oil correlations
TRANSCRIPT
Home > Reference Materials > Calculations & Correlations > Oil Correlations
Oil Correlations Subtopics:
Vasquez and Beggs (Generally Applicable) Al-Marhoun 1985 (Saudi Arabian Oil) Beggs and Robinson De Ghetto et al. (Heavy and Extra-Heavy Oils) Glaso (North Sea Oil) Hanafy et al. (Egyptian Oil) Khan et al. (Saudi Arabian Oil) Ng and Egbogah Petrosky and Farshad (Gulf of Mexico) Standing (California Oil) Velarde et al. (Reduced Variable Approach) Oil Correlation Limits
Vasquez and Beggs (Generally Applicable)
Vasquez and Beggs is a generally applicable correlation containing equations for solution gas oil
ratio, oil formation volume factor, and oil compressibility. The correlation was developed from data
obtained from over 600 laboratory PVT analyses gathered from fields all over the world. The data
used in the development of the correlation covers a wide range of pressures, temperatures, and oil
properties. The correlation divides the data into two groups: one for oil gravity over 30°API and one
at and below 30°API.
Bubble Point Pressure
Solution Gas Oil Ratio
Oil FVF – Saturated
Oil FVF – Undersaturated
Compressibility – Saturated
Compressibility – Undersaturated
Coefficient γo ≤ 30o API γo > 30o API
A1 0.0362 0.0178
A2 1.0937 1.1870
A3 25.7240 23.9310
C1 0.0362 0.0178
C2 1.0937 1.1870
C3 25.7240 23.9310
Al-Marhoun 1985 (Saudi Arabian Oil)
The Al-Marhoun correlation contains equations for estimating bubble point pressure, solution gas oil
ratio, and oil formation volume factor for Saudi Arabian oils. 75 bottomhole fluid samples from 62
reservoirs in Saudi Arabia were used in the development of these correlations. The author claims
that the correlations should be valid for all types of gas-oil mixtures that share similar properties as
those used in the derivation. According to the author, the average errors and standard deviations
were lower with the Al-Marhoun correlation than with the Standing and Glaso correlations for Saudi
Arabian crude oils. Note that temperature is measured in Rankine.
Bubble Point Pressure
Solution Gas Oil Ratio
where:
a = - 2.278475 * 10-9
b = 7.02362 * 10-3
c = - 64.13891 – p
Oil FVF – Saturated
Oil FVF – Undersaturated
The oil compressibility used in this equation is obtained from the Vasquez and Beggs correlation.
Beggs and Robinson
Beggs and Robinson developed an empirical correlation for determining the viscosity of dead oil.
The correlation originated from analyzing 460 dead oil viscosity measurements. The data set from
which the results were obtained ranged from 16°API to 58°API and 70°F to 295°F. The correlation
tends to overstate the viscosity of the crude oil when dealing in temperature ranges below 100°F to
150°F.
Viscosity
where:
De Ghetto et al. (Heavy and Extra-Heavy Oils)
The De Ghetto et al. correlation contains modified PVT correlations for estimating bubble point
pressure, solution gas oil ratio, oil formation volume factor (FVF), oil compressibility, and oil viscosity
for heavy (10° < API < 22.3°) and extra-heavy oils (API < 10°). The oils used for developing the
correlation came from reservoir fluid samples taken from the Mediterranean Basin, Africa, and the
Persian Gulf. When comparing published correlations, De Ghetto et al. decided that the Vasquez
and Beggs correlation estimated the oil formation volume factor with minimal error, and therefore no
further modification was needed. Note that in contrast with other correlations, the De Ghetto et al.
correlation requires the pressure and temperature at the separator.
Heavy Oils (10° < API < 22.3°)
Bubble Point Pressure
Solution Gas Oil Ratio
Oil FVF – Saturated
where:
A1, A2, and A3 are Vasquez and Beggs constants for API ≤ 30o:
A1 = 4.677*10-4
A2 = 1.751*10-5
A3 = -1.811*10-8
Oil FVF – Undersaturated
Compressibility – Saturated
Compressibility – Undersaturated
Viscosity – Dead Oil
Viscosity – Saturated
Viscosity – Undersaturated
Extra Heavy Oils (API < 10°)
Bubble Point Pressure
Solution Gas Oil Ratio
Oil FVF – Saturated
where:
A1, A2, and A3 are Vasquez and Beggs constants for API ≤ 30o:
A1 = 4.677*10-4
A2 = 1.751*10-5
A3 = -1.811*10-8
Oil FVF – Undersaturated
Compressibility - Saturated
Compressibility – Undersaturated
Viscosity – Dead Oil
Viscosity – Saturated
Viscosity – Undersaturated
Glaso (North Sea Oil)
The Glaso correlation contains equations for estimating bubble point pressure, solution gas oil ratio,
and oil formation volume factor for North Sea oils. The author claims that the correlation should be
valid for all types of oil and gas mixtures after correcting for non-hydrocarbons in the surface gases
and the paraffinicity of the oil. According to the author, the correlation more accurately predicts the
oil properties of North Sea oils than the Standing correlation.
