity ranges studied for quartz, mica, and calcite substrates were: 0.1–20 MPa, 296–343 K, and 0–35 wt% (NaCl, CaCl<sup>2</sup> , and MgCl<sup>2</sup> ); 0.1–20 MPa, 308–343 K, and 0–30 wt% NaCl; and 0.1– 20 MPa, 308–343 K, and 0–20 wt% NaCl, respectively. For both quartz and calcite substrates, advancing and receding CAs increased with pressure, but the effect of temperature was different for the substrates. Both the advancing and receding CAs increased with temperature in the case of quartz, but the opposite trend was reported for calcite. In the case of quartz, both the advancing and receding CAs increased with salinity and the increase was higher for MgCl<sup>2</sup> , followed by CaCl<sup>2</sup> and NaCl. Whereas in the case of calcite, salinity has negligible effect on both the advancing and receding CAs up to 5 wt% NaCl and the CAs increased with salinities above 5 wt% NaCl. The effect of pressure and temperature on advancing and receding CA trends of mica was similar to that of calcite. The effect of salinity on mica CA was similar to that of quartz.

Broseta et al. conducted water/brine advancing and receding CA measurements on quartz, calcite, and mica substrates [40]. For quartz, insignificant change in receding CAs with pressure (0.5–14 MPa) and salinity (0.08–6 M NaCl) was observed, whereas increase in the advancing CAs with the pressure and salinity was reported. For calcite, the receding and advancing CAs increased by 8 and 15°, respectively, with pressure (0.5–14 MPa) at 0.08 M and 308 K. In case of mica, the change in receding CAs with pressure was less than 10°, but a significant increase (up to ~40°) in advancing CAs with pressure was observed when there was CO<sup>2</sup> adhesion to mica. However, when there was no CO<sup>2</sup> adhesion, the increase in advancing CAs with pressure was only about 10°. Wan et al. also observed CO<sup>2</sup> adhesion on mica and similar levels of hysteresis in CA; however, they did not observe any clear CA trends with pressure and salinity [54].

Espinoza and Santamarina [23] and Bikkina [31] measured static CAs by placing a single aqueous fluid droplet on substrate (quartz/calcite) at a given temperature and pressure and successively injected CO<sup>2</sup> into the measurement cell to increase the system pressure. For quartz substrate at 298 K (below critical temperature of CO<sup>2</sup> , Tc,CO2), they did not observe any significant effect of pressure on CA, both in gaseous and liquid regions; however, the values reported by Espinoza and Santamarina [23] and Bikkina [31] were ~20 and ~45°, respectively. At 313 and 323 K (i.e., above Tc,CO2), Bikkina [31] observed about 5° increase in CA in gaseous region compared to 298 K and the CA gradually decreased in supercritical region. The surface roughness values of the substrates used were not reported in both the above studies. Bikkina [31] used equilibrated fluids and the droplet was placed on the substrate at 1.48 MPa, whereas Espinoza and Santamarina [23] used non-equilibrated fluids and the droplet was placed at 0.1 MPa. Bikkina [31] reported a significant shift in CA towards less water-wet state upon repeated exposure of the substrates to liquid or scCO<sup>2</sup> . Desorption of physisorbed water and subsequent capping of the silanols (on quartz surface) by CO<sup>2</sup> were proposed as the possible mechanism for the observed CA shift, and hence the CA measurement systems with CO<sup>2</sup> as droplet phase may not observe this phenomenon due to insufficient CO<sup>2</sup> volume [75]. Kim et al. (2012) observed a dewetting phenomenon in brine-filled silica micromodels upon exposure to scCO<sup>2</sup> . The tested pressure, temperature, and salinities were 8.5 MPa, 318 K, and 0.01–5 M NaCl. The pore-scale CAs were observed to increase from near 0 to 80° upon exposure to scCO<sup>2</sup> , and the highest CA increase was observed in the case of 5 M brine [76].

Al-Yaseri et al. and Arif et al. measured advancing and receding CAs on quartz and calcite substrates placed on 12° and 15° (w.r.t horizontal) tilted bases, respectively. About a 6 μl

and the advancing and receding CAs were measured on droplet images extracted from the

Al-Yaseri et al. [32], Arif et al. [27], and Arif et al. [33] also investigated the effect of pressure,

ranges studied for quartz, mica, and calcite substrates were: 0.1–20 MPa, 296–343 K, and

20 MPa, 308–343 K, and 0–20 wt% NaCl, respectively. For both quartz and calcite substrates, advancing and receding CAs increased with pressure, but the effect of temperature was different for the substrates. Both the advancing and receding CAs increased with temperature in the case of quartz, but the opposite trend was reported for calcite. In the case of quartz, both the advancing and receding CAs increased with salinity and the increase was higher

effect on both the advancing and receding CAs up to 5 wt% NaCl and the CAs increased with salinities above 5 wt% NaCl. The effect of pressure and temperature on advancing and receding CA trends of mica was similar to that of calcite. The effect of salinity on mica CA was

