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PETROLEUM SCIENCE & ENGINEERING
ELSEVIER Journal of Petroleum Science and Engineering 13 ( 1995) 219-232
Assessment of the PVT correlations for predicting the properties of Kuwaiti crude oils
Adel M. Elsharkawy, Ahmed A. Elgibaly, Abbas A. Alikhan Petroleum Engineering Department, Kuwait University, P.O. Box 5969 &fat 13060, Kuwait
Received 30 September 1994; accepted 8 March 1995
Abstract
Several correlations have been proposed for determining PVT properties. Limitations concerning the validity of these corre-
lations for different types of hydrocarbon systems, accuracy, range of applicability, corrections for non-hydrocarbons contents, etc., have been controversial.
Because crude oils from different regions have different properties, it is recommended to assess the accuracy of the available
correlations. The present study is concerned with the assessment of these correlations for a variety of oils from Kuwaiti fields. The study
evaluated recently developed correlations in the Middle East region and the Arabian Gulf as well as those most often used. The limitations of these correlations have been analyzed. Forty-four individual crude oil samples from Kuwaiti oil fields were used
in this study. Corrections due to the presence of non-hydrocarbon gases, adjustment to oil composition, and correction of gas gravity to common separation conditions were taken into consideration. It was found that Standing’s correlation showed the best accuracy for predicting the bubble-point pressure among all others, though such accuracy is beyond desirable engineering limits.
All the correlations examined in the present study showed a comparable accuracy in predicting OFVF at the bubble point with
Al-Marhoun’s correlation having the least deviation.
1. Introduction
The accurate determination of the PVT properties of
the reservoir fluid, such as bubblepoint pressure, solu-
tion GOR and oil FVF, is necessary for the formation
evaluation of hydrocarbon reserves, reservoir perform-
ance, production operations and the design of produc-
tion facilities. Although these PVT properties can be
measured in the laboratory using collected bottom-hole
samples, it may occasionally be required to make pre- dictions with only data on reservoir pressure,
temperature, gas gravity and oil API gravity available.
Several correlations have been developed in the lit-
erature to estimate reservoir fluid properties. The most
0920.4105/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDlO920-4105(9S)OOO12-7
commonly used correlations are those given by Stand-
ing (1947, 1962, 1977). Standing’s correlations are based on solution gas-
oil ratio, gas gravity, oil API gravity and reservoir tem- perature. Twenty-two different crude oil and gas mixtures from California were used in developing his
correlation. He reported an average relative error of
4.8% for the bubblepoint pressure and an average rel-
ative error of 1.7% for the formation volume factor.
The ranges of the data used in developing Standing’s correlation are given in Table 1.
Lasater ( 1958) developed a correlation for the bub- blepoint pressure based on Henry’s law. He correlated mole fraction of gas in solution to a bubblepoint pres- sure factor. Lasater’s correlation is based on I 37 inde-
220 A.M. Elsharkawy et al. /Journal oj’Petroleum Science and Engineering 13 (1995) 219-232
pendent crude oil and gas mixtures from Canada, western and Mid-Continental US and South America.
Lasater reported an average error of 3.8% for his cor- relation. The ranges of data used in Lasater’s correla-
tion are also given in Table 1.
Vasquez and Beggs ( 1980) developed a PVT cor- relation based on 600 PVT laboratory analyses from
different oil fields representing a wide variety of loca- tions in the world. Their correlation is unique in cov- ering a wide range of crude oils with different physical
and chemical characters. This, in the meantime, repre- sents a weakness in the Vasquez and Beggs correlation because the composition of crude oil (classified as par-
affinic, naphthenic or aromatic) and the concentration
of non-hydrocarbon gases vary with each location. Fur-
thermore, they found that separation conditions affect
gas gravity which is a strong correlating parameter in their correlation. For this reason, they recommended
adjusting the gas gravity to a separator pressure of 100 psi. Vasquez and Beggs presented two correlations;
one for crudes having API gravity higher than 30 and another for crudes having API gravity equal or less than
30. Their correlation has an average error of 4.7% for the formation volume factor. It is important to note that
they reported the average temperature rather than the
temperature range used in developing their correlation.
