Pet ro leum Fract ions
 
C h a r a c t e r i z a t i o n
a n d P r o p e r t i e s o f
P e t r o l e u m F r a c t i o n s
F i rs t Ed i t ion
M. R. R iaz i
Professor of Chemical Engineering
 
L i b r a r y o f C o n g r e s s C a t a l o g i n g - i n - P u b l i c a ti o n D a t a
R i a z i , M . - R .
C h a r a c t e r i z a t i o n a n d p r o p e r t i e s o f p e t r o l e u m f r a c t io n s / M . -R . R i a z i - - 1 s t e d .
p . c m . - - ( A S T M m a n u a l s e r ie s : M N L 5 0 )
A S T M s t o ck n u m b e r : M N L 5 0
I n c l u d e s b i b l i o g r a p h i c a l r e f e r e n c e s a n d i n d e x .
I S B N 0 - 8 0 3 1 - 3 3 6 1 - 8
1 . C h a r a c t e r i z a t i o n . 2 . P h y s i c a l p r o p e r t y e s t i m a t i o n . 3 . P e t r o l e u m f r a c t i o n s - - c r u d e o i l s.
T P 6 9 1 . R 6 4 2 0 0 5
6 6 6 . 5 - - - d c 2 2
2 0 0 4 0 5 9 5 8 6
C o p y r i g h t 9 2 0 0 5 A M E R I C A N S O C I E T Y F O R T E S T I N G A N D M A T E R I A L S , W e s t C o n s h o h o c k en ,
P A . A l l r i g h t s r e s er v e d . T h i s m a t e r i a l m a y n o t b e r e p r o d u c e d o r c o p i e d , i n w h o l e o r i n p a r t, i n a n y
p r i n t e d , m e c h a n i c a l , e l e c t r o n i c , f il m , o r o t h e r d i s t r ib u t i o n a n d s t o r a g e m e d i a , w i t h o u t t h e w r i t t e n
c o n s e n t o f t h e p u b l i s h e r.
P h o t o c o p y R i g h t s
A u t h o r i z a t i o n t o p h o t o c o p y i t e m s f o r i nt e r n a l , p e r s o n a l , o r e d u c a t i o n a l c l a s s r o o m u s e ,
o r t h e i n te r n a l , p e r s o n a l , o r e d u c a t i o n a l c l a s s r o o m u s e o f s p e c i f i c c l i e n t s , i s g r a n t ed b y
t h e A m e r i c a n S o c i e t y f o r T e s t i n g a n d M a t e r i a l s ( A S T M ) p r o v i d e d t h a t t h e a p p r o p r i a t e f e e
i s p a i d t o t h e C o p y r i g h t C l e a r a n c e C e n t e r , 2 2 2 R o s e w o o d D r i v e , D a n v e r s , M A 0 1 9 2 3 ;
T e l: 5 0 8 - 7 5 0 - 8 4 0 0 ; o n l i n e : h t t p : / / w w w . c o p y r i g h t . c o m / .
N O T E : T h i s p u b l i c a ti o n d o e s n o t p u r p o r t t o a d d r e s s a l l o f th e s a f e t y p r o b l e m s a s s o c i a t e d w i t h
i t s u s e . I t i s t h e r e s p o n s i b i l i t y o f t h e u s e r o f t h i s p u b l i c a t i o n t o e s t a b l i s h a p p r o p r i a t e s a f e t y a n d
h e a l t h p r a c t i c e s a n d d e t e r m i n e t h e a p p l i c a b i l it y o f r e g u l a t o r y l i m i t at i o n s p r i o r t o u s e .
P r i n t e d i n P h i l a d e l p h i a , P A
 
P r e f a c e
C h a p t e r 1--Introduction
Nomenclature
1.1.1 Hydrocarbons
1.1.3 Petroleum Fractions and Products
1.2 Types and I mpor tan ce of Physical Properties
1.3 I mportan ce of Petrole um Fluids Characte rization
1.4 Organizat ion of the Book
1.5 Specific Featu res of this Manual
1.5.1 Intr oduct ion of Some Existing Books
1.5.2 Special Features of the Book
1.6 Applications of the Book
1.6.1 Applications in Petrol eum Processing
(Downstream)
(Upstream)
1.7.1 Importa nce and Types of Units
1.7.2 Fundamenta l Units and Prefixes
1.7.3 Units of Mass
1.7.4 Units of Length
1.7.5 Units of Time
1.7.6 Units of Force
1.7.7 Units of Moles
1.7.11 Units of Volume, Specific Volume, and
Molar Volume---The Standard Conditions
1.7.13 Units of Density and Molar Density
1.7.14 Units of Specific Gravity
1.7.15 Units of Composit ion
1.7.16 Units of Energy and Specific Energy
1.7.17 Units of Specific Energy per Degrees
1.7.18 Units of Viscosity and Ki nemat ic Viscosity
1.7.19 Units of Thermal Conductivi ty
1.7.20 Units of Diffusion Coefficients
1.7.21 Units of Surface Tension
1.7.22 Units of Solubility Par ame te r
1.7.23 Units of Gas-to-Oil Ratio
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19
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21
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23
23
24
24
1.7.24.1 Gas Const ant
1.7.24.2 Other Numerical Constants
1.7.25 Special Units for the Rates a nd Amounts of
Oil and Gas
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27
C h a p t e r 2 - - C h a r a c t e r i z a t i o n a n d P r o p er t ie s o f P u r e
H y d r o c a r b o n s
Nomenclature
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
2.1.7
2.1.8
2.1.9
2.1.10
2.1.11
2.1.12
2.1.13
2.1.14
2.1.15
2.1.16
2.1.17
Gravity
Acentric Factor
Vapor Pressure
Kinematic Viscosity
Flash Point
2.2 Data on Basic Properties of Selected Pure
Hydrocarbons
2.2.3 Additional Data on Properties of Heavy
Hydrocarbons
for Hydrocar bon Properties
Hydrocar bon Systems
Hydrocarbons
Nonhydroc arbon Systems
Specific Gravity
2.4.1.1 Riaz i-Daubert Methods
2.4.1.5 Goossens Correla tion
2.4.2.2 Soreide Correlation
2.4.3.1 Riazi- Dauber t Methods
2.5 Prediction of Critical Properties and Acentric
Factor
Pressure
2.5.1.2 API Methods
2.5.1.3 Lee-Kesler Method
2.5.1.4 Cavett Method
2.5.1.5 Twu Metho d fo r To, Pc, Vc, and M
2.5.1.6 Winn-Mobil Method
2.5.1.7 Tsonopoulos Correlations
2.5.2.2 Hall-Yarborough Method
2.5.2.3 API Method
2.5.4 Prediction of Acentric Factor
2.5.4.1 Lee-Kesler Meth od
2.6 Predic tion o f Density, Refractive Index, CH Weight
Ratio, and Freezing Point
2.6.2 Prediction of Refractive Index
2.6.3 Prediction of CH Weight Ratio
2.6.4 Prediction of Freezing/Melting Point
2.7 Prediction of Kinematic Viscosity at 38
and 99~
Characterization Methods
Method
Molecular Weight
Critical Properties
Acentric Factor and Other Properties
2.10 Conclusions and Recommen dations
2.11 Problems
References
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C h a p t er 3 - - C h a r a c t e r i z a ti o n o f P e t r o l e u m F r a c t i o ns
Nomenclature
Petroleum Fractions
3.1.1.1 ASTM D86
3.1.1.3 Simula ted Distillation by Gas
Chromatography
3.1.2 Density, Specific Gravity, and API Gravity
3.1.3 Molecular Weight
3.1.5.3 PNA Analysis
3.2.1 Average Boiling Points
