Page 92 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

76 Gas Wettability of Reservoir Rock Surfaces with Porous Media

θ waterðparaffinÞ . θ waterðplasticÞ . θ waterðglassÞ . θ waterðironÞ
And θ oilðparaffinÞ . θ oilðplasticÞ . θ oilðglassÞ . θ oilðironÞ .
Based on the Zisman theory, the smaller the surface energy of the matrix is,
the greater the contact angle of the liquid [3]. Hence the order of surface
energy of measuring matrix is: paraffin , plastic , glass , iron.
See Fig. 2.37 for gas-wetting parameters of various measuring matrices.
Fig. 2.37 shows that the order of gas-wetting ability of various measuring
matrix surfaces is: paraffin. plastic . glass . iron. And the surface of paraffin
shows preferential gas-wetting characteristics in water-paraffin-air system. The
wettability of matrix surface caused by air with respect to water is stronger
than that of the same matrix surface caused by air with respect to oil, which is
mainly because any increase in hydrophobicity results in stronger gas wettabil-
ity, and wettability of oil on the same matrix surface is stronger than water.

2.4.3.2 STUDY OF BUBBLE CAPTURE METHOD
The bubble capture method is adopted to evaluate gas wettability of various
measuring matrices. The experimental result is displayed in Fig. 2.38. Fig. 2.39

0.3 ζ gas–water Gas-wetting index Paraffin Plastic Glass Iron sheet
0.0
0.2
Measuring matrice
0.1 –0.2
ζ gas–water 0.0 Paraffin Plastic Glass Iron sheet ζ gas–water –0.4
–0.1
Gas-wetting index Gas-wetting index
–0.2 –0.6
–0.3
–0.8
–0.4
–0.5
–1.0
FIGURE 2.37
Gas-wetting parameter of various measuring matrices.

154.35
160 119.59 107.13 142.66 146.4 135.89 Gas contact angle in water
140
Contact angle (º) 120 70.53 100.23
Gas contact angle in oil
100
80
60
40
20
0
Paraffin Plastic Glass Iron sheet
Measuring matrice
FIGURE 2.38
Gas wettability evaluation of various matrices with bubble capture method.