**5. Interfacial tension data comparison**

There have been a significant number of experimental and simulation studies on the IFT data of CO<sup>2</sup> -water/brine systems at typical reservoir pressure and temperature conditions. In general, a fair agreement in the trends and values can be observed in the data reported by various research groups [15, 20, 28, 29, 72]. **Figure 5** shows reproducibility of the effect of pressure on IFT data for CO<sup>2</sup> -water system at 298 K.

As shown in **Figure 5**, IFT sharply decreased with pressure when the CO<sup>2</sup> is gas and it becomes nearly constant when the CO<sup>2</sup> is liquid. It should be noted that Hebach et al., Bachu and Bennion, Bikkina et al., and Kravanja et al. used pendant drop method, whereas Chun et al. used capillary rise method [15, 20, 28, 29, 72]. The lowest IFT reported by Chun et al. [29] near the phase changing pressure was explained by Hebach et al. [72] as a potential consequence of the placement of thermocouple away from the droplet.

Similarly, IFT vs. pressure trends were also observed at above critical temperature of CO<sup>2</sup> rich phase, as shown in **Figure 6** [15]. Majority of the reported experimental and molecular simulations IFT data for CO<sup>2</sup> -water system show an increase in IFT with temperature when the CO<sup>2</sup> -rich phase is gas and the temperature is above the critical temperature and when CO<sup>2</sup> is gaseous phase [15–17, 20, 24, 29, 64, 72]. The increase in IFT with temperature is higher near the phase changing pressure from gaseous to supercritical CO<sup>2</sup> . At very low pressures (of about 2.5 to 3.5 MPa), the IFT vs. temperature isotherm crossover was reported by Hough et al. [17], Chun et al. [29], and Hebach et al. [72], but Hebach et al. [72] hypothesized that the observed crossover of the isotherms could be due to the use of pure component phase densities instead of saturated phase densities for CO<sup>2</sup> and water. Bikkina et al. [15] used saturated phase densities for their IFT data and did not observe the crossover point to a pressure as low

as 1.48 MPa, as shown in **Figure 6**. For pressures above ~13 MPa and temperatures above the critical temperature (i.e., supercritical state), no or insignificant effect of temperature on IFT was reported [15, 17, 29, 64, 65, 72]. Whereas, a decrease in IFT with temperature between 212 and 400°F and pressure up to 18,000 psia was reported by Shariat et al. [25]. It should be noted that the experimental temperatures used for Shariat et al. [25] data are much higher



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175

than others.

**Figure 6.** IFT isotherms for the CO<sup>2</sup>

**Figure 5.** Comparison of published IFT data for CO<sup>2</sup>

**Figure 5.** Comparison of published IFT data for CO<sup>2</sup> -water system at 298 K [15].

0.2 g/cc CO<sup>2</sup>

density (42° at 1.7 OH/nm<sup>2</sup>

systems. 0–3 M NaCl and CaCl<sup>2</sup>

174 Carbon Capture, Utilization and Sequestration

330 K and 20 MPa and reported CO<sup>2</sup>

brine [68].

**5. Interfacial tension data comparison**


of the placement of thermocouple away from the droplet.

ties instead of saturated phase densities for CO<sup>2</sup>

As shown in **Figure 5**, IFT sharply decreased with pressure when the CO<sup>2</sup>

near the phase changing pressure from gaseous to supercritical CO<sup>2</sup>

phobic surface, the reported CO<sup>2</sup>

nearly constant when the CO<sup>2</sup>

simulations IFT data for CO<sup>2</sup>

in 0.26 M CaCl<sup>2</sup>

IFT data for CO<sup>2</sup>

of CO<sup>2</sup>

the CO<sup>2</sup>

CO<sup>2</sup>

density lost its contact from the surface upon further increase in CO<sup>2</sup>

parameters for Si-O, O-H, O-Si-O, Si-O-Si, and Si-O-H groups to predict CAs for brine-CO<sup>2</sup>

insignificant within the conditions tested (7 and 9.6 MPa at 318 K and 10.9 MPa at 333 K).

Tenney and Cygan performed molecular dynamics simulations for brine-CO<sup>2</sup>

to 35° at 3.7–4.5 OH/nm<sup>2</sup>

tions, on fully hydroxylated silica surface with 9.4 OH/nm<sup>2</sup>

surfaces in the presence of water, NaCl, and CaCl<sup>2</sup>

and 10 MPa, McCaughan et al. [67] reported that the CA reduced with increasing silanol group

22.6° for water) agreed well with their experimental results (20–21°). Their results indicate that CA slightly increases (about 7–13°) with ionic strength (0–3 M), and the trend is similar for both monovalent and divalent ions. They also reported that CA dependence on pressure and temperature is

were 169° in water and 180° in both brines on the hydrophilic surface, whereas on the hydro-

There have been a significant number of experimental and simulation studies on the IFT data

Bennion, Bikkina et al., and Kravanja et al. used pendant drop method, whereas Chun et al. used capillary rise method [15, 20, 28, 29, 72]. The lowest IFT reported by Chun et al. [29] near the phase changing pressure was explained by Hebach et al. [72] as a potential consequence

Similarly, IFT vs. pressure trends were also observed at above critical temperature of CO<sup>2</sup>

rich phase, as shown in **Figure 6** [15]. Majority of the reported experimental and molecular