Bubble Point Pressure
Solution Gas Oil Ratio
where:
x = 10log(x)
a = -0.30218
b = 1.7447
c = 1.7669 – log(p)
Oil FVF – Saturated
Oil FVF – Undersaturated
Note: The oil compressibility used in this equation is obtained from the Vasquez and
Beggs correlation.
Hanafy et al. (Egyptian Oil)
The Hanafy et al. correlation contains equations for estimating bubble point pressure, solution gas
oil ratio, oil formation volume factor, oil compressibility, oil viscosity, and oil density for Egyptian oils.
The compressibility correlation assumes constant compressibility after the bubble point. This
correlation is independent of oil gravity and reservoir temperature. The PVT data used in the
derivation of the correlations was gathered from the Gulf of Suez, Western Desert, and Sinai
regions. The authors claim that the correlations can be used to estimate oil properties for a wide
range of crude oils ranging from heavy to volatile oils. However our observations are that it appears
to be closer to the properties of light oils.
Bubble Point Pressure
Solution Gas Oil Ratio
Rs = 0 when p ≤ 157.28
Oil FVF – Saturated
Oil FVF – Undersaturated
Density – Saturated
Density – Undersaturated
Compressibility – Saturated
Note: This equation uses the Vasquez and Beggs correlation.
Compressibility – Undersaturated
Oil Viscosity
Khan et al. (Saudi Arabian Oil)
The Khan et al. correlation contains equations for estimating oil viscosity at, above, and below the
bubble point for Saudi Arabian oils. The study used data from 75 bottomhole samples, which were
taken from 65 Saudi Arabian reservoirs. The authors claim that this correlation gives the most
accurate predictions for Saudi Arabian crude oils, as compared to the Beggs and Robinson, Beal,
and Chew and Connally correlations. For this correlation, oil gravity must be less than 1 (10° API).
Oil Viscosity (API < 10°)
p = pb
where:
p > pb
p < pb
Ng and Egbogah
The Ng and Egbogah correlation contains two methods for calculating dead oil viscosity using a
modified Beggs and Robinson viscosity correlation and a correlation that uses the pour point
temperature. Pour point temperature is the lowest temperature at which the oil is observed to flow
when cooled and examined under conditions prescribed in ASTM D97. The purpose of introducing
the pour point temperature into the correlation is to reflect the chemical composition of crude oil into
the viscosity correlation. To obtain the viscosity for live oils, the dead oil correlations are used with
the Beggs and Robinson viscosity correlation. The data used to derive the correlations was taken
from the Reservoir Fluids Analysis Laboratory of AGAT Engineering Ltd., using a total of 394 oil
systems.
Dead Oil
-50°C < Tpp < 15°C
Live Oil – Saturated
where μod is defined using the modified Beggs and Robinson correlation.
Live Oil - Undersaturated
Petrosky and Farshad (Gulf of Mexico)
The Petrosky and Farshad correlation contains equations for estimating bubble point pressure,
solution gas oil ratio, oil formation volume factor, and oil compressibility for Gulf of Mexico oils. The
correlation was developed using fluid samples taken from offshore regions in Texas and Louisiana
(Galveston Island eastward through Main Pass). The authors claim that these correlations provide
improved results over other correlations for the Gulf of Mexico, including those published by
Standing, Vasquez and Beggs, Glaso, and Al-Marhoun.
Bubble Point Pressure
where:
Solution Gas Oil Ratio
where:
Oil FVF – Saturated
Oil FVF – Undersaturated
Compressibility – Saturated
where dRs / dp is from Vasquez and Beggs.
Compressibility – Undersaturated
where 2.464 * 10-5 < co < 3.507 * 10-5
Standing (California Oil)
The Standing correlation contains equations for estimating bubble point pressure, solution gas oil
ratio, and oil formation volume factor for California oils. 105 experimentally determined data points
on 22 different oil-gas mixtures from California were used in the development of the correlations.
Bubble Point Pressure
Solution Gas Oil Ratio
Oil FVF – Saturated
Oil FVF – Undersaturated
The oil compressibility used in this equation is obtained from the Vasquez and Beggs correlation.
Velarde et al. (Reduced Variable Approach)
The Velarde et al. correlation contains equations for estimating bubble point pressure, solution gas
oil ratio, and oil formation volume factor. The bubble point pressure correlation was based on 728
data sets. The solution gas oil ratio was based on 2097 data sets.
