Page 382 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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362 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
To estimate binary diffusion coefficients for hydrocarbon
gases at low pressures, Eq. (8.59) and for nonhydrocar- where
bons Eq. (8.58) can be used. For liquid hydrocarbons at A = 37.34745 − 0.20611M + 141.1265SG − 637.727I 20
low pressure, diffusion coefficients at infinite dilution can − 6.757T + 6.98(T ) − 0.81(T ) ,
∗ 3
∗ 2
∗
be estimated from Eq. (8.60) or (8.61) and for the effect b b b
of concentration on binary diffusion coefficients Eq. (8.64) B =−15.5437 + 0.046603M − 42.8873SG + 211.6542I 20
∗ 3
∗ 2
should be used. For both liquids and gases at high pressures, + 1.676T − 1.8(T ) + 0.212(T ) ,
∗
b
b
b
Eq. (8.67) is highly recommended and Eq. (8.66) can be used T = (1.8T b − 459.67)/1.8
∗
as alternative method for diffusivity of a gas in oil under reser- b
voir conditions. When using Eq. (8.67) recommended meth- in which T b is the average boiling point in Kelvin, μ
ods for calculation of low-pressures properties must be used. is in cP, and parameter I should be determined at the
For multicomponent gas mixtures at low pressure, Eq. (8.68) same temperature as μ is desired. (Parameter I can be
and for liquids or gases at high pressures Eq. (8.69) is recom- determined as discussed for its use in Eq. (8.78).)
mended to calculate effective diffusion coefficients. Effect of For kerosene sample of Problem 8.2, calculate visco-
porous media on diffusion coefficient can be calculated from sity based on the above method and obtain the error.
Eqs. (8.70) and (8.74). Self-diffusion coefficients or when re- 8.4. Methane gas is dissolved in the kerosene sample of Prob-
fractive index is available, Eq. (8.78) can be used. lem 8.2, at 333 K (140 F) and 20.7 bar (300 psia). The
◦
Surface tension of pure compounds should be calculated mole fraction of methane is 0.08. For this fluid mix-
from Eq. (8.85) and defined mixtures from Eq. (8.86) with ture calculate density, viscosity, and thermal conductiv-
parachors given in Table 8.14 or Eq. (8.86) for n-alkanes. ity from appropriate methods. The experimental value
For undefined petroleum fraction surface tension can be of density is 5.224 kmol/m .
3
calculated from Eq. (8.90). For defined petroleum fractions 8.5. Estimate diffusion coefficient of methane in kerosene
(known PNA composition), Eq. (8.93) is recommended. For sample of Problem 8.4 from Eqs. (8.65)–(8.67).
coal liquid fractions Eq. (8.91) may be used. Equation (8.95) 8.6. Estimate thermal conductivity of N 2 at 600 F and 3750
◦
is recommended for calculation of IFT of water–hydrocarbon and 10 000 psia. Compare the result with values of 0.029
systems. For specific cases, recommended methods are dis- and 0.0365 Btu/ft · h · F as reported in the API-TDB [5].
◦
cussed in Section 8.6.2. 8.7. Consider an equimolar mixture of C 1 ,C 3 , and N 2 at 14
In addition to predictive methods, two methods for experi-
mental measurement of diffusion coefficient and surface ten- bar and 311 K. The binary diffusion coefficient of D C1–C3
−4
−4
2
cm /s, re-
and D C1–N2 are 88.3 × 10
and 187 × 10
sion are presented in Sections 8.5 and 8.6.1. Furthermore, spectively. The mixture density is 0.551 kmol/m . Esti-
3
the interrelationship among various transport properties, ef- mate the effective diffusion coefficient of methane in the
fects of porous media and concept of wettability, calculation mixture from Eq. (8.68) and compare it with the value
of capillary pressure and the role, and importance of interfa- calculated from Eqs. (8.67) and (8.69).
cial tension in enhanced oil recovery processes are discussed. 8.8. A petroleum fraction has boiling point and specific grav-
It is also shown that choice of characterization method could ity of 429 K and 0.761, respectively. The experimen-
have a significant impact on calculation of transport proper- tal value of surface tension at 25 C is 22.3 mN/m [59].
◦
ties of petroleum fractions.
Calculate the surface tension at this temperature from
the following methods and compare them against the
experimental value.
8.8 PROBLEMS a. Five different methods presented by Eqs. (8.88)–(8.92)
with estimated input parameters from the API-TDB
8.1. Pure methane gas is being displaced in a fluid mixture methods.
of C 1 , n-C 4 , and n-C 10 with composition of 41, 27, and b. Equation (8.93) with predicted PNA distribution.
32 mol%, respectively. Reported measured diffusion co- c. Fawcett’s method for parachor (Eq. 8.94).
efficient of pure methane in the fluid mixture under the d. Firoozabadi’s method for parachor.
conditions of 344 K and 300 bar is 1.01 × 10 −4 cm /s [9].
2
a. Calculate density and viscosity of fluid.
b. Estimate diffusion coefficient of methane from
Sigmund method (Eq. 8.65). REFERENCES
c. Estimate diffusion coefficient of methane from
Eq. 8.67. [1] Bird, R. B., Stewart, W. E., and Lightfoot, E. N., Transport
8.2. Hill and Lacy measured viscosity of a kerosene sample at Phenomena Processes, Wiley, New York, 1960; 2nd ed., 1999.
333 K and 1 atm as 1.245 mPa · s [51]. For this petroleum [2] Gallant, R. W. and Yaws, C. L., Physical Properties of
fraction, M = 167 and SG = 0.7837. Estimate the viscos- Hydrocarbons, Vol. 1, 2nd ed., Gulf Publishing, Houston, TX,
1992.
ity from two most suitable methods and compare with [3] Alberty, R. A. and Silbey, R. J., Physical Chemistry, 2nd ed.,
given experimental value. Wiley, New York, 1999.
8.3. Riazi and Otaibi [21] developed the following relation [4] Hirschfelder, O. J., Curtiss, C. F., and Bird, R. B., Molecular
for estimation of viscosity of liquid petroleum fractions Theory of Gases and Liquids, Wiley, New York, 1964.
based on Eq. (8.78): [5] Daubert, T. E. and Danner, R. P., Eds., API Technical Data
Book—Petroleum Refining, 6th ed., American Petroleum
1/μ = A + B/I Institute (API), Washington, DC, 1997.
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