# Flow Dynamics of Sulfate-Modified Water/Polymer Flooding in Micromodels with Modified Wettability
## 3 Results and Discussion
### Comparison of Micromodel Flood and Bentheimer Core Flood  
Comparisons of secondary mode brine floods in oil-wet artificial structure micromodel and Bentheimer core plugs are described in Figure 23. A detailed description of core flooding recovery mechanisms and pressure profiles are described in previous work [10]. In Figure 23, MM represents the recovery factors of micromodel, while CF represents the recovery factors of core flood and Difference represents the difference in recovery factors between both flooding. It is observed that brine flood of SSW and SSW-Na produced almost the same recovery factors (in CF and MM), with a difference of 1.89% for SSW and 0.37% for SSW-Na. The difference for SSW+2 SO4\({}^{2-}\) is significant, with a 10.66% recovery factor. Sulfate-modified produced a higher oil recovery through core plugs as compared to the micromodel. As previously discussed, wettability alteration (rock-fluid interaction) and IFV (fluid-fluid interaction) are the main recovery mechanisms for effective sulfate-modified water. It is believed that the IFV concept only worked in micromodel, resulting in the additional recovery of 2.35%. However, the wettability alteration did not happen, because of the strong adsorbed hydrophobic chemical layer at the matrix to make it oil-wet. Ionic activity because of sulfate-modified water is not strong enough to destroy the established oil-wet layer at the matrix. Furthermore, it is also believed  
Figure 22: Oil recovery and pressure drop versus PV injected for water-wet real structure micromodel. Polymer (equal to the oil viscosity) flooding in tertiary mode after the SSW+2 SO4\({}^{2-}\)/SSW brine flood in secondary mode. that the mechanism of IFV in micromodel is not strong enough as compared to the mechanism in the core flood. The reason is the availability of multiple flow paths (k\({}_{\text{x}}\), k\({}_{\text{y}}\), k\({}_{\text{z}}\)) in the core plug for easier oil ganglia movement. While on the other hand, in the micromodel, there is restricted two-way permeability for fluid flow and limited to flow channels. Looking at the difference between SSW injection and SSW+2 SO4\({}^{2-}\), a higher oil recovery of SSW+2 SO4\({}^{2-}\) is observed for both approaches. Sulfate-modified water worked much better in the core plug compared to the micromodel, due to a strong rock-fluids interaction. Table 13 represents the overall comparison between both types of micromodels and the core flood experiments used for this study. As presented in Table 13, SSW+2 SO4\({}^{2-}\) produced higher oil recovery in oil-wet MM and CF, and in complex-wet MM. Further, we can also see that SSW+2 SO4\({}^{2-}\) could not produce extra oil, as compared to SSW flooding through both water-wet MM (artificial structure and real structure). This comparison justifies that an oil-wet or mixed-wet reservoir system is essential for fluid-fluid and rock-fluid interaction to contribute extra oil recovery. The oil recovery difference between SSW+2 SO4\({}^{2-}\) and SSW flooding in oil-wet core plug is clear because of the strong rock-fluid interaction, which resulted in the local wettability alteration. Nevertheless, this rock-fluid interaction could not occur in micromodels, and difference in oil recovery between SSW+2 SO4\({}^{2-}\) and SSW flooding is smaller.