3.2.2.1 Riaz i-Daubert Method
at Reduced Pressures
of Various Distillation Curves
3.3.1 Matrix of Pseudocomponents Table
3.3.2 Nar row Versus Wide Boiling Range
Fractions
Mixtures)
Mixtures)
Properties, a nd Acentric Factor
3.3.6 Est ima tion of Density, Specific Gravity,
Refractive Index, and Kinemat ic Viscosity
3.4 General Procedure for Properti es of Mixtures
3.4.1 Liquid Mixtures
3.4.2 Gas Mixtures
Fractions
3.5.1.1 Charac teriz ation Paramete rs for
Molecular Type Analysis
3.5.1.3 API Method
3.5.1.4 n-d-M Method
Contents
Contents
3.6.1 Properties Related to Volatility
3.6.1.1 Reid Vapor Pressure
3.6.1.3 Flash Point
3.6.6 Cetane Number and Diesel Index
3.6.7 Octane Num ber
3.8 Mini mum Laboratory Data
3.9 Analysis of Laboratory Data and De velopment
of Predictive Methods
3.11 Problems
C h a p t e r A
C h a r a c t e r i z a t io n o f R e s e r v o i r F l u i d s a n d
C r u d e Oils
Nomenclature
Assays
4.1.2 Crude Oil Assays
Systems
4.3 Charac teri zation and Properti es of Single Carbon
Numbe r Groups
Hydrocarbon-plus Fractions
4.5.4 General ized Distributi on Model
4.5.4.1 Versatile Correla tion
Proposed Generalized Distribution
Hydrocarbon-Plus Fractions
Subfractions
Using Bulk Propertie s
4.6.1 Splitting Sche me
4.6.1.2 Carbon Number Range Approach
4.6.2 Lumpi ng Sche me
4.7 Continuous Mixture Characterization Approach
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184
185
186
186
187
Reservoir Fluids
4.8.1 General Approach
4.8.2 Esti mati on of Sulfur Content of a Crude Oil
4.9 Conclusions and Recomme ndatio ns
4.10 Problems
References
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190
191
192
193
194
C h a p t er 5 m P V T R e l a t io n s a n d E q u a t i o n s o f S t a t e
Nomenclature
5.2 PVT Relations
5.5.1 Four C ommon Cubic Equations (vdW, RK,
SRK, and PR)
5.5.3 Volume Translation
5.5.5 Application to Mixtures
5.6.2 Modified Benedict -Webb-Rubi n Equat ion
of State
Modifications
Liquids--Rackett Equation
Saturated Liquids
Fractions
5.10 S umm ary and Conclusions
5.11 Problems
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C h a p t er 6 - - - T h e r m o d y n a m i c R e l a t io n s f o r P r o p e rt y E s t i m a t i o n s
Nomenclature
Relations
Fundamental Relations
Functions
Components
6.2 Generalized Correlations for Calculation of
Therm odynam ic Properties
6.4 Therm odynam ic Properties of Mixtures
6.4.2 Properties of Mixtures--Pro perty Change
Due to Mixing
6.5 Phase Equilibria of Pure Component s--Conc ept
of Saturation Pressure
of Basic Properties
Activity, Activity Coefficient, and Chemical
Potential
Equations of State
6.6.4 Calculation of Fugacity of Pure Gases and
Liquids
6.6.6 Calculation of Fugaci ty of Solids
6.7 General Method for Calculation of Properties of
Real mixtures
Mixtures
Liquids
Equilibria Relations
Liquids--Henry's Law
6.8.3 Solid-Liquid Equil ibria --Soli d Solubility
6.8.4 Freezing Point Depression and Boiling Point
Elevation
6.9 Use of Velocity of Sound in Pred iction of Fluid
Properties
of State
of Sound Data
6.9.2.1 Virial Coefficients
Parameters
Property Estimation
6.11 Problems
References
Chapter 7 - -A ppl icat ions : Es t imat ion o f Th ermoph ys ica l
Propert ies
Thermophysical Properties of Petrol eum Fractions
and Defined Hydrocarbon Mixtures
7.3 Vapor Pressure
7.3.1 Pure Components
Correlations
7.3.3.1 Analytical Methods
Pressure of Petroleum Products
7.4 Thermal Properties
Vaporization
7.5 Summary and Recommendations
References
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306
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312
313
314
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321
324
326
327
328
Ch apter 8mA ppHcat ions : Es t imat ion o f T ransport Properti e s
Nomenclature
8.1.1 Viscosity of Gases
8.1.2 Viscosity of Liquids
8.3 Diffusion Coefficients
8.3.3 Diffusivity of Gases and Liquids at High
Pressures
Systems
8.4 Interrelat ionship Among Transport Properties
8.5 Measurement of Diffusion Coefficients in Reservoi r
Fluids
8.8 Problems
References
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339
339
342
345
346
347
348
350
350
351
354
356
356
358
361
362
362
Chapter 9 - -Appl ica t ions : Phase Equi l ibr ium Calcu la t ions
Nomenclature
9.2 Vapor-Liquid Equilibrium Calculations
9.2.1 Flash Calculations--Gas-to-Oil Ratio
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368
370
C O N T E N T S x v
9 .2 .3 G e n e r a t i o n o f P - T D i a g r a m s - - T r u e C r i ti c a l
P r o p e r t i e s
9 .3 V a p o r - L i q u i d - S o l i d E q u i l i b r i u m - - S o l i d
P r e c i p i t a t i o n
9 .3 .1 N a t u r e o f H e a vy C o m p o u n d s , M e c h a n i s m o f
t h e i r P r e c i p i ta t i o n , a n d P r e v e n t i o n M e t h o d s
9 .3 .2 W a x P r e c i p i t a t i o n - - S o l i d S o l u t i o n M o d e l
9 . 3 . 3 W a x P r e c i p i t a t i o n : M u l t i s o l i d - P h a s e
M o d e l ~ C a l c u l a t i o n o f C l o ud P o i n t
9 .4 A s p h a k e n e P r e c i p it a t io n : S o l i d - L i q u i d E q u i l i b r i u m
9 .5 V a p o r - S o li d E q u i l i b ri u m - - H y d r a t e F o r m a t i o n
9 .6 A p p l i c a ti o n s : E n h a n c e d O i l R e c o v e r y - - E v a l u a t i o n
o f G a s I n j e c t i o n P r o j e c t s
9 .7 S u m m a r y a n d R e c o m m e n d a t i o n s
9 . 8 F i n a l W o r d s
9 . 9 P r o b l e m s
R e f e r e n c e s
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I n d e x
3 9 7
4 0 1
F o r e w o r d
TH IS PUBLICATION,Characterization and Properties of Petroleum Fractions, w a s s p o n s o r e d
b y A S T M C o m m i t t e e D 0 2 o n P e t r o l e u m F u e l s a n d L u b r i c a n t s . T h e a u t h o r i s M . R . R i a z i,
P r o f e s s o r o f C h e m i c a l E n g i n e e r i n g , K u w a i t U n i v e r si ty , S a f a t, K u w a i t . T h i s p u b l i c a t i o n
i s M a n u a l 5 0 o f A S T M ' s m a n u a l s e r i e s .
