I
DEVELOPMENT OF AN EXPERT SYSTEM FOR
RESERVOIR FLUID PVT PROPERTIES
CORRELEATIONS
Presented By
Ahmed Moustafa Abd El-Rahman Al-Zahaby
B.Sc. in Petroleum Eng. Al-Azhar University (2007)
A Thesis Submitted to the Department of Mining, Petroleum, and
Metallurgical Engineering
Faculty of Engineering, Cairo University
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
FACULTY OF ENGINEERING, CAIRO UNIVERSITY
GIZA, EGYPT
2012
II
DEVELOPMENT OF AN EXPERT SYSTEM FOR
RESERVOIR FLUID PVT PROPERTIES
CORRELEATIONS
Presented By
Ahmed Moustafa Abd El-Rahman Al-Zahaby
B.Sc. in Petroleum Eng. Al-Azhar University (2007)
A Thesis Submitted to the Department of Mining, petroleum, and
Metallurgical Engineering
Faculty of Engineering, Cairo University
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
Under the Supervision of
Prof. Dr. Mohamed Helmy Sayyouh
Professor of Petroleum Engineering
Cairo University
Prof. Ahmed El-Banbi
Professor of Petroleum Engineering
Cairo University
FACULTY OF ENGINEERING, CAIRO UNIVERSITY
GIZA, EGYPT
2012
III
DEVELOPMENT OF AN EXPERT SYSTEM FOR
RESERVOIR FLUID PVT PROPERTIES
CORRELEATIONS Presented By
Ahmed Moustafa Abd-El Rahman Al-Zahaby
B.Sc. in Petroleum Eng. Al-Azhar University (2007)
A Thesis Submitted to the Department of Mining, Petroleum, and
Metallurgical Engineering
Faculty of Engineering, Cairo University
In Partial Fulfillment of the Requirements for the Degree of
MASTER OF SCIENCE
IN
PETROLEUM ENGINEERING
Approved by the
Examining Committee
…………………………………………
Prof. Dr. Mohamed Helmy Sayyouh
Faculty of Engineering, Cairo University, Thesis Main Advisor
…………………………………………
Prof. Dr. Ahmed El-Banbi
Faculty of Engineering, Cairo University, Thesis Main Advisor
…………………………………………
Prof. Dr. M. Khairy
Faculty of Engineering, Cairo University, Member
…………………………………………
Prof. Dr. Ismail Mahgoub
Faculty of Engineering, Cairo University, Member
FACULTY OF ENGINEERING, CAIRO UNIVERSITY
GIZA, EGYPT
2012
IV
ABSTRACT
DEVELOPMENT OF AN EXPERT SYSTEM FOR
RESERVOIR FLUID PVT PROPERTIES
CORRELEATIONS
Accurate determination of the crude oil PVT properties is essential for solving many
reservoir engineering, production engineering, and surface production and operational
problems. A large number of PVT correlations for oil exist in the petroleum literature and
numerous studies are also present for with data favoring one correlation over the other. In
the absence of PVT data from laboratory experiments, it is often difficult to choose which
correlation to use to calculate different PVT properties. We approached this problem in
two ways. First, we developed an expert system that checks the input parameters (e.g.
reservoir parameters) against the valid ranges of input data for different correlations, and
then recommends which correlations to use for specific input parameters. Second, we
tested all available PVT correlations for black oil on a database of selected 35 Egyptian
crudes to develop guidelines on which correlations to use for each PVT property for the
specific range of input data. These specific crudes were selected to allow testing of those
guidelines on a wide range of reservoir input data for black oils. Our database included
oils with oAPI ranging from 17 to 51, gas-oil-ratios of 8 to 7,800 scf/STB, formation
volume factor at bubble point of 1.04 to 4.47 bbl/STB, bubble point pressures of 60 to
4739psia, and reservoir temperatures of 40 to 270 ◦F.
The present work included 14 bubble points, 6 solution-gas-oil ratio, 15 formation
volume factors, 13 oil compressibilities, 14 dead oil viscosities, 9 saturated oil viscosities,
10 under saturated oil viscosities ,12 under-saturated densities, 2 total formation volume
factors and 2 saturated density correlations. In addition to 6 dew point pressure
correlations and 8 gas compressibility factors.
V
Based on this study, guidelines for selecting an appropriate correlation for PVT
properties are introduced .These guidelines are recommended in programming of PVT
correlations regardless of their geographic origin.
