**3.3 Evaluation of antiwater blocking properties of OSSF**

## *3.3.1 Spontaneous imbibition property of cores*

As shown in **Figure 7**, water saturation of cores gradually increased with time. Obvious spontaneous imbibition and diffusion stages could also be seen. The increase in water saturation was dramatic at the spontaneous imbibition stage, but water

#### **Figure 4.**

**Figure 5.**

*Surface tension of 0.20 wt% solutions before and after aging (cooling down to room temperature, pH free).*

started to increase. Compared with distilled water, OSSF solution could achieve an additional damage rate reduction of 15%. The results suggest that the water blocking damage rate of the reservoir increased remarkably when the external liquids invaded into reservoir at the beginning. After reaching a certain water

saturation, the water blocking damage did not increase significantly.

*Performance Evaluation and Mechanism Study of a Silicone Hydrophobic Polymer…*

*DOI: http://dx.doi.org/10.5772/intechopen.90811*

*Water saturation (Sw) of artificial cores treated by 0.2% OSSF solution.*

*Water blocking damage rate (I) of artificial cores versus self-absorbed time (t).*

**Figure 8.**

**Figure 9.**

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**Figure 6.**

*Surface tension of 0.40 wt% solutions before and after aging (T = 25°C, pH free).*

**Figure 7.** *Water saturation (Sw) of artificial cores versus spontaneous imbibition time (t).*

saturation was compromised at the diffusion stage. Effective pores can imbibe the liquid by capillary force, whereas liquid accessing to unconnected pores only relies on diffusion from connected pores, which requires more time. Water saturation decreased from about 71–68% with a 0.20 wt% OSSF in the spontaneous imbibition stage. The spontaneous imbibition time then changed from about 33 to 28 min.

**Figure 8** shows the cores treated by 0.2% OSSF solution. Water saturation decreased to 56% and the saturation time decreased to 68 min in the spontaneous imbibition stage. These results indicate that the spontaneous imbibition rate and the amount of external liquid in a reservoir can easily be reduced.

#### *3.3.2 Water blocking damage rate of cores*

As shown in **Figure 9**, the water blocking damage rate of distilled water and OSSF solutions increased sharply at the beginning. However, after 20 min, it slowly *Performance Evaluation and Mechanism Study of a Silicone Hydrophobic Polymer… DOI: http://dx.doi.org/10.5772/intechopen.90811*

started to increase. Compared with distilled water, OSSF solution could achieve an additional damage rate reduction of 15%. The results suggest that the water blocking damage rate of the reservoir increased remarkably when the external liquids invaded into reservoir at the beginning. After reaching a certain water saturation, the water blocking damage did not increase significantly.

**Figure 8.** *Water saturation (Sw) of artificial cores treated by 0.2% OSSF solution.*

**Figure 9.** *Water blocking damage rate (I) of artificial cores versus self-absorbed time (t).*

saturation was compromised at the diffusion stage. Effective pores can imbibe the liquid by capillary force, whereas liquid accessing to unconnected pores only relies on

As shown in **Figure 9**, the water blocking damage rate of distilled water and OSSF solutions increased sharply at the beginning. However, after 20 min, it slowly

diffusion from connected pores, which requires more time. Water saturation decreased from about 71–68% with a 0.20 wt% OSSF in the spontaneous imbibition stage. The spontaneous imbibition time then changed from about 33 to 28 min. **Figure 8** shows the cores treated by 0.2% OSSF solution. Water saturation decreased to 56% and the saturation time decreased to 68 min in the spontaneous imbibition stage. These results indicate that the spontaneous imbibition rate and the

amount of external liquid in a reservoir can easily be reduced.

*Water saturation (Sw) of artificial cores versus spontaneous imbibition time (t).*

*Surface tension of 0.40 wt% solutions before and after aging (T = 25°C, pH free).*

*21st Century Surface Science - a Handbook*

*3.3.2 Water blocking damage rate of cores*

**Figure 6.**

**Figure 7.**

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#### *3.3.3 Permeability recovery of cores*

As shown in **Figure 10**, the permeability recovery of the cores gradually increases with flow-back PV. Meanwhile, the recovery rate gradually decreases. When gas pressure was 0.06 MPa and the flow-back PV is 20, the cores' permeability recovery changes from 7 to 77%. It is evident that the higher the displacing pressure, the higher the permeability recovery. A permeability recovery of 0.20% OSSF solution increased from about 8 to 93%; then, with the distilled water, the permeability recovery was 77%. Both increases were at 0.06 MPa and 20 PV. At 0.03 MPa and 20 PV, permeability recovery of 0.20% OSSF solution increased from about 7 to 86%, with the distilled water 67% by contrast. These results illustrate that the increase of flow-back volume and gas pressure can improve the permeability recovery and reduce the water blocking damage of cores. In addition, OSSF is beneficial to the permeability recovery of the reservoirs damaged by external fluids.

*Performance Evaluation and Mechanism Study of a Silicone Hydrophobic Polymer…*

*DOI: http://dx.doi.org/10.5772/intechopen.90811*

*Size and distribution of OSSF aggregate versus weight percentage (T = 25°C, free pH).*

**Figure 12.**

**Figure 13.**

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*Flow patterns of OSSF aggregate in the reservoir pores.*

**Figure 10.** *Pore volumes (PV) versus permeability recovery rate of artificial cores (D).*

**Figure 11.** *Gas flow-back volumes versus remaining water saturation (Sw) of artificial cores.*