Glaso ( 1980) developed correlations for calculating
the bubblepoint pressure and the oil formation volume factor, OFVF. A total of 45 oil samples mostly from
the North Sea region were used in his correlation. He
presented an adjustment to the API gravity term when his correlation is used with oils of different composi-
tions. The adjustment of API gravity is a function of residual oil gravity and dead oil viscosity from a dif- ferential test. Glaso reported that his correlations give an average error of 1.28% for bubblepoint pressure
and - 0.43% for OFVF. Al-Marhoun ( 1988, , 1992) developed correlations
for calculating the bubblepoint pressure and OFVF. He
used 69 bottom-hole samples collected from the Middle East. As shown in Table I, Al-Marhoun’s correlations have the advantage of covering a wide range of non- hydrocarbon gases. He reported an average error of 0.03% for bubblepoint pressure and - 0.01% for the oil formation volume factor.
Dokla and Osman ( 1992) presented correlations for bubblepoint pressure and oil formation volume factor. Fifty data points from UAE reservoirs were used in
their correlation. They showed an average error of
0.45% for bubblepoint pressure and 0.023% for oil formation volume factor.
Labedi ( 1990) developed correlations for oil for-
mation volume factor, density and compressibility. His
correlations are based on pressure and temperature of
the first stage separator, total GOR, gas gravity, oil API and reservoir temperature. Labedi’s correlation for
OFVF is based on 128 oil samples collected from Afri- can countries, mostly from Libya. He reported an aver-
age error of 0.003% and a standard deviation of 2.96% for the OFVF.
Ostermann et al. (1983) evaluated the Standing,
Lasater, Vasquez and Beggs, and Glass correlations for their accuracy in predicting PVT properties for the
“Alaskan crudes”. They used PVT results of eight
samples from flash and differential separation in their
evaluation. Ostermann et al. found that Glaso’s corre- lation for bubblepoint pressure and Standing’s corre- lation for oil FVF are the most accurate.
Suttan and Farshad (1990) studied Standing’s and Glaso’s correlations for their ranges of accuracy in esti- mating the PVT correlations of the “Gulf of Mexico
crudes” . They used 3 1 different crude oil/gas systems
and adjusted differential PVT data to represent flash data for the correlations used in their study. Suttan and
Farshad found that Glaso’s correlation is better than
Standing’s correlation but the accuracy is undesirable.
The presence of non-hydrocarbon gas in surface-
produced gas has a significant effect on the prediction of bubblepoint pressure from PVTcorrelations. Lasater
reported that the estimated bubblepoint pressure decreases as the CO, content increases, while Glase, reported the opposite effect. Jacobson (1967) and Glaso found that bubblepoint pressure increases with
increasing N2 content but decreases with increasing H,S content.
Although each of the afored-mentioned correlations was developed for crude oils of a specific region, some
authors claim that their correlations adequately fit ran- dom PVT data and can be applied to crude oils from other geological areas. Most engineers prefer Stan- ding’s correlation for low API crudes and Lasater’s correlation for high API crudes.
