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Evaluation of proposed correlation equations for oil formation volume
factors at reservoir pressures less than bubblepoint pressure
The data set described in table 3-9 was used to evaluate published
correlation equations of oil formation volume factors at bubblepoint
pressures and below. Each of the 718 reservoir fluid studies had a
separator test and several lines of differential liberation data for pressures
below bubblepoint pressure. Values of oil formation volume factors for
use in evaluating published correlation equations were calculated with
a combination of these differential liberation and separator test data
using the procedure of Amyx et al.
39
None of these data were used in preparing any of the published oil
formation volume factor correlation equations.
Table 3-20 shows that this equation may be used with good results
for reservoir pressures below the bubblepoint pressure.
Table 3-20. Evaluation of published oil formation volume factor correlation equations for reservoir
pressures equal to and less than bubblepoint pressures reveals the most reliable correlations.
Predicted oil formation volume factors
ARE, %
Correlation
AARE, %
Equation (3.21b),
ρ
oR
from equations (3.19a)-(3.19g),
R
s
from equations (3.8a)-(3.8f),
p
b
from data
0.27
1.53
Equation (3.21b),
ρ
oR
from equations (3.19a)-(3.19g),
R
s
from equations (3.8a)-(3.8f),
p
b
from equation (3.7)
0.16
2.25
Casey-Cronquist (1992)*,
p
b
from data 1.31 3.09
Kartoatmodjo-Schmidt (1994) -0.79 3.32
Standing (1977)* -1.89 3.50
Casey-Cronquist (1992)*,
p
b
from equation (3.7) 1.38 3.52
Levitan-Murtha (1999)
a
-0.97 3.72
Vazquez-Beggs (1980) -2.19 4.23
Ahmed (1989),
p
b
from equation (3.7) 1.22 4.43
Glaso (1980)
†
-4.06 5.12
Hanafy et al. (SPE 37439, 1997)* 4.48 7.23
Carlson (1997),
p
b
from equation (3.7) -8.51 9.37
a
Levitan, L.L. and Murtha, M. “New Correlations Estimate P
b
, FVF.”
Oil & Gas Journal
. Vol. 97 (March 8, 1999) 70-76.
* Author restricted correlation to a specific geographical area.
†
Author indicated correlation was for use at bubblepoint pressure only.
The data described in table 3-9 were sorted and sliced into 10 subsets
with more than 500 data points in each subset. Values of ARE and AARE
were calculated for subsets sorted by reservoir temperatures, stock-tank
oil gravities, reservoir pressures, and measured oil formation volume
factors. The results may be seen in figures 3-25 through 3-28.
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