xvii
P r e f a c e
Scien t is t s do no t be long to any par t icular country , ideology, or re l ig ion, they belong
t o t he w o r l d c o m m u n i t y
THE FIELDOF P e t r o l e u m C h a r a c t e r i z a t i o n a n d P h y s i c a l P r o p e r t i e s h a s r e c e i v e d s i g n if i c an t
a t t e n ti o n i n r e c e n t d e c a d e s w i t h t h e e x p a n s i o n o f c o m p u t e r s i m u l a t o r s a n d a d v a n c e d
a n a l y t i c a l to o l s a n d t h e a v a i l a b i l it y o f m o r e a c c u r a t e e x p e r i m e n t a l d a t a . A s a re s u l t o f
g l o b a l i z a ti o n , s t r u c t u r a l c h a n g e s a r e t a k i n g p l a c e in t h e c h e m i c a l a n d p e t r o l e u m i n d u s -
t ry . E n g i n e e r s w o r k i n g i n t h e s e i n d u s t r i e s a r e i n v o l v e d w i t h p r o c e s s s i m u l a t o r s t o d e s i g n
a n d o p e r a t e v a ri o u s u n i ts a n d e q u i p m e n t . N o w a d a y s , a l a rg e n u m b e r o f p r o c e s s s i m u la -
t o r s a r e b e in g p r o d u c e d t h a t a r e e q u i p p e d w i t h a v a r i e ty o f t h e r m o d y n a m i c m o d e l s a n d
c h o i c e o f p r e d i c t iv e m e t h o d s f o r t h e p h y s i c a l p r o p e r t i e s . A p e r s o n f a m i l i a r w i t h d e v e l -
o p m e n t o f s u c h m e t h o d s c a n m a k e a p p r o p r i a t e u s e o f t h e se s i m u l a t o r s s a v i n g b il li o n s
o f d o l la r s i n c o s t s i n i n v e s t m e n t , d e s i g n , m a n u f a c t u r e , a n d o p e r a t i o n o f v a r i o u s u n i t s
i n th e s e i n d u s t ri e s . P e t r o l e u m i s a c o m p l e x m i x t u r e o f t h o u s a n d s o f h y d r o c a r b o n c o m -
p o u n d s a n d i t is p r o d u c e d f r o m a n o i l w e l l in a f o r m o f r e s e r v o i r fl u id . A r e s e r v o i r f lu i d is
c o n v e r t e d t o a c r u d e o i l t h r o u g h s u r f a c e s e p a r a t i o n u n i t s a n d t h e n t h e c r u d e i s s e n t t o a
r e f in e r y to p r o d u c e v a r i o u s p e t r o l e u m f r a c ti o n s a n d h y d r o c a r b o n f u el s s u c h a s k e r o s e n e ,
g a s o l in e , a n d f u e l o i l. S o m e o f t h e r e f i n e ry p r o d u c t s a r e t h e f e e d t o p e t r o c h e m i c a l p l a n t s .
M o r e t h a n h a l f o f w o r l d e n e r g y s o u rc e s a r e f r o m p e t r o l e u m a n d p r o b a b l y h y d r o c a r b o n s
w i ll r e m a i n t h e m o s t c o n v e n i e n t a n d i m p o r t a n t s o u r c e o f e n e r g y a n d a s a r a w m a t e r i a l
f o r t h e p e t r o c h e m i c a l p l a n t s a t l e a s t t h r o u g h o u t t h e 2 1 st c e n t u ry . O t h e r f o s si l ty p e f u -
e l s s u c h a s c o a l l i qu i d s a r e a l s o m i x t u r e s o f h y d r o c a r b o n s a l t h o u g h t h e y d i f f e r i n t y p e
w i t h p e t r o l e u m o il s. F r o m 1 9 70 t o 2 0 0 0, t h e s h a r e o f M i d d le E a s t i n t h e w o r l d c r u d e o i l
r e s e r v e s r a i s e d f r o m 5 5 t o 6 5 % , b u t t h i s s h a r e i s e x p e c t e d t o r i s e e v e n f u r t h e r b y 2 0 1 0 -
2 0 2 0 w h e n w e n e a r t h e p o i n t w h e r e h a l f o f oi l r e s e r v e s h a v e b e e n p r o d u c e d . T h e w o r l d
i s n o t r u n n i n g o u t o f o i l y e t b u t t h e e r a o f c h e a p o i l i s p e r h a p s n e a r t h e e n d . T h e r e f o r e ,
e c o n o m i c a l u s e o f t he r e m a i n i n g o il a n d t r e a t m e n t o f h e a v y o il s b e c o m e i n c re a s in g l y
i m p o r t a n t . A s it is d i s c u s s e d i n C h a p t e r 1 , u s e o f m o r e a c c u r a t e p h y s i c a l p r o p e r t i e s f o r
p e t r o l e u m f r a c t i o n s h a s a d i r e c t a n d s i g n i f i c a n t i m p a c t o n e c o n o m i c a l o p e r a t i o n a n d
d e s i g n o f p e t r o l e u m p r o c e s s i n g a n d p r o d u c t i o n u n i t s w h i c h i n t u r n w o u l d r e s u l t in a
s i g n i fi c a n t s a v i n g o f e x i s t in g p e t r o l e u m r e s e r v e s.
O n e o f th e m o s t i m p o r t a n t t a s k s i n p e t r o l e u m r e f in i n g a n d r e l a t e d p r o c e s s e s i s th e
n e e d f o r r e li a b le v a l u e s o f t h e v o l u m e t r i c a n d t h e r m o d y n a m i c p r o p e r t i e s f o r p u r e h y -
d r o c a r b o n s a n d t h e i r m i x tu r e s . T h e y a re i m p o r t a n t i n t h e d e s i g n a n d o p e r a t i o n o f a lm o s t
e v e r y p i e c e o f p r o c e s s i n g e q u i p m e n t . R e s e r v o i r e n g in e e r s a n a l y z e P V T a n d p h a s e b e h a v -
i o r o f r e s e r v o i r f lu i d s to e s t i m a t e t h e a m o u n t o f o i l o r g a s i n a r e s e rv o i r , to d e t e r m i n e a n
o p t i m u m o p e r a t i n g c o n d i t i o n i n a s e p a r a t o r u n i t , o r t o d e v e l o p a r e c o v e r y p r o c e s s f o r
a n o i l o r g a s f ie ld . H o w e v e r, th e m o s t a d v a n c e d d e s i g n a p p r o a c h e s o r t h e m o s t s o p h i s t i -
c a t e d s i m u l a t o rs c a n n o t g u a r a n t e e t h e o p t i m u m d e s i g n o r o p e r a t io n o f a u n it i f r e q u i re d
i n p u t p h y s i c a l p r o p e r t i e s a r e n o t a c c u r a t e . A p r o c e s s t o e x p e r i m e n t a l l y d e t e r m i n e t h e
v o l u m e t r i c , t h e r m o d y n a m i c , a n d t r a n s p o r t p r o p e r t i e s f o r a l l t h e i n d u s t r i a l l y i m p o r t a n t
m a t e r i a l s w o u l d b e p r o h i b i t i v e i n b o t h c o s t a n d t i m e ; i n d e e d i t c o u l d p r o b a b l y n e v e r
b e c o m p l e t e d . F o r th e s e r e a s o n s a c c u r a t e e s t i m a t i o n s o f t h e s e p r o p e r t i e s a r e b e c o m i n g
i n c r e a s i n g l y i m p o r t a n t .
C h a r a c t e r i z a t i o n f a c t o r s o f m a n y t y p e s p e r m e a t e t h e e n t i r e f ie l d o f p h y s ic a l , t h e r-
m o d y n a m i c , a n d t r a n s p o r t p r o p e r t y p r e d i c t i o n . A v e r a g e b o i l i n g p o i n t s , s p e c if i c g r a vi ty ,
m o l e c u l a r w e i g h t , c r i t i c a l t e m p e r a t u r e , c r i t i c a l p r e s s u r e , a c e n t r i c f a c to r , r e f r a c t i v e i n d e x ,
a n d c e r t a i n m o l e c u l a r t y p e a n a l y s is a r e b a s i c p a r a m e t e r s n e c e s s a r y to u t i li z e m e t h o d s
o f c o r r e l a t i o n a n d p r e d i c t i o n o f t h e t h e r m o p h y s i c a l p r o p e r t i e s . F o r c o r r e l a t i n g p h y s i -
c a l a n d t h e r m o d y n a m i c p r o p e r ti e s , m e t h o d s o f c h a ra c t e r iz i n g u n d e f i n e d m i x t u r e s a r e
x i x
x x P R E F A C E
necessary to provide input data. It could be imagined that the best m ethod o f character-
izing a mixture is a complete analysis. However, becaus e of the complexi ty of undefined
mixtures, complete analyses are usually impossible and, at best, inconvenient. A predic-
tive method to determine the composition or am ount of sulfur in a hydroc arbon fuel is
vital to see if a prod uct meets specifications set by the govern ment or other authorities
to protect the environment.