VI
Dedication
To my dear mother, I am not able to thank you, because
whatever I did, you deserve more.
VII
ACKNOWLEDGEMENT
All praise to Allah, the Almighty, who gave me the confidence to carry out this work.
I wish to express my great gratitude to professor Dr. Mohamed Helmy Sayyouh and Prof.
Ahmed Hamdi El-Banbi, Mining Petroleum, and Metallurgical Department, Faculty of
Engineering, Cairo University for selecting the study subject, supervising the work, and
for valuable guidance during the preparation and for their continuous suggestions and
encouragement.
I am grateful to Dr Ismail Mahgoub who allowed me to use some industry resources and
useful materials.
Also my acknowledgments to all my friends and staff members who made my stay here
at Cairo and the British University in Egypt. Last but not the least; I am grateful to my
mother and my father for their understanding and affection throughout my life.
Acknowledgements are also extended to my professor Dr. Selim Zeidan of Faculty of
Engineering Al-Azhar University for his continuous support and careful review of the
manuscript.
VIII
CONTENTS Page
ABSTRACT ......................................................................................................................................................... IV
DEDICATION ..................................................................................................................................................... VI
ACKNOWLEDGEMENT .......................................................................................................................................... VII
CONTENTS .......................................................................................................................................................... VIII
LIST OF TABLES ..................................................................................................................................................... XI
LIST OF FIGURES .................................................................................................................................................. XIII
NOMENCLATURE .............................................................................................................................................. XIV
1.CHAPTER 1 .......................................................................................................................................................... 1
INTRODUCTION ..................................................................................................................................................... 1
2.CHAPTER 2 .......................................................................................................................................................... 4
LITERATURE REVIEW .............................................................................................................................................. 4
2.1 OIL CORRELATIONS ............................................................................................................................................. 5 2.1.1 BUBBLE POINT PRESSURE ....................................................................................................................................... 5
2.1.2. Solution Gas –Oil Ratio .................................................................................................................................... 10 2.1.3. Under-saturated Isothermal Oil Compressibility ............................................................................................. 11 2.1.4. Under-saturated Oil Formation Volume Factor .............................................................................................. 14 2.1.5. Bubble point Oil Formation Volume Factor..................................................................................................... 15 2.1.6. Oil Viscosity: .................................................................................................................................................... 19 2.1.6.1. Under-saturated Oil Viscosity .................................................................................................................... 19 2.1.6.2. Bubble Point (Saturated) Oil Viscosity ....................................................................................................... 21 2.1.6.3. Dead Oil Viscosity....................................................................................................................................... 23 2.1.7. Under-Saturated Oil Density ........................................................................................................................... 25 2.1.8. Saturated Oil Density ...................................................................................................................................... 26 2.2. Gas correlations .............................................................................................................................................. 27 2.2.1. Compressibility Factor of Gas .......................................................................................................................... 27 2.2.1.1. Direct calculations ...................................................................................................................................... 27 2.2.1.2. Indirect calculations ................................................................................................................................... 29 2.2.2. Dew point pressure ......................................................................................................................................... 30 2.2.3. Gas Viscosity µg ............................................................................................................................................... 34 2.2.4. Hydrate Temperature...................................................................................................................................... 35 2.2.5. Critical properties (Tc & Pc) ............................................................................................................................. 36 2.3. Water correlations .......................................................................................................................................... 38 2.3.1. Solution Gas Water Ratio (Rsw): ..................................................................................................................... 38 2.3.2. Formation Water Volume Factor (Bw): ............................................................................................................ 39 2.3.3. Density of Formation Water (ρw): ................................................................................................................... 39 2.3.4. The Coefficient of Isothermal Compressibility of Brine (cw): .......................................................................... 40 2.3.5. Formation Water Viscosity (µw): .................................................................................................................... 41 2.3.6. Formation Water Content of Gas Wfw ............................................................................................................. 43
3.CHAPTER 3 ........................................................................................................................................................ 44
IX
OBJECTIVES AND STATEMENT OF THE PROBLEM ................................................................................................. 44
3.1 THE PROBLEM .................................................................................................................................................... 44 3.2 OBJECTIVES OF THE STUDY .................................................................................................................................... 44
