Page 108 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

92 Gas Wettability of Reservoir Rock Surfaces with Porous Media

Table 3.7 Effect of pH on Gas Wettability Alteration
pH Value 1.5 3 5 6.5 10 12
Contact angle ( ) Water 133 134 137 140 145 88

Oil 91 93 90 101 95 39

Table 3.8 Effect of Methanol on Gas Wettability Alteration of Core
Surface
Methanol Concentration (%) 0 1 3 5 7 10 15 25 40 50
Contact angle ( ) Water 142 140 140 145 145 142 144 138 73 56

Oil 101 101 104 100 100 97 97 90 48 42

It can be seen from Table 3.7 that when the treatment solution is acidic, gas
wettability of the rock sample is basically not affected, presenting obvious gas
wettability. When the liquid is weakly alkaline, gas wettability is still strong.
When the pH value of the solution is greater than 10, gas wettability weakens
rapidly. When the pH value is increased to 12, the rock sample’s surface shows
no gas wettability. It is concluded that this rock sample preparation method
for gas wettability still shows very good effects in acidic and weakly alkaline
environments. Therefore, measures to improve oil recovery, such as acidifica-
tion of alkaline flooding, can be carried out.

3.1.3.4 EFFECT OF ALCOHOL ON GAS WETTABILITY ALTERATION
OF ROCK SAMPLES
1. Effect of methyl alcohol on gas wettability alteration of rock samples
It can be seen from Table 3.8 that when the concentration of methanol in the
treatment solution is less than 25%, gas wettability of treated core surface is
relatively unchanged, and continues to present very strong gas wettability.
However, when the concentration is greater than 25%, gas wettability of the
treated core surface reduces rapidly until there is no gas wettability. Hence, the
existence of methanol with high concentration is unfavorable for gas wettabil-
ity alteration of cores.
2. Effect of ethanol on gas wettability alteration of rock samples
It can be seen from Table 3.9 that when the concentration of ethanol in treat-
ment solution is less than 20%, gas wettability of the treated core surface is
relatively unchanged, and continues to present very strong gas wettability.
However, when the concentration is greater than 20%, gas wettability of the
treated core surface is somewhat reduced. Hence, high concentration of etha-
nol also affects the gas wettability alteration of cores.