My first interaction with physical properties of petr oleum fluids was at the time that
I was a graduate student at Penn State in the late 70s working on a project related to
enhanced oil recovery for my M.S. thesis when I was looking for methods of estimation
of properties of petroleum fluids. It was such a need and my personal interest that
later I joined the ongoing API project on thermodynamic and physical properties of
petroleum fractions to work for my doctoral thesis. Since that time, propert y estimation
and char acterization of various petroleum fluids has remained one of my main areas of
research. Later in the mid-80s I rejoined Penn State as a faculty member and I continued
my work with the API which resulted in development of methods for several chapters
of the API Technical Data Book. Several years later in late 80s, I continued the work
while I was working at the Norwegian Institute of Technology (NTH) at Trondheim
where I developed some characterization techniques for heavy petroleum fractions as
well as measuring methods for some physical properties. In the 90s while at Kuwait
University I got the opportunity to be in direct contact with the oil companies in the
region throug h research, consultation, and co nducting special courses for the industry.
My associati on with the University of Illinois at Chicago in early 90s was helpful in the
development of equations of state based on velocity of sound. The final revision of the
book was completed when I was associated with the University of Texas at Austin and
McGill University in Montreal durin g m y leave from Kuwa it University.
Characterization methods and estimating techniques presented in this book have been
published in various international journals or technical handbooks and included in
many com mercial softwares and process simulators. They have also been presented as
seminars in different oil companies, universities, and research centers worldwide. The
major characteristics of these methods are simplicity, generality, accuracy, and avail-
ability of input parameters. Many of these methods have been developed by utilizing
some scientific fundamentals and combining them with a broad experimental data set
to generate semi-theoretical or semi-empirical correlations. Some of these methods have
been in use by the petroleum industry and r esearch centers worldwide for the past two
decades.
Part of the materials in this book were prepared when I was teaching a graduate course
in applied thermodynamics in 1988 while at NTH. The materials, mainly a collection of
technical papers, have been continuously updated and rearr anged to the present time.
These notes have also been used to co nduc t industrial cou rses as well as a course on fluid
properties in chemical and petroleum engineering. This book is an expansion with com-
plete revision and rewr iting of these notes. The ma in objective of this boo k is to present
the fundamentals and practice of estimating the physical and thermodynamic proper-
ties as well as characterization methods for hydrocarbons, petroleum fractions, crude
oils, reservo ir fluids, and natura l gases, as well as coal liquids. However, the emp hasis is
on the liquid petrol eum fractions, as properties of gases are generally calculated more
accurately. The book will emphasize manual calculations with practical problems an d
examples but also wilI provide good understanding of techniques used in c ommercial
software packages for property estimations. Various methods and correlations developed
by different researchers com monl y used in the literature are presented with necessary
discussions and recommendations.
My original goal and objective in writing this book was to provide a reference for the
petroleum industry in both processing and production. It is everyone's experience that in
using thermodyn amic simulators for process design and equipment, a large numbe r of
options is provided to the user for selection of a method to characterize the oil or to get
an es timate of a physical property. This is a difficult choice for a user of a simulator, as
the results of design calculations significantly rely on the method c hose n to estimate the
properties. One of my goals in writing this bo ok was to help users of simulators overcome
this burden . However, the book is written in a way that it can also be used as a textb ook
for graduate or senior undergraduate students in chemical, petroleum, or mechanical
engineering to understand the significance of characterization, property estim ation and
 
PREFACE xxi
m e t h o d s o f t h e i r d e v e l o p m e n t . F o r t h i s p u r p o s e a s e t o f p r o b l e m s i s p r e s e n t e d a t t h e
e n d o f e a c h c h a p t e r . T h e b o o k c o v e r s c h a r a c t e r i z a t i o n a s w e ll a s m e t h o d s o f e s t im a t i o n
o f t h e r m o d y n a m i c a n d t r a n s p o r t p r o p e r t i e s o f v a ri o u s p e t r o l e u m f lu i ds a n d p r o d u c t s. A
g r e a t e m p h a s i s i s g i v e n t o t r e a t m e n t o f h e a v y f r a c t i o n s t h r o u g h o u t t h e b o o k . A n e f f o r t
w a s m a d e t o w r i te t h e b o o k i n a w a y t h a t n o t o n l y w o u l d b e u s e f u l f o r t h e p r o f e s s i o n -
a l s i n th e f i el d , b u t w o u l d a l s o b e e a s i ly u n d e r s t a n d a b l e t o t h o s e n o n - e n g i n e e r s s u c h a s
c h e m i s t s , p h y s i c is t s , o r m a t h e m a t i c i a n s w h o g e t in v o l v e d w i t h t h e p e t r o l e u m i n d u s t r y .
T h e word properties i n th e t i tl e r e fe r s t o t h e r m o d y n a m i c , p h y s i c a l , a n d t r a n s p o r t p r o p e r -
t ie s . P r o p e r t i e s r e l a t e d t o t h e q u a l i t y a n d s a f e t y o f p e t r o l e u m p r o d u c t s a r e a l s o d i s c u s s e d .
O r g a n i z a t i o n o f t h e b o o k , i ts u s e s, a n d i m p o r t a n c e o f t h e m e t h o d s a r e d i s c u s s e d i n d e t a il
i n C h a p t e r 1 . I n t r o d u c t i o n o f s i m i l a r b o o k s a n d t h e n e e d f o r t h e p r e s e n t b o o k a s w e ll a s
i t s a p p l i c a t i o n i n t h e i n d u s t r y a n d a c a d e m i a a r e a l s o d i s c u s s e d i n C h a p t e r 1 . E a c h c h a p -
t e r b e g i n s w i t h n o m e n c l a t u r e a n d e n d s w i t h t h e r e f e r e n c e s u s e d i n t h a t c h a p t e r . E x e r c is e
p r o b l e m s i n e a c h c h a p t e r c o n t a i n a d d i t i o n a l i n f o r m a t i o n a n d m e t h o d s . M o r e s p e ci fi c
i n f o r m a t i o n a b o u t e a c h c h a p t e r a n d i t s c o n t e n t s a r e g i v e n i n C h a p t e r 1 . A s G o e t h e
s a id , " T h in g s w h i c h m a t t e r m o s t m u s t n e v e r b e a t t h e m e r c y o f t h in g s w h i c h m a t t e r
l e a s t . "
I a m i n d e b t e d t o m a n y p e o p l e e s p e c i a l ly t e a c h e r s, c o l l e a g u e s , fr i e n d s , s tu d e n t s , a n d ,
a b o v e a ll , m y p a r e n t s , w h o h a v e b e e n s o h e l p f u l t h r o u g h o u t m y a c a d e m i c l if e. I a m p a r t i c -
u l a r l y t h a n k f u l t o T h o m a s E . D a u b e r t o f P e n n s y l v a n i a S t a te U n i v e r s i t y w h o i n t r o d u c e d
t o m e t h e f i e ld o f p h y s i c a l p r o p e r t i e s a n d p e t r o l e u m c h a r a c t e r i z a t i o n i n a v e r y c l e a r a n d
u n d e r s t a n d a b l e w a y . L i k e w is e , I a m t h a n k f u l t o F a r h a n g S h a d m a n o f t h e U n i v e r s i t y o f
A r i z o n a w h o f o r th e f i r s t t i m e i n t r o d u c e d m e t o t h e f ie l d o f c h e m i c a l e n g i n e e r i n g r e -
s e a r c h d u r i n g m y u n d e r g r a d u a t e s t u d ie s . T h e s e t w o i n d iv i d u a l s h a v e b e e n s o in f l u e n ti a l
i n s h a p i n g m y a c a d e m i c l i fe a n d I a m s o in d e b t e d t o t h e m f o r th e i r h u m a n c h a r a c t e r s
a n d t h e i r s c i en t if i c sk i ll s. I h a v e b e e n f o r t u n a t e t o m e e t a n d t a l k w i t h m a n y s c i e n t is t s a n d
r e s e a r c h e r s f r o m b o t h t h e o i l i n d u s tr y a n d a c a d e m i a f r o m a r o u n d t h e w o r l d d u r in g t h e
l a s t t w o d e c a d e s w h o s e t h o u g h t s a n d i d e a s h a v e i n m a n y w a y s b e e n h e l p fu l i n s h a p i n g
t h e b o o k .