Bubble Point Pressure
Solution Gas Oil Ratio (p = pb)
Solution Gas Oil Ratio (p < pb)
Note: All pressures in the above equations are measured in psig.
Reduced Variable Approach
The reduced solution gas oil ratio is defined as the solution gas oil ratio divided by the solution gas
oil ratio at the bubble point. The reduced pressure is defined as the pressure divided by the bubble
point pressure. Using the above relationship the reduced solution gas oil ratio and the solution gas
oil ratio at the bubble point are used to solve for the actual solution gas oil ratio at any pressure
below the bubble point.
A Coefficients B Coefficients C Coefficients
A0 = 9.73 x 10-7 B0 = 0.022339 C0 = 0.725167
A1 = 1.672608 B1 = 1.004750 C1 = 1.485480
A2 = 0.929870 B2 = 0.337711 C2 = 0.164741
A3 = 0.247235 B3 = 0.132795 C3 = 0.091330
A4 = 1.056052 B4 = 0.302065 C4 = 0.047094
Oil FVF – Saturated
In the above equation an initial estimate of ρpo is calculated as follows:
Once this initial value is known, ρpo is calculated through a 10 step iteration process using the
following equations. The values from the ninth and tenth iterations are averaged to yield a final value
for ρpo.
Oil FVF – Undersaturated
The oil compressibility used in this equation is obtained from the Vasquez and Beggs correlation.
Note: All pressures in the above equations are measured in psia.
Correlation Limits
Variable Rs Correlation Limits pbp Correlation Limits
T 70 - 307 oF 74 - 327 oF
pb 106 - 5312 psia 70 - 6700 psia
Bob 1.040 - 2.082 bbl/stb N/A
Rs or Rsb 102 - 1808 scf/stb 10 - 1870 scf/stb
γg 0.561 - 1.101 0.556 - 1.367
γo 11.6 - 53.4 oAPI 12 - 55 oAPI
Oil Correlation Limits
Correlation T (oF) p (psia) pb (psia) Bo
(Rbbl/stbbl) Rs
(scf/stbbl)
Al-Marhoun 1985 (Saudi Arabian Oil)
75 - 240 107 - 4315 1.02 - 2.42 24 - 1901
De Ghetto et al. (Heavy and Extra-Heavy Oils)
131.4 - 250.7
1038.49 - 7411.54
208.86 - 4021.96
1.057 - 1.362 17.21 - 640.25
Glaso (North Sea Oil) 80 - 280 400 - 4000 150 - 7127 1.087 - 2.588 90 - 2637
Hanafy et al. (Egyptian 1038.49 - 36 - 5003 1.032 - 1.35 7 - 4272
Oil) 7411.54
Khan et al. (Saudi Arabian Oil)
75 - 240 14.7 - 5015 107 - 4315 24 - 1901
Ng and Egbogah 70 - 295
Petrosky and Farshad (Gulf of Mexico Oil)
114 - 288 1700 - 10692
1574 - 6523
1.1178 - 1.6229
217 - 1406
Standing (California Oil) 60 - 260 (pbp)
100 - 260 (Bo)
200 - 6000 1.024 - 2.15 20 - 1425
Vasquez and Beggs (Generally Applicable)
140.7 - 9514.7
Velarde et al. (Reduced Variable Approach)
See Velarde et al
See Velarde et al
See Velarde et al
See Velarde et al
Correlation gg γo μo (cp) μos (cp) μod (cp)
Al-Marhoun 1985 (Saudi Arabian Oil)
0.752 - 1.367 14.3 - 44.6
De Ghetto et al. (Heavy and Extra-Heavy Oils)
0.623 - 1.517 6 - 22.3 2.4 - 354.6
2.1 - 295.9
7.7 - 1386.9
Glaso (North Sea Oil) 0.65 - 1.276 22.3 - 48.1 0.119 - 106.6
Hanafy et al. (Egyptian Oil) 0.752 - 1.367 14.3 - 44.6 0.13 - 71
Khan et al. (Saudi Arabian Oil) 0.13 - 77.4
Ng and Egbogah 5 - 58
Petrosky and Farshad (Gulf of Mexico Oil)
0.5781 - 0.8519
16.3 - 45
Standing (California Oil) 0.5 - 1.5 16.5 - 63.8
Vasquez and Beggs (Generally Applicable)
0.511 - 1.351 15.3 - 59.5
Velarde et al. (Reduced Variable Approach)
See Velarde et al
See Velarde et al
Correlation Tsp (oF) psp (psia)
De Ghetto et al. (Heavy and Extra-Heavy Oils) 59 - 177.8 14.5 - 752.2
Correlation ρo (g/cm3) ρob (g/cm3)
Hanafy et al. (Egyptian Oils) 0.648 - 1.071 0.428 - 0.939
Copyright © 2012 Fekete Associates Inc.