Glaso tried to extend his correlation to oils with different paraffinity. His correlation became of limited use because residual API gravity and dead oil viscosity from differential tests may not be available. It is impor-
A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 219-232 221
Table 1 Data ranges for published PVT correlations and present study
Standing
(1947)
Lasater
(1958)
Vasquez and Beggs
( 1980)
YAW 5 30 YAM ’ 30
Glaso
( 1980)
Al-Marhoun Dokla and Labedi Present study (1988) Osman (1990)
(1992)
Bubblepoint 130-7000 48-5680 154572 156055 165-7142 130-3573 590-4640 3x7-4375 pressure (psia)
Bubblepoint 908-48,800 335-39,670 105-71,931 105-42,288 1152- 908-24.954 4 120- 2:! 14-30555
pressure (Kpa) 49,880 32,406
Temperature (“F) 100-258 82-272 162” 180 80-280 74240 190-275 loo-306 130-250
Temperature (“C) 38-125 28-133 72” 82” 27-138 23-l 15 88-135 38-152 55-121
FVF, RBISTB 1.024-2.15 - 1.042-1.545 1.028-2.226 1.032-2.588 1.032-1.997 1.216-2.493 1.040- 1,057-l .770
(m3/Stdm7) 3.092
Solution GOR 20- 1425 3-2905 O-831 O-2199 90-2637 26-1602 181-2266 13-3533 34-1400
(SCF/STB)
Solution GOR 3-254 O-517 O-148 O-392 16470 5-285 32-403 2-680 6-250
(m’/Stdm’)
Tank-oil gravity 16.5-63.8 17.9-51.1 15.3-30.0 30.6-59.5 22.3-48.1 19.40-44.6 2840.3 32.2-48 20-45
(“API)
Gas gravity 0.59-0.95 0.574-1.223 0.511-1.351 0.530-1.259 0,650-l ,276 0.752-1.367 0.798-1.290 0.698- 0.663- 1.064
(air= 1) I.473
CO2 in surface < 1% 0 _ _ 0.00-16.38 0.37-8.9 - 0.0-6.9
gases (mol%)
Nz in surface 0 0 0.00-3.89 0.1-1.85 - 0.0-4.4
gases (mol%)
H2S in surface 0 0 _ 0.00-16.13 O-6.02 - 0.0-2.44
gases (mol%)
“Average temperature
-: Unavailable data.
tant to mention that the number of separation stages
and conditions affect the input data into any PVT cor- relation.
Before a given PVT correlation is selected for use in
reservoir calculations, it is necessary to examine the
range of data, covered by such a correlation, the com- position of oil and gas used in developing the correla- tion, and compare these data with the reservoir under
study. The objective of the present study is to examine the
PVT correlations available in the literature, especially the recently developed correlations for oils in the Mid-
dle East, to assess their accuracy for predicting the PVT properties of the Kuwaiti crudes.
2. The present study
Seventy-four measured PVT data points, represent- ing 44 different crude oil/gas systems from Kuwaiti
oil fields, were utilized in the present study. The bub-
blepoint pressure, bubblepoint oil FVF, solution GOR,
gas gravity and oil API were measured by flash and
differential separation for 30 crude oil/gas mixtures.
PVTdata for the remaining 14 mixtures were measured
by differential separation only, Also, dead oil viscosity
by differential separation and concentration of non-
hydrocarbon gases for the 44 crude oil/gas systems,
were available in the present study (see Table 4 in
Appendix D) . It is worthy to note that these mixtures
represent samples from fields in the west, south and
southeast of Kuwait.
Crude oils from the west Kuwaiti field used in this
study are characterized by high API gravity (37-43”).
The surface gas contains O-4.4% N,, 26.9% CO, and
O-2.5% H,S. South and southeast Kuwaiti fields are
characterized by medium gravity crude oils (2O-
35”API), and surface gas contains very small amounts
of N2 and COZ, O-l% and o-0.68%, respectively, with
A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (199.5’) 219-232
1 10 100 1000
Flash GOR, m3/Std ,3
Fig, 1, Flash versus differential GOR for Kuwaiti crudes.
1.800
1.600
Bobdaa 1.057
1.000 1.200 1.400 1.600 1.800 2.000
Flash OFVF, m3/Std m3
Fig. 2. Flash versus differential OFVF for Kuwaiti crudes.