I a m a l s o g r a t e f u l to t h e i n s t i t u ti o n s , r e s e a r c h c e n t e r s , a n d o i l c o m p a n i e s t h a t I h a v e
b e e n a s s o c i a t e d w i t h o r t h a t h a v e i n v i t e d m e f o r l e c t u r i n g a n d c o n s u l t a t io n . T h a n k s t o
K u w a i t U n i v e r s it y a s w e ll a s K u w a i t P e t r o l e u m C o r p o r a t i o n ( K P C ) a n d K N P C , m a n y o f
w h o s e e n g i n e e r s I d e v e l o p e d w o r k i n g r e l a t i o n s w i t h a n d h a v e b e e n h e l p f u l i n e v a l u a t i o n
o f m a n y o f th e e s t i m a t i n g m e t h o d s t h r o u g h o u t t h e y e a r s . I a m t h a n k f u l t o a l l s c i e n ti s t s
a n d r e s e a r c h e r s w h o s e w o r k s h a v e b e e n u s e d i n t h is b o o k a n d I h o p e t h a t a l l h a v e
b e e n c o r r e c t l y a n d a p p r o p r i a t e l y c i te d . I w o u l d b e h a p p y t o r e c e i v e t h e i r c o m m e n t s a n d
s u g g e s t i o n s o n t h e b o o k . F i n a n c i a l s u p p o r t f r o m o r g a n i z a t i o n s s u c h a s A P I , N S F , G PA ,
G R I , S I N T E E P e t r o f i n a E x p l o r a t i o n N o r w a y , N S E R C C a n a d a , K u w a i t U n i v e r s i t y , a n d
K F A S t h a t w a s u s e d f o r m y r e s e a r c h w o r k o v e r t h e p a s t t w o d e c a d e s i s a l s o a p p r e c i a t e d .
I a m g r a t e f u l t o A S T M f o r p u b l i s h i n g t h i s w o r k a n d p a r t i c u l a r l y t o G e r o g e T o t t e n w h o
w a s t h e f i rs t to e n c o u r a g e m e t o b e g i n w r i t i n g t h i s b o o k . H i s a d v i c e, i n t e re s t , s u p p o r t ,
a n d s u g g e s t i o n s t h r o u g h t h e l o n g y e a r s o f w r i t i n g t h e b o o k h a v e b e e n e x t r e m e l y h e l p f u l
i n c o m p l e t i n g t h i s p ro j e c t . T h e i n t r o d u c t o r y c o m m e n t s f r o m h i m a s w e l l a s t h o s e f r o m
P h i li p T . E u b a n k a n d J o s 6 L u i s P e f i a D i e z f o r t h e b a c k c o v e r a r e a p p r e c i a t e d . I a m a l s o
g r a t e f u l t o t h e f o u r u n a n i m o u s r e v i e w e r s w h o t i r e l e ss l y r e v i e w e d t h e e n t i r e a n d l e n g t h y
m a n u s c r i p t w i t h t h e i r c o n s t ru c t i ve c o m m e n t s a n d s u g g e st i on s w h i c h h a v e b e e n r e f le c t ed
i n th e b o o k . T h a n k s a l s o t o K a t h y D e r n o g a , t h e p u b l i s h i n g m a n a g e r a t A S T M , w h o w a s
a l w a y s c o o p e r a t iv e a n d r e a d y t o a n s w e r m y q u e s t io n s a n d p r o v i d e d m e w i t h n e c e s s a r y
i n f o r m a t i o n a n d t o o l s d u r in g t h e p r e p a r a t i o n o f t h is m a n u s c r i p t . H e r e n c o u r a g e m e n t s
a n d a s s i s t a n c e w e r e q u i t e u s e f u l i n p u r s u i n g t h i s w o r k . S h e a l s o w a s h e l p f u l i n t h e d e -
s i g n o f t h e f r o n t a n d b a c k c o v e r s o f t h e b o o k a s w e l l a s p r o v i d i n g e d i t o r ia l s u g g e s t i o n s .
I a m t h a n k f u l t o R o b e r t a S t o r e r a n d J o e E r m i g i o t t i f o r t h e i r e x c e ll e n t j o b o f e d i t in g a n d
u p d a t i n g t h e m a n u s c r i p t . C o o p e r a t i o n o f o t h e r A S T M s t a ff , e s p e c i a l ly M o n i c a S i p e r k o ,
C a r l a J . F a l c o , a n d M a r s h a F i r m a n i s h i g h l y a p p r e c i a t e d . T h e a r t w o r k a n d m o s t o f
t h e g r a p h s a n d f i g u re s w e r e p r e p a r e d b y K h a l e d D a m y a r o f K u w a i t U n i v e r s it y a n d h i s
e f f o r ts f o r th e b o o k a r e a p p r e c i a t e d . I a l s o s i n c e r e ly a p p r e c i a t e t h e p u b l i s h e r s a n d t h e
o r g a n i z a t i o n s t h a t g a v e t h e i r p e r m i s s i o n s t o i n c lu d e s o m e p u b l i s h e d m a t e r i a l s , i n p a r ti c -
u l a r A P I , A C S , A I C h E , G P A , E l s e v i e r ( U . K . ), e d i t o r o f O i l & G a s J . , M c G r a w - H i l l , M a r c e l
a n d D e k k e r, W i le y , S P E , a n d T a y l o r a n d F r a n c i s . T h a n k s t o t h e m a n a g e r a n d p e r s o n n e l
 
xxii PREFACE
m o s t i m p o r ta n t ly , I m u s t e x p r e s s m y a p p r e c i a t i o n a n d t h a n k s t o m y f a m i l y w h o h a v e
b e e n h e l p f u l a n d p a t i e n t d u r i n g a l l t h e s e y e a r s a n d w i t h o u t w h o s e c o o p e r a t i o n , m o r a l
s u p p o r t , u n d e r s ta n d i n g , a n d e n c o u r a g e m e n t t h i s p r o j e c t co u l d n e v e r h a v e b e e n u n d e r-
t a k e n . T h i s b o o k i s d e d i c a t e d t o m y f a m i ly , p a r e n t s , t e a c h e r s , a n d t h e w o r l d s c i en t if i c
c o m m u n i t y .