4.CHAPTER 4 ........................................................................................................................................................ 46
RESERVOIR FLUID CORRELATIONS ....................................................................................................................... 46
4.1 OIL CORRELATIONS ............................................................................................................................................. 46 4.1.1. INTRODUCTION ............................................................................................................................................. 46 4.1.2. PROGRAMMING OF PVT OIL PROPERTIES CORRELATIONS...................................................................................... 46 4.1.3. EVALUATION OF PVT OIL CORRELATIONS ............................................................................................................ 47 4.1.3.1. BUBBLE POINT PRESSURE ........................................................................................................................... 47 4.1.3.2. SOLUTION GAS –OIL RATIO ........................................................................................................................ 47 4.1.3.3. UNDER-SATURATED ISOTHERMAL OIL COMPRESSIBILITY ................................................................................... 47 4.1.3.4. UNDER-SATURATED OIL FORMATION VOLUME FACTOR .................................................................................... 48 4.1.3.5. BUBBLE POINT OIL FORMATION VOLUME FACTOR ........................................................................................... 48 4.1.3.6. OIL VISCOSITY .......................................................................................................................................... 48 4.1.3.6.1. UNDER-SATURATED OIL VISCOSITY .......................................................................................................... 48 4.1.3.6.2. BUBBLE POINT (SATURATED) OIL VISCOSITY .............................................................................................. 48 4.1.3.6.3. DEAD OIL VISCOSITY ............................................................................................................................. 49 4.1.3.7. UNDER-SATURATED OIL DENSITY ................................................................................................................. 49 4.1.3.8. TOTAL FORMATION VOLUME FACTOR ............................................................................................................ 49 4.2 GAS CORRELATIONS ............................................................................................................................................ 69 4.2.1. DATA DESCRIPTION ........................................................................................................................................ 70 4.3 WATER CORRELATIONS ........................................................................................................................................ 82
5.CHAPTER 5 ........................................................................................................................................................ 89
DEVELOPMENT OF AN EXPERT SYSTEM ............................................................................................................... 89
5.1INTRODUCTION............................................................................................................................................... 89
5.2PVT EXPERT SYSTEM DEVELOPMENT .............................................................................................................. 90
5.2.1.KNOWLEDGE ACQUISITION ......................................................................................................................... 90
5.2.2.SYSTEM FORMULATION .............................................................................................................................. 90
5.3PVT EXPERT SYSTEM UTILISATION .................................................................................................................. 91
5.4APPLICATION OF EXPERT SYSTEM ON SOME OF THE EGYPTIAN OIL PVT SAMPLES ......................................... 93
6.CHAPTER 6 ........................................................................................................................................................ 96
RESULTS AND DISCUSSIONS ................................................................................................................................. 96
6.1 GUIDELINES FOR SELECTING THE APPROPRIATE PVT PROPERTIES BASED ON THE RESULTS OF RELIABILITY ANALYSIS PERFORMED
ON EGYPTIAN OIL SAMPLES ............................................................................................................................................ 96 6.1.1. COMPARISON OF BUBBLE POINT PRESSURE CORRELATIONS ..................................................................................... 96 6.1.2. COMPARISON OF SOLUTION GAS OIL RATIO CORRELATIONS. .................................................................................... 97 6.1.3. COMPARISON OF BUBBLE POINT OIL FORMATION VOLUME FACTOR CORRELATIONS. .................................................... 97 6.1.4. COMPARISON OF UNDER-SATURATED OIL FORMATION VOLUME FACTOR CORRELATIONS. ............................................. 97
X
6.1.5. COMPARISON OF UNDER-SATURATED OIL VISCOSITY CORRELATIONS. ........................................................................ 97 6.1.6. COMPARISON OF GAS SATURATED OIL VISCOSITY CORRELATIONS. ............................................................................ 98 6.1.7. COMPARISON OF THE COEFFICIENT OF UNDER-SATURATED ISOTHERMAL OIL COMPRESSIBILITY CORRELATIONS. ................. 98 6.1.8. COMPARISON OF GAS SATURATED OIL DENSITY CORRELATIONS. ............................................................................. 98 6.1.9. COMPARISON OF UNDER-SATURATED OIL DENSITY CORRELATIONS. .......................................................................... 99 6.2 GUIDELINES FOR SELECTING THE APPROPRIATE PVT PROPERTIES BASED ON RESULTS OF RELIABILITY ANALYSIS PERFORMED ON
WORLDWIDE GAS CONDENSATE SAMPLES .......................................................................................................................... 99 6.2.1. COMPARISON OF GAS COMPRESSIBILITY FACTOR CORRELATIONS. ............................................................................. 99 6.2.2. COMPARISON OF DEW POINT PRESSURE CORRELATIONS. ........................................................................................ 99
7.CHAPTER 7 ...................................................................................................................................................... 100
CONCLUSIONS AND RECOMMENDATIONS ......................................................................................................... 100
7.1 CONCLUSIONS: ................................................................................................................................................ 100 7.2 RECOMMENDATIONS: ....................................................................................................................................... 101
REFERENCES ....................................................................................................................................................... 102
APPENDIX A ....................................................................................................................................................... 114
EMPIRICAL PVT CORRELATIONS USED FOR CORRELATIONS ............................................................................... 114
APPENDIX B ............................................................................................................................................................