Table 2
Statistical accuracy of bubblepoint pressure calculations for the Kuwaiti crude oils
Standing Lasater Vasquez-Beggs Glaso Dokla-Osman Al-Marhoun
Average error (%) 7.032 1.32 15.21 27.52 -6.3 9.96
Average absolute error (%) 10.85 14.01 16.4 27.66 16.86 22.64 Standard deviation 14.66 17.96 21.87 35.02 20.43 28.42
A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering I3 (1995) 219-232 223
Experimental bubblepoint pressure, Kpa
0 YXM IWOO ,5wo 2woo 25wo 300 35~
Experimental Bubblepoint Pressure, psi
Fig. 3. Crossplot for bubblepoint pressure.
224 A.M. Elsharkawy et al. /Journal ofPetroleum Science and Engineering 13 (1995) 219-232
-15 -5 5 15 25 J5
(b)
Rclativc Error %
a: Standing Correlation
Rclativc Error %
b: Laster Correlation
-__-
Cc) 10 -
.___._ _ 7
i 5-
/&.
_--
1 -1
o- -- _----_I
20
s 10
0
-10 0 10 20 30 40 50 0 20 40 60
Relative Error % Relative Error %
C: Vasquez and Beggs Correlation d: Glaso Correlation
I
-33 -10 10 xl 50
Rclativc Error %
.zDoklaand OsmanCorrdacion
IS
a I ”
/
/ \
1 1 I 1 I I
-Xl -10 10 30 50 70
Relative Error %
f AI-Marholm Comlation.
Fig. 4. Error distribution for bubblepoint pressure.
Table 3
A.M. Elsharkawy et al. /Journal of Petroleum Science und Engineering 13 (1995) 219-232 22s
Statistical accuracy of OFVF calculations for the Kuwaiti crude oils
Standing Labedi Vasquez-Beggs Glas0 Dokla-Osman A-Marhoun
Average error (%) 1.20 1.21 0.42 - I .31 0.60 - 0.26
Average absolute error (%) 3.17 3.11 3.41 3.19 3.38 2.12
Standard deviation 4.23 4.16 4.59 4.19 4.68 3.78
no H,S. Flash PVTdata were plotted versus differential
data for GOR as shown in Fig. 1 and for OFVF as shown in Fig. 2. These figures were used to adjust differential PVT data to represent flash for the few
mixtures that were not measured by flash separation.
The ranges of the data used in developing the seven
correlations examined in this study are compiled in Table 1. It is clear that these correlations have some
limitations, in that their data ranges do not cover the
properties of the Kuwaiti crudes. The Standing, Dokla
and Osman, Al-Marhoun, and Labedi correlations do
not cover the gas gravity range of the Kuwaiti crudes, while the Vasquez and Beggs, Al-Marhoun, and Dokla
and Osman correlations have limitations on the tem- perature range used in developing their correlations.
Finally, Dokla and Osman, and Labedi covered a nar- row range of tank-oil API in developing their correla-
tions.
3. Results and discussion
The prediction of the bubblepoint pressures were
made using the Standing, Lasater, Vasquez and Beggs, Glaso, Dokla and Osman, and Al-Marhoun correla- tions. The equations used in predicting bubblepoint
pressures are given in Appendix A. The separator pres-
sure and temperature were used to adjust the gas gravity
for the Vasquez and Beggs correlation. The API gravity and dead oil viscosity from differential tests were used to adjust the API gravity term as recommended by
Glaso. It was found that adjusting the API gravity for Glaso’s correlation did not improve its prediction capa- bility of the bubblepoint pressure. Therefore, it was
decided not to adjust the API gravity used in Glass’s
correlation in the present study. This is in agreement with the findings of Suttan and Farshad who computed a correction multiplier of 0.94 for the Gulf of Mexico crudes and reported that the use of this correction decreases the accuracy of Glaso’s correlation.
