Page 63 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Evaluation Methods and Influencing Factors CHAPTER 2 47

25 0 mg/L
20 mg/L
30 mg/L
20 80 mg/L
100 mg/L
300 mg/L
H 2 /(cm) 2 15 500 mg/L
1000 mg/L
10 3000 mg/L
5000 mg/L
10000 mg/L
5

0
0 150 300 450 600 750 900 1050 1200 1350
t/s
FIGURE 2.12
Relation of self-suction height and time of water in quartz sand treated with CTAB.

Table 2.4 Contact Angle of Surface of Quartz Sand Treated With CTAB, to Water
CTAB Mass Slope θ ( ) R 2

Concentration (mg/L)
0 0.2925 0 0.9893
20 0.0500 80 0.9966
30 0.0366 83 0.9979
80 0.0067 88 0.9855
100 0.0045 89 0.9886
300 0.0505 80 0.9976
500 0.0654 77 0.9985
1000 0.0873 73 0.9973
3000 0.0878 72 0.9927
5000 0.1290 63 0.9842
10000 0.1170 66 0.9992

0 degree. Table 2.4 shows that when the concentration of CTAB is lower
(20 100 mg/L), CTAB has monolayer adsorption. The surface of quartz sand
can be translated into a water-wet one, the contact angle increases with
increasing concentration and water wettability becomes weaker. Intermediate-
wetting is achieved when the contact angle reaches 89 degrees and the
concentration of CTAB is 100 mg/L, with the continuous increase in CTAB con-
centration. When it reaches critical micellar concentration close to 300 mg/L, the
adsorption on solid surface changes from monolayer to bilayer adsorption. At
this time, the contact angle begins to decrease again with the increase in CTAB
concentration, and wettability changes from intermediate-wet to water-wet.

The same method is used to treat quartz sand with FC911 of various concen-
trations, and the contact angle of the surface of quartz sand processed with