ERROR CALCULATIONS DETAILS FOR OIL DATA BASE ......................................................................................... 169
XI
LIST OF TABLES
Table No. Page
Table 4- 1: Data Range for the Egyptian PVT Data ........................................................... 52
Table 4- 2: Reported Input Parameters Ranges for Bubble Point Pressure Correlations 53
Table 4- 3: Reported Input Parameters Ranges for Solution Gas Oil Ratio Correlations . 54
Table 4- 4: Reported Input Parameters Ranges for Under-Saturated Isothermal Oil
Compressibility Correlations ............................................................................................ 55
Table 4- 5: Reported Input Parameters Ranges for Formation Volume Factor Correlations
........................................................................................................................................... 56
Table 4- 6: Reported Input Parameters Ranges for Total Formation Volume factor
Correlations ...................................................................................................................... 57
Table 4- 7: Reported Input Parameters Ranges for under-saturated Oil Viscosity
Correlations ...................................................................................................................... 58
Table 4- 8: Reported Input Parameters Ranges for Bubble Point Oil Viscosity Correlations
........................................................................................................................................... 59
Table 4- 9: Reported Input Parameters Ranges for Dead Oil Viscosity Correlations ....... 60
Table 4- 10: Data Range for the World-Wide PVT Gas Condensate Samples .................. 73
Table 4- 11: Reported Input Parameters Ranges for Dew Point Pressure Correlations .. 74
Table 4- 12: Reported Input Parameters Ranges for Gas Viscosity µg Correlations ........ 75
Table 4- 13: Reported Input Parameters Ranges for Gas Z Factor Correlations .............. 76
Table 4- 14: Reported Input Parameters Ranges for Critical Properties Correlations ..... 77
Table 4- 15: Reported Input Parameters Ranges for Isothermal compressibility of a gas,
cg Correlation .................................................................................................................... 79
Table 4- 16: Reported Input Parameters Ranges for Hydrate temperature Correlations 79
Table 4- 17: Reported Input Parameters Ranges for Bw Correlations ............................. 84
Table 4- 18: Reported Input Parameters Ranges for cw Correlations ............................. 85
XII
Table 4- 19: Reported Input Parameters Ranges for Water density ρw Correlations ..... 86
Table 4- 20: Reported Input Parameters Ranges for methane solubility in brine
Correlations ...................................................................................................................... 87
Table 4- 21: Reported Input Parameters Ranges for Brine viscosity µw Correlations .... 88
XIII
LIST of FIGURES
Figure No. Page Figure 4- 1: Cross-plot between estimated and experimental bubble point pressure, psia.
........................................................................................................................................... 61
Figure 4- 2: Cross-plot between estimated and experimental solution gas-oil ratio,
scf/STB for the range of 0-200 scf/STB. ............................................................................ 62
Figure 4- 3: Cross-plot between estimated and experimental solution gas-oil ratio,
scf/STB for the range of 0-3000scf/STB. ........................................................................... 63
Figure 4- 4: Cross-plot between estimated and experimental bubble point oil formation
volume factor (bbl/STB). ................................................................................................... 64
Figure 4- 5: Cross-plot between estimated and experimental the coefficient of under-
saturated isothermal oil compressibility data, psia -1. ................................................... 65
Figure 4- 6: Cross-plot between estimated and experimental under-saturated oil
viscosity data, cp. ............................................................................................................. 66
Figure 4- 7: Cross-plot between estimated and experimental saturated oil viscosity
data, cp. ............................................................................................................................ 67
Figure 4- 8: Cross-plot between estimated and experimental under saturated oil
formation volume factor, bbl/STB. ................................................................................... 68
Figure 4- 9: Cross-plot between calculated and experimental Z-factor for Pappy method.
........................................................................................................................................... 80
Figure 4- 10: Cross-plot between calculated and experimental dew point pressure of gas
condensate, psia. .............................................................................................................. 81
Figure 4- 11: Cross-plot between estimated and experimental dew point pressure of gas
condensate, psia. .............................................................................................................. 81
Figure 5- 1: PVT expert system utilisation. ...................................................................... 92
Figure 5- 2: An extract of the PVT Expert System database used in selection. ............... 94
Figure 5- 3: An extract of the PVT Expert System output results. ................................... 95
XIV
List of abbreviations
Scf standard cubic feet
Bbl barrels
STB Stock Tank Barrel
PVT Pressure, Volume and Temperature
CVD constant volume depletion
CCE constant composition expansion
Nomenclature
Bo Oil Formation Volume Factor bbl/STB
Rso Solution Gas-oil ratio scf/STB
Pb Bubble point pressure psia
API Gravity of stock tank oil degree
Mc7plus C7 plus molecular weight lb/lb. mole
Bgi Gas formation volume factor bbl/Mscf
Boi Oil formation volume factor Bbl/STB
γgR reservoir gas specific gravity
xc7plus % of C7plus (C7+) -
γg sp separator gas specific gravity in
Rspd
Separator producing gas condensate ratio above the
dew point pressure
scf/STB
ρc7 densityc7plus g/cc
GCR Gas condensate ratio SCF/STB
Gi
Original gas in-place
MMscf
γSTO
The specific gravity of the stock –tank oil
AGP The additional gas produced and related to the mass of
the gas produced from the second separator and the
stock tank.
XV
VEQ The equivalent volume; is the volume of second
separator gas and stock-tank gas plus the volume in
scf that would be occupied by a barrel of stock-tank
liquid if it were gas.
SCF/STB
oAPI API stock tank oil gravity
Mwo Molecular weight of the stock-tank liquid lb/lb. mole
µ Viscosity cp
co oil compressibility psia
-1
γg Gas specific gravity STB
γo Oil specific gravity -
ρr Reduced density -
P System pressure psi
Pci Critical pressure of component i, psi
Pd Dew point pressure psi
Pi Initial reservoir pressure psi
PPc Pseudo-critical pressure psi
PPr Pseudo-reduced pressure -
Pwf Bottom hole flowing pressure psi
Psp Separator Pressure, psia Mscf/D
Tsp Separator temperature ̊F
R Instantaneous gas oil ratio scf/STB
O oil density g/cc
Rs Solution gas oil ratio Mscf/STB
Rsi Initial solution gas oil ratio Mscf/STB
Rv Vaporized oil gas ratio STB/Mscf
Rvi Initial vaporized oil gas ratio STB/Mscf
1:
viscosity of the gas at atmospheric pressure and
reservoir temperature
cp
a0-a15 coefficients of the equations are given in the tables -
So Oil saturation fraction
Swi Initial water saturation fraction
T System temperature °R
Tb Boiling point temperature °R
Tci critical temperature of component i °R
XVI
Tf Formation temperature °R
TPC Pseudo-critical temperature °R
Ppr (Pr): pseudo-reduced pressure of the gas mixture -
Zco 2
Mole fraction of carbon dioxide in reservoir fluid
(gas plus liquid) phases
Fraction
ZH2S
Mole fraction of hydrogen sulfide in reservoir fluid
(gas plus liquid) phases
Fraction
Zi
Mole fraction of component i in reservoir fluid (gas
plus liquid) phases
Fraction
Xi
Mole fraction of component i in reservoir liquid
phase
Fraction
yi
Mole fraction of component i in reservoir liquid
phase
Fraction
Z Single gas phase deviation factor -
Z2p Two phase Z factor -
Zd gas deviation factor at dew point -
Zi gas deviation factor at initial condition -
γg dry gas specific gravity
γw Wet gas specific gravity
γo Specific gravity of the stock-tank liquid
Tpr (Tr): pseudo-reduced temperature of the gas mixture -
μg Gas viscosity cp
ρg Gas density lb/ft3
IAWPS
The International Association for The Properties of
Water and Steam
1
1. CHAPTER 1
INTRODUCTION
Ideally, PVT properties are experimentally measured in the laboratory. When
such direct measurements are not available, PVT correlations from the literature are
often used.
