Page 49 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Evaluation Methods and Influencing Factors CHAPTER 2 33

I AðoÞ 5 ΔS oð5Þ =½ΔS oð5Þ 1 ΔS oð6Þ Š (2.2)

I AðwÞ —Amott index of water.
I AðoÞ —Amott index of oil.
ΔS wð3Þ —Change in water saturation during step 3 in Fig. 2.1.
ΔS wð3Þ —Change in water saturation during step 4 in Fig. 2.1.
ΔS wð3Þ —Change in oil saturation during step 5 in Fig. 2.1.
ΔS wð3Þ —Change in oil saturation during step 6 in Fig. 2.1.
In most cases, if any one Amott index ratio is zero, the result is easy to explain.
If both ratios are positive, the difference of them is taken as the wettability
index in Amott method. Measurement of wettability index through Amott
method is displayed in Fig. 2.2.

(2.3)
I AH 5 I AðwÞ 2 I AðoÞ
In the equation, I AH —is the comprehensive wettability index, Amott-Harvey
index;
The Amott method is used to measure a wide range of values from strongly
water-wet to strongly oil-wet. The values and boundaries are clearly defined,
and the measured results are close to the actual situation of oil and gas

FIGURE 2.1
Experimental procedure of Amott index method.

FIGURE 2.2
Evaluating wettability index using Amott method.