Page 206 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

190 Gas Wettability of Reservoir Rock Surfaces with Porous Media

Table 5.3 Result of Gas Permeability After Displacement Experiment
Rock Contact Gas Permeability Gas Permeability After Permeability
2
Sample Angle of Before Displacement Displacement (10 23 µm ) Reduction (%)
2

Number Gas ( ) (10 23 µm )
0 1 138.4 1505.2 447.5 70.27
7 1 94.2 1455.0 756.4 48.01
15 1 69.0 1420.7 1100.2 22.56

Table 5.4 Effect of Gas Wettability on Displacement Characteristic of Gas-Displacing-Oil
Experiment Core Time When Oil Gas Breakthrough Saturation of Initial Contact

Number Number Appears (min) Pressure (MPa) Residual Oil (%) Angle of Gas ( )
No. 3 0 2 110.4 1.43 72.6 143.2
7 2 87.9 1.26 65.5 103.2
No. 4 0 2 123.1 1.42 73.0 143.2
15 2 68.7 1.09 43.7 77.3

experiment No. 2 is greater than that of core 7 1 parallel with core 0 1in
experiment No. 1. The water fluidity difference in the two cores that are paral-
lel is greater. It leads to water appearing earlier in core 7 1 compared to core
15 1, and less gas breakthrough pressure. The time when water appears in
core 0 1 in experiment No. 2 is extended, but the gas breakthrough pressure
does not change. This is due to the unchanged wettability of core 0 1. During
the experiment, when the gas preferentially breaks through the cores, water
won’t be generated any longer or won’t be generated at all.

The experimental result of gas permeability measurement when every parallel
experiment group is completed is as shown in Table 5.3.
It can be seen from Table 5.3 that when gas breaks through the core saturated
with oil, gas permeability of cores with different gas wettability is reduced by
different degrees, compared to dry cores before water saturation. The stronger
the gas wettability, the less the permeability reduces. This is due to stronger
gas wettability when gas-displacing-water process is completed. Therefore, the
saturation of residual water of cores is low and recovery value of gas perme-
ability is large.

5.3.2.2 DISPLACEMENT EXPERIMENT OF CORES WITH DIFFERENT GAS
WETTABILITY IN GAS/OIL SYSTEM
The effect of gas wettability on the time when oil is generated, gas break-
through pressure, and saturation of residual oil during the gas-displacing-oil
process, is as shown in Table 5.4.