M . R . R i a z i
 
I n t roduct ion
N O M E N C L A T U R E
A P I A P I g r a v i t y
A % P e r c e n t o f a r o m a t i c s i n a p e t r o l e u m
f r a c t i o n
D D i f f u s i o n c o e f f i c i e n t
C H C a r b o n - t o - h y d r o g e n w e i g h t r a t io
d L i q u i d d e n s i t y a t 2 0 ~ a n d 1 a t m
K w W a t s o n K f a c t o r
k T h e r m a l c o n d u c t i v i t y
Ki E q u i l i b ri u m r a t io o f c o m p o n e n t i i n
a m i x t u r e
l o g1 0 L o g a r i t h m o f b a s e l 0
I n L o g a r i t h m o f b a s e e
M M o l e c u l a r w e i g h t
N min M i n i m u m n u m b e r o f t h e o re t i ca l p la t e s
i n a d i s t i ll a t io n c o l u m n
N % P e r c e n t o f n a p h t h e n e s i n a p e t r o l e u m
f r a c t i o n
n S o d i u m D li n e r e f r a c t iv e i n d e x o f l i q u id
a t 2 0 ~ a n d 1 a t rn , d i m e n s i o n l e s s
n N u m b e r o f m o l e s
P P r e s s u r e
P c C r i t i c a l p r e s s u r e
p sa t V a p o r ( s a t u r a t i o n ) p r e s s u r e
P % P e r c e n t o f p a r a f f i n s i n a p e t r o l e u m
f r a c t i o n
R U n i v e r s a l g a s c o n s t a n t
R i R e f r a c t i v i t y i n t e r c e p t
S G S p e c i f i c g r a v i t y a t 1 5 .5 ~ ( 6 0 ~
S U S S a y b o l t U n i v e r s a l S e c o n d s ( u n i t o f
S % W e i g h t % o f s u l f u r i n a p e t r o l e u m
f r a c t i o n
T T e m p e r a t u r e
T b B o i l i n g p o i n t
T c C r i t ic a l t e m p e r a t u r e
TF F l a s h p o i n t
Tp P o u r p o i n t
TM M e l t i n g ( fr e e z i n g p o i n t ) p o i n t
V V o l u m e
Xm M o l e f r a c t i o n o f a c o m p o n e n t i n
a m i x t u r e
Xv V o l u m e f r a c ti o n o f a c o m p o n e n t i n
a m i x t u r e
Xw W e i g h t f r a c t i o n o f a c o m p o n e n t i n a
m i x t u r e
y M o l e f r a c t i o n o f a c o m p o n e n t in a v a p o r
p h a s e
1
G r e e k L e t t er s
R e l a t i v e v o l a t i l i t y
~0 F u g a c i t y c o e f f i c i e n t
a~ A c e n t r i c f a c t o r
S u r f a c e t e n s i o n
p D e n s i t y a t t e m p e r a t u r e T a n d p r e s s u r e P
/ ~ V i s c o s i t y
v K i n e m a t i c v i s c o s i ty
A c r o n y m s
A P I - T D B A m e r i c a n P e t r o l e u m In s t i t u t e - T e c h n i c a l D a t a
B o o k
b b l B a r r e l
G O R G a s - t o - o il r a t i o
I U PA C I n t e r n a t i o n a l U n i o n o f P u r e a n d A p p l ie d C h e m -
i s t r y
P N A P a r a ff i n , n a p h t h e n e , a r o m a t i c c o n t e n t o f a
p e t r o l e u m f r a c ti o n
S C S t a n d a r d c o n d i t i o n s
s c f S t a n d a r d c u b i c f e e t
s t b S t o c k t a n k b a r r e l
S T O S t o c k t a n k o i l
S T P S t a n d a r d t e m p e r a t u r e a n d p r e s s u r e
I N T H I S I N T R O D U C T O R Y C H A P T E R , f i r s t t h e n a t u r e o f p e t r o l e u m
f l u id s , h y d r o c a r b o n t y p e s , r e s e r v o i r f l u id s , c r u d e o i ls , n a t u r a l
g a s e s , a n d p e t r o l e u m f r a c t i o n s a r e i n t r o d u c e d a n d t h e n t y p e s
a n d i m p o r t a n c e o f c h a r a c te r i z a t io n a n d p h y s i c al p r o p e r t ie s
a r e d i s c u s s e d . A p p l i c a t i o n o f m a t e r i a l s c o v e r e d i n t h e b o o k i n
v a r i o u s p a r t s o f th e p e t r o l e u m i n d u s t ry o r a c a d e m i a a s w e l l
a s o r g a n i z a t i o n o f t h e b o o k a r e t h e n r e v i e w e d f o l lo w e d b y
s p e c if i c f e a t u r e s o f t h e b o o k a n d i n t r o d u c t i o n o f s o m e o t h e r
r e l a t e d b o o k s . F i n a l l y , u n i t s a n d t h e c o n v e r s i o n f a c t o r s f o r
t h o s e p a r a m e t e r s u s e d i n t h i s b o o k a r e g i v e n a t t h e e n d o f t h e
c h a p t e r .
1 .1 N A T U R E O F P E T R O L E U M F L U I D S
P e t r o l e u m i s o n e o f t h e m o s t i m p o r t a n t s u b s t a n c e s c o n s u m e d
b y m a n a t p r e s e n t t im e . I t is u s e d a s a m a i n s o u r c e o f e n e r g y
f o r in d u s t ry , h e a t i n g , a n d t r a n s p o r t a t i o n a n d i t a l s o p r o -
v i d e s t h e r a w m a t e r i a l s f o r t h e p e t r o c h e m i c a l p l a n t s t o p r o -
d u c e p o l y m e r s , p la s ti c s, a n d m a n y o t h e r p r o d u c t s . T h e w o r d
petroleum, d e r i v e d f r o m t h e L a t i n w o r d s petra a n d oleum,
m e a n s l i te r a l ly rock oil a n d a s p e c i a l t y p e o f o i l c a l l e d o l e u m
[ 1] . P e t r o l e u m i s a c o m p l e x m i x t u r e o f h y d r o c a r b o n s t h a t
o c c u r i n t h e s e d i m e n t a r y r o c k s i n t h e f o r m o f g a s e s ( n a t u r a l
Copyright 9 2005 by AST M International www.astm.org
 
2 C H A R A C T E R I Z A T I O N A N D P R O P E R T I E S O F P E T R O L E U M F R A C T I O N S
g a s ) , l i q u i d s ( c r u d e o i l) , s e m i s o l i d s ( b i t u m e n ) , o r s o l i d s ( w a x
o r a s p h a l t it e ) . L i q u i d f u e l s a r e n o r m a l l y p r o d u c e d f r o m l iq -
u i d h y d r o c a r b o n s , a l t h o u g h c o n v e r s i o n o f n o n l i q u i d h y d r o -
c a r b o n s s u c h a s c o a l , o i l s h a l e , a n d n a t u r a l g a s t o li q u i d f u e l s
i s b e i n g i n v e s ti g a t ed . I n t h i s b o o k , o n l y p e t r o l e u m h y d r o c a r -
b o n s i n th e f o r m o f g a s o r l iq u id , s i m p l y ca l l ed pe t ro l eum f l u -
i d s , a r e c o n s i d e r e d . L i q u i d p e t r o l e u m i s a l s o s i m p l y c a l le d oil .
H y d r o c a r b o n g a s e s i n a r e s e r v o i r a r e c a l l e d a na tura l gas o r
s i m p l y a gas . A n u n d e r g r o u n d r e s e r v o i r t h a t c o n t a i n s h y d r o -
c a r b o n s i s cal led petrole um reservoir a n d i t s h y d r o c a r b o n c o n -
t e n t s t h a t c a n b e r e c o v e r e d t h r o u g h a p r o d u c i n g w e l l i s c a l l e d
reservoir f luid. R e s e r v o i r f lu i d s i n th e r e s e r v o i r s a r e u s u a l l y i n
c o n t a c t w i t h w a t e r i n p o r o u s m e d i a c o n d i t i o n s a n d b e c a u s e
t h e y a r e l i g h t e r t h a n w a t e r, t h e y s t a y a b o v e t h e w a t e r l e v e l
u n d e r n a t u r a l c o n d i t i o n s .