The estimated bubblepoint pressures were corrected for the presence of non-hydrocarbon gases for all cor- relations except those given by Dokla and Osman, and Al-Marhoun. The equations used in correcting the bub-
blepoint pressures are given in Appendix B. The deci-
sion not to correct the bubblepoint pressure estimated from the Al-Marhoun, and Dokla and Osman correla-
tions is based on the fact that the crude oils used in
those correlations contained non-hydrocarbon gases in concentrations similar to those measured for the
Kuwaiti crudes. Predictions of the bubblepoint oil FVF
were made using the Standing, Labedi, Vasquez and Beggs, Glass, Dokla and Osman, and Al-Marhoun cor-
relations. (The equations are reported in appendix C.)
4. Accuracy of the correlations
The accuracy of each correlation was determined by
studying the statistical errors (Walpole and Myers, 1985). The error analysis comprises the average per-
cent relative error, average absolute relative error and
standard deviation. The accuracies of the correlations were also checked by crossplots of experimental versus
estimated PVT parameters and plots of error distribu- tion histograms with overlaid normal distribution
curve.
It is important to note that the average percent rela- tive error can be misleading if the data points distribute
equally on both sides of the unite slope line. In such case, the average percent relative error can be very low but the calculated and measured values can be very different.
5. Accuracy of bubblepoint pressure correlations
Table 2 presents the errors and standard deviations for the six correlations used in this study. It is clear from this table, that Standing’s correlation shows the
226 A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 219-232
2.000
1.900
1.600
1.700
1.600
1.500
1.400
1.300
1.200
(Q 1.100
1.000
1.900
1.600
1.700
1600
1.500
1.400
1.300
,200
(d)
1.100
1000
1900
1.900
1.700
1.600
1.500
1.400
1.300
1.200
1.100
@I 1.000
2.000
1.900
1.600
1.700
1.600
1.500
1400
1.300
1.200
(e> '.'O"
1000
1900'
1 BOO
I 700
1600
1500
1.400
1300
1.200
1.100
Cc) 1.000
: 1.900
1.600
1.700
1.600
1.500
I.400
1.300
1.206
1.100
Cal l.ooa
Correlations a. 1 Standing b. Labcdi- C. Vasquez-Beggs l- d. Glas$
: Dokla-Osman Al-Marhoun
I
I.600 1.100 1.260 1.300 1.400 1.500 1.600 I.700 1.606 ,.900 r600
Experimental OFVF, m3/Std m3
Fig. 5. Crossplot for bubblepoint OFVF.
A.M. Elsharkawy ef al. /Journal ofPefroieum Science and Engineering 13 (1995) 219-232
40
30
i 2o B 6 10
0
20
0
20
s
P s 10
E
.! !I (4
Relative Error %
a: Standing Correlation b: Labedi Correlation
-5 0 5 10 15
Relative Error %
c: Vasquez and Beggs Correlation
-10 -5 0 5 10 15 -5 0 5 10 15 Relative Error % Relative Error %
e: DoWa and Oman Correlation
20
c 5 = 10 s
6
0
20
0
25
-a -3 2 7 12 1;
Relative Error %
Relative Error %
d: Glaso Correlation
L fi Al-Marhoun Cordation
Fig. 6. Error distribution for bubblepoint OFVF
228 A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 219-232
lowest errors and standard deviation followed by the
Lasater, and Dokla and Osman correlations, while the
Glaso, Vasquez and Beggs, and Al-Marhoun correla- tions show poor accuracy.
Crossplots of the bubblepoint pressures are pre-
sented in Fig. 3. These plots are grouped in one figure
with shifted vertical scales for the purpose of compar- ison. This figure demonstrates that the Standing and
Lasater correlations depicted closer scatter to the unite
slope line of perfect correlation than the others. The
Dokla and Osman, and Al-Marhoun correlations show wide scatter around the 45” line. The Glaso and Vas-
quez and Beggs correlations revealed their overesti-
mation. Error distribution plots are presented in Fig. 4. These
plots illustrated that Standing’s correlation has the
smallest relative error range, from - 15 to 35%, fol- lowed by Lasater’s correlation with relative error range
from - 20 to 50%, and having mean values about 7%
and 9%, respectively. In addition, the Vasquez and Beggs, and Glass correlations show wider error range
and peaks at 15% and 30%, respectively. This indicates a high overestimation and stronger positive skewed
error distribution than the others. In conclusions all six
correlations failed to predict acceptable bubble-point
pressures for the Kuwaiti crudes.
