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74 Ramin Moghadasi et al.
temperature at low pressures because light components (gas molecules) tend to vaporize at
high temperature. As pressure increases, however, liquid becomes denser at lower tempera-
tures—i.e., molecules in the liquid phase are packed more tightly and thus leave less room
for gas molecules to enter. Therefore, at high pressures, the solubility of gas in liquid may
increase with temperature because of the decrease in liquid density. This phenomenon was
shown in the plot of CO 2 solubility. The isothermal line of 200 F(94 C) crosses the line
of 140 F(60 C) at pressures above 3000 psia (20.7 MPa).”
Based on these statements and experimental results, they proposed the following
correlation:
h i
a 6
a 7
a 2
R s 5 1= a 1 γ T 1 a 3 T a 4 exp 2a 5 P 1 (3.5)
P
where R s is solubility in scf/bbl, T is temperature in F, P is pressure in psia, and γ is
22
specific gravity. The empirical constants a 1 through a 7 are 0.4934 3 10 , 0.928,
0.571 3 10 26 , 1.6428, 0.6763 3 10 23 , 781.334, and 20.2499, respectively. They used
the correlation for three different oil samples and have reported an average deviation of
5.9% for Cat Canyon oil, 7.6% for Wilmington oils, and 2% for Densmore oil.
Example 3.1: Consider the Chung et al. [40] correlation. Answer the following
questions:
a. What would happen if the pressure is increased to a very high value?
b. What would happen if the temperature is increased to a very high value?
Solution:
a. As the pressure is increasing to a very high value, the term a 6 =P would vanish.
Therefore the term expð2a 5 P 1 a 6 =PÞ is reduced to expð2a 5 PÞ. Putting a high
value in this remained term would also vanish the whole term a 3 T expð2a 5 PÞ.
a 4
As a result, the R s could be calculated by 1= a 1 γ T . This means that CO 2 solu-
a 7
a 2
½
bility is only dependent on temperature and specific gravity of the crude oil at
high pressures.
b. At very high temperatures, the term a 1 γ T a 7 is nearly equal to zero. What
a 2
remains is the term a 3 T expð2a 5 P 1 a 6 =PÞ, which would obviously result in
a 4
R s 5 0 at very high temperatures.
3.2.2.1.5 Emera and Sarma [41]
In 2007, they used genetic algorithm (GA) and proposed a new set of correlations.
Emera and Sarma [41] correlations are as follows:
• Dead oil:
a. For temperatures above critical temperature of CO 2 at any pressure:
