**6. Improving foam stability using viscosifiers**

The addition of thickeners such as polymers or viscoelastic surfactant (VES) to CO2 foam improves foam stability by increasing lamella viscosity that delays

**Figure 13.**

*CT scan scans for Boise and Berea cores during the dual-core flood experiment after oil saturation, waterflooding, and foam-flooding stages.*

**137**

**Figure 14.**

*CO2 Foam for Enhanced Oil Recovery Applications DOI: http://dx.doi.org/10.5772/intechopen.89301*

[23, 33, 39, 40].

(OOIP).

flooding.

50–100 × 104

free foam system.

the lamella drainage effect at high temperature and in contact with crude oils

A dual coreflood experiment was conducted by Ibrahim and Nasr-El-Din [23, 24] to investigate the divergent ability of VES-stabilized foam in heterogeneous formations (with permeability contrast of 700/100). The VES was able to increase the foam stability and improve the sweep efficiency. The oil recovery after the waterflooding stage was 19 and 55% from the low and the high-permeability cores, respectively. Low sweep efficiency in the low-permeability cores was found where the residual oil saturation was 36 vol% compared to 31 vol% in the high-permeability core. When injecting VES into the foam system, the sweep efficiency improved, and the residual oil saturation decreased to 23 and 27 vol% in the low- and the high-permeability cores, respectively. The total oil recovery after foam injection was found to be 50 and 62 vol% of the original oil in place

**Figure 13** shows oil saturation distribution along the two cores after the foam-flooding stage compared to the oil-saturated and the waterflooded cases. For the high-permeability core, most of the oil was produced during waterflooding, and the recovery factor increased only by 10% after foam flooding. The slight change in distribution of the red areas in **Figure 13** indicates oil recovery from the waterflooded and the foam-flooded cases. In the case of low-permeability core, most of the reduction in the red color distribution happened after foam

**Figure 14** shows the results of using polymers as a thickener to improve the foam stability [41]. Wei et al. [41] used xanthan gum (molecular weight of

foam system at 90°*C* and 1450 psi. As the polymer concentration increases, the liquid phase viscosity increases. As a result, lamella drainage decreases, and foam-stability half-life increases. However, an increase in polymer concentration also increases the surface-tension forces and thus decreases the system foamability. Stable foam with a higher half-life increases the apparent viscosity for the displacing fluid that improves the sweep efficiency. The oil recovery for the polymer-foam system was 43.2%, compared to 21.8% in the case of the polymer-

*Effect of polymer concentration on the generated foam volume and its half-life.*

) to improve the foam stability for a sulfobetaine-based surfactant

*Foams - Emerging Technologies*

**6. Improving foam stability using viscosifiers**

The addition of thickeners such as polymers or viscoelastic surfactant (VES) to CO2 foam improves foam stability by increasing lamella viscosity that delays

*CT scan scans for Boise and Berea cores during the dual-core flood experiment after oil saturation,* 

**136**

**Figure 13.**

*waterflooding, and foam-flooding stages.*

the lamella drainage effect at high temperature and in contact with crude oils [23, 33, 39, 40].

A dual coreflood experiment was conducted by Ibrahim and Nasr-El-Din [23, 24] to investigate the divergent ability of VES-stabilized foam in heterogeneous formations (with permeability contrast of 700/100). The VES was able to increase the foam stability and improve the sweep efficiency. The oil recovery after the waterflooding stage was 19 and 55% from the low and the high-permeability cores, respectively. Low sweep efficiency in the low-permeability cores was found where the residual oil saturation was 36 vol% compared to 31 vol% in the high-permeability core. When injecting VES into the foam system, the sweep efficiency improved, and the residual oil saturation decreased to 23 and 27 vol% in the low- and the high-permeability cores, respectively. The total oil recovery after foam injection was found to be 50 and 62 vol% of the original oil in place (OOIP).

**Figure 13** shows oil saturation distribution along the two cores after the foam-flooding stage compared to the oil-saturated and the waterflooded cases. For the high-permeability core, most of the oil was produced during waterflooding, and the recovery factor increased only by 10% after foam flooding. The slight change in distribution of the red areas in **Figure 13** indicates oil recovery from the waterflooded and the foam-flooded cases. In the case of low-permeability core, most of the reduction in the red color distribution happened after foam flooding.

**Figure 14** shows the results of using polymers as a thickener to improve the foam stability [41]. Wei et al. [41] used xanthan gum (molecular weight of 50–100 × 104 ) to improve the foam stability for a sulfobetaine-based surfactant foam system at 90°*C* and 1450 psi. As the polymer concentration increases, the liquid phase viscosity increases. As a result, lamella drainage decreases, and foam-stability half-life increases. However, an increase in polymer concentration also increases the surface-tension forces and thus decreases the system foamability. Stable foam with a higher half-life increases the apparent viscosity for the displacing fluid that improves the sweep efficiency. The oil recovery for the polymer-foam system was 43.2%, compared to 21.8% in the case of the polymerfree foam system.

**Figure 14.** *Effect of polymer concentration on the generated foam volume and its half-life.*