A l t h o u g h p e t r o l e u m h a s b e e n k n o w n f o r m a n y c e n t u r i e s ,
t h e f i r s t o i l - p r o d u c i n g w e l l w a s d i s c o v e r e d i n 1 8 5 9 b y E . L .
D r a k e i n t h e s t a te o f P e n n s y l v a n i a a n d t h a t m a r k e d t h e
b i r t h o f m o d e r n p e t r o l e u m t e c h n o l o g y a n d r e f in i ng . T h e
m a i n e l e m e n t s o f p e t r o l e u m a r e c a r b o n ( C) a n d h y d r o g e n
( H ) a n d s o m e s m a l l q u a n t i t i e s o f s u l f u r (S ) , n i t r o g e n ( N ) ,
a n d o x y g e n ( O) . T h e r e a r e s e v e r a l t h e o r i e s o n t h e f o r m a t i o n
o f p e t r o l e u m . I t i s g e n e r a ll y b e l ie v e d t h a t p e t r o l e u m i s d e -
r i v e d f r o m a q u a t i c p l a n t s a n d a n i m a l s t h r o u g h c o n v e r s i o n o f
o r g a n i c c o m p o u n d s i n t o h y d r o c a r b o n s . T h e s e a n i m a l s a n d
p l a n t s u n d e r a q u a t i c c o n d i t i o n s h a v e c o n v e r t e d i n o r g a n ic
c o m p o u n d s d i s s o l v e d i n w a t e r ( s u c h a s c a r b o n d i o x i d e ) t o
o r g a n i c c o m p o u n d s t h r o u g h t h e e n e r g y p r o v i d e d b y th e s u n .
A n e x a m p l e o f s u c h r e a c t i o n s i s s h o w n b e l o w :
( 1 . 1) 6 C O 2 + 6 H 2 0 d - e n e r g y - -~ 6 0 2 + C6H12 6
i n w h i c h C6H12 6 i s a n o r g a n i c c o m p o u n d c a l l e d c a r b o h y -
d r a t e . I n s o m e c a s e s o r g a n i c c o m p o u n d s e x i st in a n a q u a t i c
e n v i r o n m e n t . F o r e x a m p l e , t h e N i le r i v e r i n E g y p t a n d t h e
U r u g u a y r i v e r c o n t a i n c o n s i d e r a b l e a m o u n t s o f o r g a n i c m a -
t e r ia l s . T h i s m i g h t b e t h e r e a s o n t h a t m o s t o i l r e s e r v o ir s a r e
l o c a te d n e a r t h e s e a . T h e o r g a n ic c o m p o u n d s f o r m e d m a y b e
d e c o m p o s e d i n t o h y d r o c a r b o n s u n d e r c e r t a i n c o n d i t i o n s .
(1 .2) (CHEO)n - -~ xCO2 d-yC H4
i n w h i c h n , x, y , a n d z a r e i n t e g e r n u m b e r s a n d y C H z i s t h e
c l os e d f o r m u l a f o r th e p r o d u c e d h y d r o c a r b o n c o m p o u n d .
A n o t h e r t h e o r y s u g g e s t s t h a t t h e i n o r g a n i c c o m p o u n d c a l -
c i u m c a r b o n a t e ( C a C O 3) w i t h a l ka l i m e t a l c a n b e c o n v e r t e d t o
c a l c i u m c a r b i d e ( Ca C2 ), a n d t h e n c a l c i u m c a r b i d e w i t h w a t e r
( H 2 0 ) c a n b e c o n v e r t e d t o a c e t y l e n e ( C 2H 2 ). F i n a ll y , a c e t y l e n e
c a n b e c o n v e r t e d t o p e t r o l e u m [ 1 ]. C o n v e r s i o n o f o r g a n i c m a t -
t e r s i n t o p e t r o l e u m i s ca l l ed m a t u r a t i o n . T h e m o s t i m p o r t a n t
f a c t o r s in t h e c o n v e r s i o n o f o r g a n i c c o m p o u n d s t o p e t r o l e u m
h y d r o c a r b o n s a r e ( 1 ) h e a t a n d p r e s s u r e , ( 2) r a d i o a c t i v e ra y s ,
s u c h a s g a m m a r a y s , a n d ( 3 ) c a t a l y ti c r e a c ti o n s . V a n a d i u m -
a n d n i c k e l - t y p e c a t a l y s t s a r e t h e m o s t e f f e c t i v e c a t a l y s t s i n
t h e f o r m a t i o n o f p e t ro l e u m . F o r t h i s r e a s o n s o m e o f t h e s e
m e t a l s m a y b e f o u n d i n s m a l l q u a n t i t ie s i n p e t r o l e u m f lu i ds .
T h e r o l e o f r a d i o a c t i v e m a t e r i a l s i n t h e f o r m a t i o n o f h y d r o -
c a r b o n s c a n b e b e s t o b s e r v e d t h r o u g h r a d i o a c ti v e b o m b a r d -
i n g o f f a tt y a c id s ( R C O O H ) t h a t f o r m p a r a f f i n h y d r o c a r b o n s .
O c c a s i o n a l l y t r a c e s o f r a d i o a c t i v e m a t e r i a l s s u c h a s u r a n i u m
a n d p o t a s s i u m c a n a l s o b e f o u n d i n p e t r o l e u m . I n s u m m a r y ,
t h e f o l l o w in g s t e p s a r e r e q u i r e d f o r th e f o r m a t i o n o f h y d r o c a r -
b o n s : ( 1 ) a s o u r c e o f o r g a n i c m a t e r i a l , ( 2 ) a p r o c e s s t o c o n v e r t
o r g a n i c c o m p o u n d s i n t o p e t r o l e u m , a n d ( 3 ) a s e a l e d r e s e r v o i r
s p a c e t o s t o re t h e h y d r o c a r b o n s p r o d u c e d . T h e c o n d i t i o n s r e -
q u i r e d f o r t h e p r o c e s s o f c o n v e r s i o n o f o r g a n ic c o m p o u n d s
i n t o p e t r o l e u m ( a s s h o w n t h r o u g h E q . ( 1 . 2 ) a r e ( 1 ) g e o l o g i c
t i m e o f a b o u t 1 m i l l i o n y e a r s , (2 ) m a x i m u m p r e s s u r e o f
a b o u t 1 7 M P a ( 2 5 0 0 p s i ) , a n d ( 3 ) t e m p e r a t u r e n o t e x c e e d -
i n g 1 0 0 -1 2 0 ~ ( ~ 2 1 0 - 2 50 ~ I f a l e a k o c c u r r e d s o m e t i m e
i n t h e p a s t , th e e x p l o r a t i o n w e l l w i l l e n c o u n t e r o n l y s m a l l
a m o u n t s o f r e s i d u a l h y d r o c a r b o n s . I n s o m e c a s e s b a c t e r i a
m a y h a v e b i o d e g r a d e d t h e o il , d e s tr o y i n g l ig h t h y d r o c a r b o n s .
A n e x a m p l e o f s u c h a c a s e w o u l d b e t h e l a r g e h e a v y o il a c c u -
m u l a t i o n s i n V e n e z u e l a . T h e h y d r o c a r b o n s g e n e r a t e d g r a d -
u a l l y m i g r a t e f r o m t h e o r i g i n a l b e d s t o m o r e p o r o u s r o c k s ,
reservoir.
o f r e s e r v o i r s w i t h i n a c o m m o n r o c k i s c a l le d a n oil field.
