Page 162 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

146 Gas Wettability of Reservoir Rock Surfaces with Porous Media

6
100%FC-1
80%FC-1
5 60%FC-1
40%FC-1
Expansion height/mm 3 2
20%FC-1
4
0%FC-1

1

0
0 2 4 6 8 10 12 14 16
Time/h
FIGURE 4.14
Expansion characteristic of gas-wetting clay.

mounted on the expansimeter. Distilled water was injected to measure the
expansion capacity by 16 hours. The result is displayed in Fig. 4.14.
From Fig. 4.14, it can be seen that as the concentration of gas-wetting alter-
ation agent increases, the expansion characteristic of montmorillonite weakens
gradually. When the concentration of gas-wetting alteration agent is 100%, the
maximum expansion height of montmorillonite is 0.83 mm after 16 hours.
The upper side and lower side of the crystal layers of montmorillonite are all
oxygen atoms. Every crystal layer is connected by intermolecular forces; hence,
the connection force is weak, and it is easy for water molecules to get between
crystal layers, causing lattice expansion. The expansion characteristic of
montmorillonite treated with gas-wetting alteration agent decreases greatly,
which is because the gas-wetting alteration agent forms a stable layer of gas-
wetting protection film on the surface of the montmorillonite grains. It is both
hydrophobic and oleophobic. It prevents water molecules from getting
between the crystal layers of the montmorillonite and the hydration expan-
sion. Correspondingly, it maintains the stability of the montmorillonite.

4.2.4.3 MICROSTRUCTURE ANALYSIS
4.2.4.3.1 Scanning Electron Microscopy and Energy
Spectrum Analysis
Montmorillonite samples were prepared before and after gas-wetting alteration
was conducted, and the surface energy spectrum was analyzed using a Quanta
200F field emission scanning electron microscope. The result is displayed in
Table 4.15.