Fundamentally, there are two different types of correlations in literature. The first group
of correlations is developed using randomly selected datasets. We would like to call
such correlations generic correlations. The second group of correlations is developed
using a certain geographical area or a certain types of oil. Correlations using randomly
selected datasets may not be suitable for certain type of oils, or certain geographical
areas. Even though the authors of the generic correlations want to cover a wide range of
data .Such correlations still work better for certain types of oils.
Specialized correlations represent the properties of a certain type of oil or geographical
area (for which they are developed) better than the general purpose correlations.
The best source of oil property data is the laboratory PVT (pressure-volume-
temperature) analysis of a reservoir fluid sample. However, in the absence of
experimentally measured properties of reservoir fluids, these physical properties must be
estimated from correlations.
Many correlations for estimating crude oil PVT properties have been published in the
past 50 years. Most of these correlations yield reasonably accurate results when applied
at the original limitations.
Here our work presents the details of the error statistics for each correlation. For
comparison, error analyses were carried out for this study and for some of the more
frequently used published correlations in the industry.
We believe that the results obtained by using these correlations will improve the use of
material balance calculations as well as the recovery efficiency of a reservoir.
2
A computer simulation program for oil PVT correlations model was written in a
programming language to predict all the properties over a wide range of input data and
also to provide the most appropriate correlation to be used for any reservoir data range
based on the limitations of each correlation which has been mentioned in the literature
with all database of limitations as briefly explained in chapter 4.
In our work Chapter 1 gives a brief introduction about our crude oil, gas and water
properties determination and how the correlation is useful in the petroleum literature.
Chapter 2 is a literature review about the published correlations of oil, gas and water
properties. In order to get reliable results of this work a special care is given to the
limitations of the input parameters of each correlation.
Chapter 3 presents the statement of the problem and objectives of the current study.
Chapter 4 gives an overview about oil correlations and data range for the Egyptian PVT
data and data bank ranges for each published correlation. Also, there are cross-plots
between estimated and experimental properties. Results of reliability analysis were
performed on Egyptian oil samples.
Chapter 4 also presents gas correlations and how it is preferred for the petroleum
science, where data range for the world wide above 119 PVT gas condensate samples
are tested. Also, there are cross-plots between estimated and experimental properties of
gas condensate properties.
In chapter 4 water correlations are considered and how understanding of the properties
of the produced water is very important in reducing the cost of handling the produced
water and increase added value of the produced oil in addition to cost reduction.
Chapter 5 explains in details the development process of the Expert System.
Chapter 6 summarizes the results of reliability analysis performed on Egyptian oil
samples and worldwide gas condensate samples.
3
Chapter 7 summarizes conclusion and recommendation of the evaluation studies of
correlations. As more correlations are developed, the researchers evaluate the previously
published correlations with the new ones. Others carried out studies to select the most
accurate correlation for a particular reservoir in a geographic area.
4
2. CHAPTER 2
LITERATURE REVIEW
In this chapter we present the most popular black oil correlations developed
during the period from 1947 to 2010. The chapter provides the essential background
required for the comparison and listed all ranges of the inputs according to the original
condition of each correlation as published in the original paper.
There have been a number of empirical correlations developed for medium and light
crude oils. However, their applicability is limited to specific oils due to the complex
formulation of the crude oils. Moreover, their applicability to heavy oils is very much in
question. Egbogh1 used the pour point as an additional input parameter for dead oil
viscosity correlations .De Ghetto et al.2
first defined the heavy oils in terms of oAPI
gravity. Later, he divided the heavy oil into two groups: heavy oil(10 < oAPI <22.3)and
extra heavy oil (oAPI <10).Hossain and Sarica
3 mentioned that Lohrenz and Bray also
used the crude oil chemical composition to develop an empirical correlation for oil
viscosity .
Standing 4
,in 1947 used a total of 105 data points on 22 different crude oils from
California to develop his correlations. Lasater 5
, in 1958 presented a bubble point
correlation using 158 measured bubble point data on 137 crude oils from Canada,
Western and Mid-Continental United States and South America. Vasquez and Beggs 6
,in 1989 developed correlations for the solution gas to oil ratio and formation
volume factor using 600 laboratory PVT analysis. Glasso7,
in 1980 used data from 45
oil samples mostly from the North Sea region to develop his correlations. Al-Marhoun8
,in 1988 used 160 bubble point data on 69 Middle Eastern crude samples to
develop a bubble point pressure correlation. Ahmed 9used the combined reported data
of Glasso and Marhoun to develop a correlation for determining the oil formation
volume factor.