Page 188 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

172 Gas Wettability of Reservoir Rock Surfaces with Porous Media

(A) (B)

(C)
FIGURE 5.7
Front shape of gas-displacing-water in capillaries having different gas wettability. (A) Nongas-wetting (convexity, θ gas 5 154.02
degrees), (B) nongas-wetting (convexity, θ gas 5 132.78 degrees), (C) nongas-wetting (convexity, θ gas 5 127.58 degrees).

It can be seen from Fig. 5.7 that in capillaries having different gas wettability,
the front has different shapes, and the advancing angle θ gas gradually reduces
as gas wettability increases. Under nongas-wetting conditions, as advancing
angle θ gas decreases, the fluidity of water becomes stronger and the flow resis-
tance of gas decreases. When water-blocking appears around the walls of a gas
reservoir or condensed gas reservoir, a gas-wetting alteration material is used
to reduce or relieve the water-locking effect and recover or maintain the capac-
ity of the gas well.

5.1.3 Oil-Displacing-Gas in Capillaries
5.1.3.1 EXPERIMENT METHOD
Gas-wetting alteration agent solutions of 0.1%, 2%, and 10% concentrations
were used to process quartz slides and inner walls of the quartz capillary,
made of the same material. After that, the gas wettability of slide surface and
inner wall surface of capillary changes. The gas wettability of the slide surface
having different gas wettability is evaluated using the bubble capture method
in oil. The gas wettability of the slide surface is characteristic of the gas wetta-
bility of the inner wall surface of the capillaries, treated by gas-wetting alter-
ation agent solution of same concentration. Under quasistatic conditions
(oil-displacing-gas speed is 0.3 mL/h), a gas-displacing-oil micro experiment is
conducted in single-straight capillaries having different gas wettability. During
the experiment, air is taken as the gas phase and neutral kerosene dyed with a
little Sudan Red is taken as the oil phase. During the displacement process,