Broseta et al. conducted water/brine advancing and receding CA measurements on quartz, calcite, and mica substrates [40]. For quartz, insignificant change in receding CAs with pressure (0.5–14 MPa) and salinity (0.08–6 M NaCl) was observed, whereas increase in the advancing CAs with the pressure and salinity was reported. For calcite, the receding and advancing CAs increased by 8 and 15°, respectively, with pressure (0.5–14 MPa) at 0.08 M and 308 K. In case of mica, the change in receding CAs with pressure was less than 10°, but a significant increase (up to ~40°) in advancing CAs with pressure was observed when there was CO<sup>2</sup>

levels of hysteresis in CA; however, they did not observe any clear CA trends with pressure

Espinoza and Santamarina [23] and Bikkina [31] measured static CAs by placing a single aqueous fluid droplet on substrate (quartz/calcite) at a given temperature and pressure and

significant effect of pressure on CA, both in gaseous and liquid regions; however, the values reported by Espinoza and Santamarina [23] and Bikkina [31] were ~20 and ~45°, respectively. At 313 and 323 K (i.e., above Tc,CO2), Bikkina [31] observed about 5° increase in CA in gaseous region compared to 298 K and the CA gradually decreased in supercritical region. The surface roughness values of the substrates used were not reported in both the above studies. Bikkina [31] used equilibrated fluids and the droplet was placed on the substrate at 1.48 MPa, whereas Espinoza and Santamarina [23] used non-equilibrated fluids and the


); 0.1–20 MPa, 308–343 K, and 0–30 wt% NaCl; and 0.1–

and NaCl. Whereas in the case of calcite, salinity has negligible

into the measurement cell to increase the system pressure. For

temperature, and salinity on advancing and receding CAs of quartz-CO<sup>2</sup>

was dispensed on to the titled substrate

adhesion, the increase in advancing CAs

adhesion on mica and similar

, Tc,CO2), they did not observe any



water droplet that was not pre-saturated with CO<sup>2</sup>

, and MgCl<sup>2</sup>

recorded video [32, 33].

178 Carbon Capture, Utilization and Sequestration

water, and calcite-CO<sup>2</sup>

0–35 wt% (NaCl, CaCl<sup>2</sup>

similar to that of quartz.

and salinity [54].

successively injected CO<sup>2</sup>

, followed by CaCl<sup>2</sup>

adhesion to mica. However, when there was no CO<sup>2</sup>

with pressure was only about 10°. Wan et al. also observed CO<sup>2</sup>

quartz substrate at 298 K (below critical temperature of CO<sup>2</sup>

for MgCl<sup>2</sup>

For calcite substrate, at ~298 K, both Espinoza and Santamarina [23] and Bikkina [31] reported a sudden dip (~6°) in the CA at the phase changing pressure. The CA values reported by Bikkina [31] were 45–48° in CO<sup>2</sup> gaseous region and 42–40° in the CO<sup>2</sup> liquid region. The corresponding values reported by Espinoza and Santamarina [23] were 35 and 30°, respectively. Andrew et al. performed pore-scale CA measurements for CO<sup>2</sup> -brine-carbonate (99.1% calcite and 0.9% quartz) system at 10 MPa and 323 K, after secondary imbibition. The observed CA values were in the range of 35 and 55° [37].

Wang et al. [34] reported CAs of dissolving CO<sup>2</sup> bubble/droplets as water/brine advancing CAs, so it appears that the CAs are neither static nor dynamic. It should be noted that the dissolution occurred irrespective of using pre-equilibrated fluids. If there exists evaporation/ dissolution of the droplet, the corresponding CA can increase, decrease, or stay constant depending upon the relative molecular forces among the three phases involved and the triple line movement [77–79]. Farokhpoor et al. [35] reported that water/brine receding CAs on quartz and calcite and no significant effect of pressure on the CAs were observed. They reported increase in CAs with temperature and salinity for quartz substrate, but a decrease in CA with salinity for calcite substrate.

Three significantly different CA trends with pressure have been reported for quartz/silica: (1) no or insignificant change in CA [23, 31, 35, 69]; (2) sudden increase in CA near the phase changing pressure [40–42]; and (3) asymptotic increase in CA with increase in pressure [32, 64]. Al-Yaseri et al. found a remarkable linear correlation between CA and density of gas for quartzbrine (4.48 M = 20 wt% NaCl +1 wt% KCl) system [80]. The correlation is applicable for a wide range of gases. Temperature was found to change the slope of the correlation.

Saraji et al. [42] studied the influence of SO<sup>2</sup> contamination in CO<sup>2</sup> -rich phase on advancing and receding CAs (using drop addition and withdrawal method) on quartz at 3000 psig, 60°C, and 1 M NaCl. They observed insignificant difference in the CAs with 1 and 6 wt% SO<sup>2</sup> compared to those measured for pure CO<sup>2</sup> at the same pressure, temperature, and salinity. Effect of N<sup>2</sup> contamination on water advancing CA on quartz was studied by Al-Yaseri et al. [26] using drop addition method. About 5000 ppm NaCl brine and 50:50 mol% CO<sup>2</sup> :N<sup>2</sup> mixture were used as aqueous and gas phases, and the CA measurements were conducted at 13 MPa and 333 K. They reported 47 ± 3.4°, 33.9 ± 6°, and 40.6 ± 3.9° water advancing CAs for CO<sup>2</sup> brine, 50:50 mol% CO<sup>2</sup> :N<sup>2</sup> mixture-brine, and N<sup>2</sup> -brine systems, respectively.
