Page 127 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Gas-wetting Alteration Agent and Gas-wetting CHAPTER 3 111

130 90

120 80
Contact angle/° 110 Contact angle/° 70
100
60
90
100°Aging/12h 50
100°Aging/12h
aging at room temperature/12h
80 40
aging at room temperature/12h
70 30
1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10%
FC-1 concentrations FC-1 concentrations
(A) (B)
FIGURE 3.19
Contact angles of distilled water (A) and n-hexadecane (B) on the surface of cores treated with a solution of gas-wetting
alteration agent of different concentrations.

When the core was treated with a solution that has 10% gas wetting alteration
agent and was treated at 100 C for 12 hours, the contact angle of distilled

water on its surface reaches 124.98 degrees, and that of n-hexadecane on its
surface is up to 84.69 degrees, indicating that the core surface treated with gas-
wetting alteration agent has changed into hydrophobic and oleophobic inter-
mediate gas-wetting.
The contact angles of distilled water and n-hexadecane on core surface are all
obviously increased after heat treatment at 100 C for 2 hours. The effect of

treating cores under high temperature by 2% gas-wetting alteration agent is
comparable to the effect of treating it with 10% gas-wetting alteration agent
before heat treatment. Therefore, a gas-wetting alteration agent with low con-
centration makes the core surface highly hydrophobic and oleophobic after

heat treatment at 100 C. This agent also has good heat stability, which is
largely because when the gas-wetting alteration agent is used to create a film
and is processed at high temperature on the core surface, the fluorine-
containing alkylon the film surface moves further toward the polymer-air
interface, and is enriched on the core surface, resulting in an increase in fluo-
rine atom content. The mechanism of the effect of high temperature aging dur-
ing the film-forming process of fluoro-copolymer is shown in Fig. 3.20. The
image of contact angle of water-phase and oil-phase on the core surface after
heat treatment at 100 C for 12 hours is shown in Fig. 3.21.

Owens’ two-liquid method was adopted to calculate the surface energy change
using contact angle data of water and oil phases on the artificial core surface,
before and after treatment. The results are shown in Fig. 3.22.
From Fig. 3.22, it can be seen that with the increase inconcentration of gas-
wetting alteration agent, the surface energy of the treated cores was obviously
reduced, and was further reduced after heat treatment. The gas-wetting alter-
ation agent was adsorbed on the core surface, and the fluorinated side chain