6. Accuracy of oil FVF correlations
Table 3 presents the errors and standard deviation
for the calculated OFVF. Al-Marhoun’s correlation
shows the smallest average relative error, average abso-
lute error, and standard deviation followed closely by
the others.
Crossplots of bubblepoint OFVF (Fig. 5) illustrate that all the correlations have a scatter around the perfect correlation line. However, Al-Marhoun’s correlation shows closer scatter to the perfect correlation line than
the others. Error distribution plots presented in Fig. 6 reveals
that Al-Marhoun’s correlation has the smallest error
range and the normal curve peak is close to zero. The other correlations show comparable error ranges and skewness.
Comparing Figs. 4 and 6, it is obvious that the bub- blepoint OFVF correlations showed better accuracy than the bubblepoint pressure correlations, because by
nature of their values, bubble-point OFVFs have a nar-
row range of values compared to their absolute values. This is very different from the values of bubble-point
pressures which have a wide range compared to their possible absolute values. From this observation it can
be seen that it is highly possible that the bubble-point OFVF correlations would give the estimates that are
much closer to the measured values than those given
by the bubble-point pressure correlations and all rela- tive errors calculated for the bubble-point OFVF esti-
mation can be much lower than those for the bubble-point pressure estimation.
7. Conclusions
The objectives of the present study are to character- ize the Kuwaiti crude oils and study the recently devel-
oped correlations in the area and those most often used.
It also aims at assessing the accuracy of these correla- tions for their applicability in predicting the PVTprop- erties of the Kuwaiti crudes.
Although Standing’s correlation was developed
from Californian crudes and Lasater’s correlation from
North and South American crudes, and both contained essentially no non-hydrocarbon gases, they yield the
least errors for the bubblepoint pressures, but such
errors are unacceptable. All the OFVF correlations studied showed a very
close range of accuracy. The Al-Marhoun, and Dokla and Osman correlations (although developed for Mid-
dle East and UAE crudes, respectively, with identical
ranges of non-hydrocarbon gases and API gravity, and
sometimes produced from the same formation) did not
satisfactorily estimate the bubblepoint pressure for the
Kuwaiti crudes. Because all published correlations con- sidered in this study failed to give satisfactory predic- tions, it is recommended that a correlation for bubble point pressure and bubble point OFVF be developed
for the Kuwaiti crudes.
8. Nomenclature
B ob
B,’ YAP1
Oil FVF at bubble point pressure, RB / STB [ res m3/stock-tank m3] Correlating number for calculating Bob Tank oil gravity (“API)
A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 2 I9-232 229
YiPI
* YAPIcon
YAPIcon
Residual oil API from differential separation
Corrected residual oil API from differential separation
Corrected tank oil API from flash separation
Total gas specific gravity (air = 1 .O)
Total gas specific gravity from separator condition of 100 psi Tank oil specific gravity (water = 1 .O)
Effective tank oil molecular weight Reservoir pressure, Psia [ kPa] Bubble point pressure, Psia [ kPa]
Correlating number for bubble point
Bubble point pressure factor
Separator pressure, Psia [ kPa]
Solution GOR, SCF/STB [ Std m3/ stock-tank m”]
Reservoir temperature, “F [“Cl
Reservoir temperature “R [“K] Dead oil viscosity at reservoir temperature, cP [ mPa.s] Mole fraction of gas
9. SI metric conversion factors
“API= 141.5/( 131.5+ y,,) = gm/cm3 bbl x 1.589 873 E - 01 =m3
DegreeF (“F-32)/1.8 =“C Degree R “F + 460 =“R
psia X 6.894 757 EOO = kPa SCF/STB Y 1.801 175 E - 01 = Stdm3/m3
Acknowledgements
The authors would like to thank the Ministry of Oil and the Kuwait Oil Company (KOC) for providing the information used in the present study.