(of about 2.5 to 3.5 MPa), the IFT vs. temperature isotherm crossover was reported by Hough et al. [17], Chun et al. [29], and Hebach et al. [72], but Hebach et al. [72] hypothesized that the observed crossover of the isotherms could be due to the use of pure component phase densi-

phase densities for their IFT data and did not observe the crossover point to a pressure as low


is gaseous phase [15–17, 20, 24, 29, 64, 72]. The increase in IFT with temperature is higher


density. At 300 K


is gas and it becomes

. At very low pressures

and water. Bikkina et al. [15] used saturated


CAs


). Chen et al. [69] performed molecular simula-

brines were used in the study. The predicted static CAs (e.g.,

CAs for hydrophilic gibbsite and hydrophobic siloxane

CAs were 145° in water, 141° in 0.78 M NaCl brine, and 145°

is liquid. It should be noted that Hebach et al., Bachu and


brine solutions. The reported CO<sup>2</sup>

silanol group density, using force field

**Figure 6.** IFT isotherms for the CO<sup>2</sup> -water system at various pressures [15].

as 1.48 MPa, as shown in **Figure 6**. For pressures above ~13 MPa and temperatures above the critical temperature (i.e., supercritical state), no or insignificant effect of temperature on IFT was reported [15, 17, 29, 64, 65, 72]. Whereas, a decrease in IFT with temperature between 212 and 400°F and pressure up to 18,000 psia was reported by Shariat et al. [25]. It should be noted that the experimental temperatures used for Shariat et al. [25] data are much higher than others.

As shown in **Figure 7**, an invariant IFT vs. "aqueous and CO<sup>2</sup> phase density difference (Δρ)" irrespective of the pressure and temperature until a Δρ of about 600 kg/m3 and then a steep increase in IFT with Δρ was reported by Bikkina et al. [15]. Similar trends were reported by Chalbaud et al. for CO<sup>2</sup> -NaCl brine system [13].

Effect of N<sup>2</sup>

CO<sup>2</sup>

effect on IFT (CO<sup>2</sup>

38, 41] and CO<sup>2</sup>

a roughness value of 12 nm.

receding CA trends of quartz-CO<sup>2</sup>

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

5 and 10 vol.% Ar impurity in CO<sup>2</sup>


and pressure ranges of 40–90°C and 7.5–40 MPa.

**6. Contact angle data comparison**

surements were conducted at 13 MPa and 333 K. It was found that 50 mol% N<sup>2</sup>

also include measurements of water/brine droplet on substrate in CO<sup>2</sup>

that even static and dynamic CAs have been compared [27, 33].

face roughness on advancing and receding CA trends of calcite-CO<sup>2</sup>

studies reported on the influence of surface roughness on CA of mica-CO<sup>2</sup>


40.6 ± 3 mN/m) within experimental uncertainty. Kravanja et al. [28] measured IFT between

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

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

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

Al-Yaseri et al. thoroughly investigated the influence of surface roughness on advancing and

ness (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 sur-

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


bubble/droplet on substrate immersed in aqueous phase [34, 35, 41, 42, 54, 55].

stream containing Ar impurity and 23.26 g/L salinity brine and found that the presence of

contamination on IFT was studied by Al-Yaseri et al. [26]. About 5000 ppm NaCl

mixture were used as aqueous and gas phases, and the IFT mea-

Interfacial Tension and Contact Angle Data Relevant to Carbon Sequestration

stream has negligible effect on IFT within the temperature

/N<sup>2</sup>

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

has negligible

177

mixture-brine IFT of

[23, 26, 27, 30, 31, 33,



There has been a common agreement on the effect of salinity on IFT data (from experimental measurements and molecular simulations) of CO<sup>2</sup> -brine systems [13, 15, 20, 22, 42, 63–65]. 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 phase, is more than double for CaCl<sup>2</sup> solution compared to that of NaCl solution reported by Chalbaud et al. [13], and this increase was attributed to the presence of divalent cations in the case of CaCl<sup>2</sup> solution.

The influence of H<sup>2</sup> S, SO<sup>2</sup> , N<sup>2</sup> , and Ar contamination in CO<sup>2</sup> stream on IFT were investigated by Shah et al., Saraji et al., Al-Yaseri et al., and Kravanja et al., respectively [21, 26, 28, 42]. Shah et al. [21] conducted water-H<sup>2</sup> S IFT measurements up to 15 MPa and at 120°C and water-(30, 70 mol% H<sup>2</sup> S:CO<sup>2</sup> ) IFT measurements up to 15 MPa and at 77°C. Upon combined analyzation of their IFT data along with Chiquet et al. [18] water-CO<sup>2</sup> IFT data, they concluded a strong decrease of IFT with increase in H<sup>2</sup> S content in CO<sup>2</sup> . A significant linear decrease in IFT (i.e. from 29 mN/m in the case of pure CO<sup>2</sup> to 18 mN/m in the presence of 6 wt% SO<sup>2</sup> ) was reported by Saraji et al. [42]. The presence of weakly bounded surface complex between SO<sup>2</sup> and water molecules at the supercritical fluid/liquid interface was 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.

**Figure 7.** Effect of phase density difference on IFT for the CO<sup>2</sup> -water system at various temperatures [15].

Effect of N<sup>2</sup> contamination on IFT was studied by Al-Yaseri et al. [26]. 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 IFT measurements were conducted at 13 MPa and 333 K. It was found that 50 mol% N<sup>2</sup> has negligible effect on IFT (CO<sup>2</sup> -brine IFT of 38.7 ± 3.9 mN/m and 50:50 mol% CO<sup>2</sup> /N<sup>2</sup> mixture-brine IFT of 40.6 ± 3 mN/m) within experimental uncertainty. Kravanja et al. [28] measured IFT between CO<sup>2</sup> stream containing Ar impurity and 23.26 g/L salinity brine and found that the presence of 5 and 10 vol.% Ar impurity in CO<sup>2</sup> stream has negligible effect on IFT within the temperature and pressure ranges of 40–90°C and 7.5–40 MPa.
