Page 87 - Fundamentals of Enhanced Oil and Gas Recovery

75
Enhanced Oil Recovery Using CO 2

mol 0:6474 0:25656

CO 2 solubility 5 2:238 2 0:33y 1 2:23y 2 4:8y (3.6)
mol

where y 5 γ T 0:8 exp 1 . For this correlation, the CO 2 solubility at P b (bubble
P s MW
point pressure equal to 1 atm for the dead oil case) is taken to be equal to zero.
b. For temperatures below critical temperatures of CO 2 at pressures under lique-
faction pressure of CO 2 :

mol 2 3 4
CO 2 solubility 5 0:033 2 1:14y 2 0:7716y 1 0:217y 2 0:2183y (3.7)
mol

where y 5 γ P s exp 1 .
P liq MW
In Eqs. (3.6) and (3.7), γ is the oil-specific gravity (oil density at 15.6 C), T is the

temperature ( F), P s is the saturation pressure (psi), P liq is the CO 2 liquefaction pres-
sure at the specified temperature (psi), and MW is the oil molecular weight (g/mol).
For accuracy evaluation, they examined the model with those data of Simon and
Graue [37], Mehrotra and Svrcek [39], and Chung et al. [40].
Emera and Sarma also conducted a sensitivity analysis for the factors that affect
CO 2 solubility in dead oil. They found that the GA-based CO 2 solubility correlation
for the dead oil depends, primarily, on the saturation pressure and temperature. Also,
it depends to a lesser degree on the oil-specific gravity and oil molecular weight.
• Live oil:
a. In case of gaseous CO 2 , for temperatures greater than CO 2 critical temperature
(T c,CO2 ) at all pressures, and for temperatures less than T c,CO2 at pressures less
than the CO 2 liquefaction pressure, CO 2 solubility can be calculated by the
following correlation:
mol

CO 2 solubility 5 1:748 2 0:5632y 1 3:273y 0:704 2 4:3y 0:4425 (3.8)
mol
1
1:125 expðÞ

MW
where y 5 γ 0:006897 3 ð 1:8T132Þ . For this correlation, it is consid-
P s 2P b
ered that the CO 2 solubility at P b is equal to zero.
b. In case of liquid CO 2 , for temperatures less than T c,CO2 and pressures greater
than CO 2 liquefaction pressure, they suggested the same correlation used for the
solubility in the dead oil (as given in Eq. 3.7) can also be used for the live oil.
For accuracy evaluation, they examined the model with those data of Simon and
Graue [37].
They also performed a sensitivity analysis of the factors affecting CO 2 solubility in
live oil. As they compared the results of sensitivity analysis for the live and deal oil,
they found that the saturation pressure effect on the CO 2 solubility in live oil is higher
than that in the dead oil. The temperature effect, on the other hand, is lower in the
live oil case.