Appendix A
Bubblepoint pressure correlations
Standing
P, = 18.2 [ (R”)o.“3antilog
(0.00091?-O.O125y,,,) - 1.41
Lasater
p b
= W(T+459.67)
Yg
M,=725.32143- 16.03333YApI+0.09524$.p1
p,=O.38418- 1.20081Y,+9.64868Y;
Vasquez and Beggs
Cl& P,= (- antilog - c3YAPI ) I/c2
Ygs T+ 459.67
YAPI 2 3o
C, = 27.64 c, = 1.0937
C,= 11.172
YAP1 > 30
C, = 56.06 C,= 1.1870
c3 = 10.393
G Las@
Pb = antilog [ 1.7669 + 1.7447 log p;
-0.30218(logp,‘)*]
where:
pb’ = ($8190.172
YS ‘YAP1 - 0.989
L YAPIcom = antilog[ up&]
a=3.184(10-“)T3.44
b= [ 10.213(logT) -36.4471-l
Y~PIcolT YAPIcorr
=-
YiPI YAP1
230 A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 219-232
Al-Marhoun
P, = 5.38088
X 10-3~0.715082 - 1.877840 5 7,
7.1437 Y”
1.32657 T,
Dokla and Osman
P, = 0.836386
X ~~4y,l.0104Y~107YY'~,0.Y52S84~7Z4047
Appendix B
Effect of Non-hydrocarbon gases
Glas#
Nitrogen:
C,,= l.O+ [( -2.65x 10-4y,,I+5.5x 10-3)T
+(0.0931yA,,+0.8295)]Y,,,2+[(1.954
X lo-“$$p)T+ (O.O27y,,,-2.366)] (YN2)2
where Y,, is the mole fraction of nitrogen. Carbon dioxide:
C co2 = 1.0 - 693.8Yco2T - ‘.s33
where Y,,, is the mole fraction of C02. Hydrogen sulfide:
c H2S= l.O- (0.9035 +0.0015y,&Y,,,
+".019(45-~,4PI)(yH2S)2
C= 15.85 +2.86N,,-0.,07T
Appendix C
OFVF correlations
Standing
Vasquez and Beggs
B,,b=1.0+C,R,+C2(T-60)(T)
+C R (T-60)(+ 3 s
%
API I 30 API> 30 C1 =4.677x 1O-4 C, =4.670x 1O-4 c, = 1.751 x 1o-s c,= 1.100x 1o-s c,= -1.8106X 1o-8 c3 = 1.337 x lo9
Glas@
B,, = 1 .O + antilog
[ -6.58511+2.9132910gB~b-0.27683(logB,’,)2]
where:
B,‘b = R,( yg/y,)o.526 + 0.968T
Al-Marhoun
B,, = 0.497069 + 0.862963 X lo- 3T, + 0.182594
X 10-2F+0.318099x 10-5F2
where:
F= ~0.742390 .323294 -1.202040 s g Yo
Dokla and Osman
B,,=0.431935 X 10-l $0.156667
x 10p2T,+0.139775
X 10-2F+0.380525
x lo-‘F2
where:
Table 4
A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering I3 (1995) 219-232 231
Fluid property of the Kuwaiti crudes
No. Bubble point pressure Bubble point oil FVF Solution GOR Tank oil gravity Reservoir temp. Non-hydrocarbon gases
(Kpa) (m3/Std m3) (Std m3/Stock m’) (“C)
Flash Diff. Flash Diff. Nz (%) CO> (%) H,O(%)
1 17535
2 16645
3 15590
4 12706
5 13323
6 15241
7 10994
8 12535
9 2171
10 5069
11 4637
12 25618
13 18186
14 15652
15 17193
16 12878
17 16481
18 18111
19 10062
20 15138
21 15823
22 10912
23 11419
