Page 106 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

90 Gas Wettability of Reservoir Rock Surfaces with Porous Media

Table 3.3 Effect of Ca 21 on Alteration of Gas Wettability
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Ca Concentration 0 1000 5000 10000 15000 20000 50000 100000
(mg/L)
Contact Brine 140 133 133 132 132 132 135 133
angle ( ) N-decane 93 69 84 91 89 88 96 96

Table 3.4 Effect of Mg 21 on Alteration of Gas Wettability
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Mg Concentration (mg/L) 0 1000 5000 10000 15000 20000 50000
Contact angle ( ) Brine 140 135 133 125 135 135 118

N-decane 93 80 79 78 95 95 95

2. Effect of Ca 21 on alteration of gas wettability
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Different concentrations of Ca were added to the treatment solution, and
the contact angle of the treated core surface to brine and n-decane was mea-
sured, as shown in Table 3.3.
It can be seen from Table 3.3 that when calcium ion concentration is
1000B10,000 mg/L, there is mild weakening of gas wettability; however, the
level of decrease is very small. When the concentration is greater than
10,000 mg/L, it has little effect on gas wettability. Hence, the existence of
Ca 21 has a very little effect on the alteration, of gas wettability of the core as
well.

3. Effect of Mg 21 on alteration of gas wettability
Different concentrations of Mg 21 were added to the treatment solution, and
the contact angle of the treated core surface to brine and n-decane was mea-
sured, as shown in Table 3.4.
It can be seen from Table 3.4 that when the concentration of magnesium ion
is 1000 mg/LB15,000 mg/L, there is a slight weakening of gas wettability.
However, the degree of weakening is very small. When the concentration
reaches 15,000 mg/L, gas wettability is affected a little and recovers somewhat.
When the concentration is 5,000 mg/L, gas wettability weakens to some extent.
However, the contact angles of core surface to oil and water are all larger than
90 degrees at this time. It is still intermediate gas wettability. Therefore, the
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existence of Mg weakens gas wettability of the cores.
31
4. Effect of Fe on gas wettability alteration
31
Different concentrations of Fe were added to the treatment solution, and the
contact angle of treated core surface to brine and n-decane was measured, as
shown in Table 3.5.