Page 73 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Evaluation Methods and Influencing Factors CHAPTER 2 57

FIGURE 2.22
Stretch phenomenon of liquid drops and bubbles on solid surface. (A) Liquid drops; (B) bubbles.

Table 2.8 Relationship Between Gas Wetting Angle and Zonyl8740 Concentration in Oil
(Water) Phase
Zonyl8740 Concentration (%) 0.01 0.1 0.5 1.0 1.5 4.0 8.0 10.0

Gas contact angle in water θ gas2water ( ) 168.72 135.5 134.2 133.8 132.9 131.4 126.3 125.1
Gas contact angle in neutral kerosene 171.71 138.0 136.7 136.0 134.2 132.5 129.8 127.6
θ gas2neytralkerosene ( )

the bubble and solid interface and three points on the outer contour of the cir-
cle. The image is then automatically processed by a computer software using a
circle fitting model before finally determining the contact angle.

2.3.2.2.3 Experimental Result and Discussion
In distilled water (neutral kerosene), the bubble capture method is used to
measure the gas contact angle and study the change rule of gas wettability
with varying Zonyl8740 concentrations. From the experiment, it was found
that when air bubbles make contact with the solid interface, a stretching phe-
nomenon exists between the air bubbles and solid interface, which is similar
to the stretch formed between liquid drops and the solid surface by sessile
drop method in air (see Fig. 2.22). It indicates that an acting force exists
between the air bubbles and solid interface with gas wettability.

In the experiment, neutral kerosene is the liquid phase and the gas contact angle
of bubbles on the surface of the glass slide is noted as θ gas2neytralkerosene . When dis-
tilled water is the liquid phase, the gas contact angle of bubbles on the surface
of glass slide is noted as θ gas2water . The relationship among θ gas2neytralkerosene ,
θ gas2water , and Zonyl8740 concentration is displayed in Table 2.8.

From Table 2.8, it can be seen that θ gas2neytralkerosene , θ gas2water for the glass slide
treated with Zonyl8740 of the same concentration. Furthermore, gas contact
angle θ gas2water ðθ gas2neytralkerosene Þ gradually decreases as Zonyl8740 concentra-
tion increases and gas wettability strengthens. At the same time, it was found
that gas wettability of the glass slide surface in water, treated with Zonyl8740
solution of the same concentration, is greater than that in oil. It illustrates that