24 11521
25 11110
26 13131
27 13309
28 13199
29 18734
30 16439
31 19727
32 29331
33 17981
34 15617
35 11179
36 12672
37 19536
38 22741
39 19042
40 9007
41 17741
42 29968
43 13665
44 19625
I .704
1.664
1.634
1.383
1.385
1.510
1.292
I .368
1.057
1.138
1.127
1.533
I.416
1.338
1.355
1.243
1.350
1.273
1.020
1.243
1.342
I.238
1.270
1.269
1.226
I.227
1.330
1.199
1.325
1.969
1.936
1.859
1.519
1.522
I.681
1.399
1.500
1.076
1.178
1.149
1.671
1.454
1.369
1.438
1.279
I.437
1.493
1.197
1.280
1.407
1.235
I.311
1.289
1.267
1.323
1.332
1.289
I.411
I .470
1.590
1.710
1.470
1.320
I.240
1.300
1.530
1.610
1.450
1.250
1.450
1.770
1.260
1.520
183.6
169.9
157.4
89.6
88.0
126.3
80.9
104.7
6.1
31.0
24.6
180.4
111.8
98.0
112.2
70.9
99.0
135.0
42.6
75.9
98.8
69.5
82.8
88.2
54.0
82.8
90.7
67.0
128.2
246.5 0.814 115.6
232.4 0.812 121.1
209. I 0.818 121.1
127.5 0.828 120.6
118.1 0.823 116.7
192.5 0.838 95.6
104.7 0.836 104.4
130.9 0.822 116.7
6.9 0.920 71.1
40.2 0.910 81.1
29.4 0.917 81.1
213.4 0.852 85.6
133.7 0.861 87.2
115.2 0.872 76.7
129.5 0.874 81.7
79.1 0.906 80.0
127.9 0.73 82.2
138.6 0.869 80.0
54.7 0.930 73.9
89.4 0.904 80.0
117.4 0.883 81.1
86.4 0.872 54.4
98.3 0.856 56. I
94.4 0.859 56.7
72.7 0.872 55.6
103.7 0.859 55.6
107.7 0.862 57.2
108.1 0.873 57.2
129.8 0.887 73.9
132.7 0.880 78.9
175.6 0.890 95.6
249.3 0.860 94.4
131.8 0.870 88.9
95.8 0.890 78.9
57.9 0.920 78.9
83.9 0.906 76.7
157.6 0.860 82.2
185.0 0.860 89.4
125.4 0.890 98.9
63.8 0.900 77.8
134.5 0.860 77.8
236.9 0.860 93.9
79.1 0.910 77.8
151.0 0.860 88.9
0.20 3.63 0.16
0.16 3.92 1.66
0.29 3.67 2.44
0.21 2.09 0.20
0.18 2.12 0.11
0.00 3.91 1.37
0.13 2.35 0.06
0.78 2.09 0.84
4.40 4.4 1 0.00
0.49 6.90 1.21
0.67 6.80 0.82
0.03 0.63 0.00
0.39 0.68 0.00
0.32 0.39 0.00
0.30 0.30 0.00
0.35 0.43 0.00
0.40 0.45 0.00
0.48 0.42 0.00
0.83 0.43 0.00
0.52 0.15 ~3.00
0.29 0.4 1 0.00
1.310 0.68 0.00
I .030 0.15 IO.00
1.300 0.33 Il.00
0.710 2.83 0.00
0.00 2.81 0.00
1.650 0.92 0.00
0.760 0.28 0.00
1.70 2.70 0.00
232 A.M. Elsharkawy et al. /Journal of Petroleum Science and Engineering 13 (1995) 219-232
404020 - 0.882605 F+.773572$. ‘yo
Labedi
Appendix D
Fluid property of the Kuwaiti crudes
The fluid properties of the Kuwaiti crudes are listed
in Table 4.
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Recommended