P e t r o l e u m i s a m i x t u r e o f h u n d r e d s o f d if f e r e n t id e n t if i a b le
h y d r o c a r b o n s , w h i c h a r e d i s c u s s e d i n t h e n e x t s e c ti o n . O n c e
p e t r o l e u m i s a c c u m u l a t e d i n a r e s e r v o i r o r i n v a r i o u s s e d i -
m e n t s , h y d r o c a r b o n c o m p o u n d s m a y b e c o n v e rt e d fr o m o n e
f o r m t o a n o t h e r w i t h t i m e a n d v a r y i n g g e o l o g ic a l c o n d it i o n s .
T h i s p r o c e s s i s c a l le d in-s i tu a l terat ion, a n d e x a m p l e s o f c h e m -
i c a l a l t e r a t i o n a r e t h e r m a l m a t u r a t i o n a n d m i c r o b i a l d e g r a -
d a t i o n o f th e r e s e r v o i r o il . E x a m p l e s o f p h y s i c a l a l t e r a t i o n o f
p e t r o l e u m a r e t h e p r e f e r e n t i a l l o s s o f lo w - b o i li n g c o n s t i t u e n t s
b y t h e d i f f u s i on o r a d d i t i o n o f n e w m a t e r i a l s t o t h e o il i n
p l a c e f r o m a s o u r c e o u t s i d e t h e r e s e r v o i r [1 ]. T h e m a i n d i f -
f e r e n c e b e t w e e n v a r i o u s o i l s f r o m d i f f e re n t f ie l ds a r o u n d t h e
w o r l d i s t h e d i ff e r e n c e i n t h e ir c o m p o s i t i o n o f h y d r o c a r b o n
c o m p o u n d s . T w o o i ls w i t h e x a c t ly t h e s a m e c o m p o s i t i o n h a v e
i d e n t ic a l p h y s i c a l p r o p e r t i e s u n d e r t h e s a m e c o n d i t i o n s [ 2 ].
A g o o d r e v ie w o f s t a ti s t ic a l d a t a o n t h e a m o u n t o f oi l a n d
g a s r e s e r v o i r s , t h e i r p r o d u c t i o n , p r o c e s s i n g , a n d c o n s u m p -
t i o n i s u s u a l l y r e p o r t e d y e a r l y b y t h e O i l a n d G a s J o u r n a l
( O G J ). A n a n n u a l r e f i n e ry s u r v e y b y O G J i s u s u a l ly p u b l i s h e d
i n D e c e m b e r o f e a c h y e ar . O G J a l s o p u b l is h e s a f o r e c a s t a n d
r e v i e w r e p o r t i n J a n u a r y a n d a m i d y e a r f o r e c a s t r e p o r t i n
J u l y o f e a c h y e a r . I n 2 0 0 0 i t w a s r e p o r t e d t h a t t o t a l p r o v e n o il
r e s e r v e s i s e s t i m a t e d a t 1 0 1 6 b i l l i o n b b l ( 1 . 0 1 6 x 1 0 t z b b l ) ,
w h i c h f o r a t y p i c a l oi l i s e q u i v a l e n t t o a p p r o x i m a t e l y 1 .3 9 x
1011 t o n s . T h e r a t e o f o il p r o d u c t i o n w a s a b o u t 6 4 . 6 m i l l i o n
b b l / d ( ~ 3 . 2 3 b i l l io n t o n / y e a r ) t h r o u g h m o r e t h a n 9 0 0 0 0 0 p r o -
d u c i n g w e l l s a n d s o m e 7 5 0 r e f in e r i e s [ 3 , 4 ] . T h e s e n u m b e r s
v a r y f r o m o n e s o u r c e t o a n o t h e r. F o r e x a m p l e , E n e r g y I n f o r -
m a t i o n A d m i n i s t ra t i o n o f U S D e p a r t m e n t o f E n e rg y r e p o r t s
w o r l d o i l r e s e r v e s a s o f J a n u a r y 1 , 2 0 0 3 a s 1 2 1 3. 1 12 b i l l i o n
b b l a c c o r d i n g t o O G J a n d 1 0 3 4 . 6 7 3 b i l l i o n b b l a c c o r d i n g t o
Wor ld O i l ( w w w . e i a . d o e . g o v / e m e u / i e a ) . A c c o r d i n g t o t h e O G J
w o r l d w i d e p r o d u c t i o n r e p o r t s Oi l and Gas Journa l , Dec. 22 ,
2 0 0 3 , p . 4 4) , w o r l d o i l r e s e r v e s e s t i m a t e s c h a n g e d f r o m 9 9 9 . 7
i n 1 9 9 5 t o 1 2 6 5 .8 1 1 b i l l i o n b b l o n J a n u a r y 1 , 2 0 0 4 . F o r t h e
s a m e p e r i o d w o r l d g a s r e s e r v e s e s t im a t e s c h a n g e d f r o m 4 . 9 8 x
1 01 5 s c f t o 6 .0 6 8 3 x 1 0 15 s c f . I n 2 0 0 3 o i l c o n s u m p t i o n w a s
a b o u t 7 5 b i l l i o n b b l / d a y , a n d i t i s e x p e c t e d t h a t i t w i l l i n -
c r e a s e t o m o r e t h a n 1 10 m i l l i o n b b l / d a y b y t h e y e a r 2 02 0 .
T h i s m e a n s t h a t w i t h e x i st i ng p r o d u c t i o n r a t e s a n d r e s e r v e s ,
i t w i ll t a k e n e a r l y 4 0 y e a r s f o r t h e w o r l d s o i l t o e n d . O i l
r e s e r v e s l i fe ( r e s e r v e s - t o - p r o d u c t i o n r a t io ) i n s o m e s e l e c t e d
c o u n t r i e s i s g i v e n b y O G J ( D e c . 2 2 , 20 0 4 , p . 4 5) . A c c o r d i n g
 
1. I N T R O D U C T I O N 3
in Iraq. As in January l, 2002, the total number of world oil
wells was 830 689, excluding shut or service wells (OGJ, Dec.
22, 2004). Estimates of world oil reserves in 1967 were at
418 billion and in 1987 were at 896 billion bbl, which shows
an increase of 114 in this period [5]. Two-thirds of these
reserves are in the Middle East, although this portion de-
pends on the type of oil considered. Although some people
believe the Middle East has a little more than half of world
oil reserves, it is believed that many undiscovered oil reser-
voirs exist offshore under the sea, and with increase in use
of the other sources of energy, such as natural gas or coal,
and through energy conservation, oil production may well
continue to the end of the century. January 2000, the total
amo unt of gas reserves was about 5.15 • 1015 scf, and
its pr odu ct ion in 1999 was abo ut 200 x 109 scf/d (5.66 x
109 sm3/d) through some 1500 gas plants [3]. In January
2004, according to OGJ (Dec. 22, 2004, p. 44), world natu-
ral gas res erves stood at 6.068 • 1015 scf (6068.302 trillion
scf). This shows that existing gas reserves may last for some
70 years. Estimated natural gas reserves in 1975 were at
2.5 x 1015 scf (7.08 x 1013 sm3), that is, abou t 50 of cu rrent
reserves [6]. In the United States, cons umpt ion of oil and gas
in 1998 was abou t 65 of total energy cons umpti on. Crude
oil demand in the United State in 1998 was about 15 million
bbl/d, that is, abou t 23 of total world crude produc tion [3].
Worldwide consumption of natural gas as a clean fuel is on
the rise, and attempts are underway to expand the trans-
fer of natural gas through pipelines as well as its conver-
sion to liquid fuels such as gasoline. The world energy con-
sump tion is distribute d as 35 thro ugh oil, 31 thro ugh
coal, and 23 thro ugh natura l gas. Nearly 11 of total
world energy is produced through nuc lear and hydroelectric
sour ces [ 1].
In early days of chemistry science, chemical compoun ds were
divided into two groups: inorganic and organic, depending
on their original source. Inorganic comp ounds were obtained
from minerals, while organic compound s were obtained from
living organisms and contained carbon. However, now or-
ganic compounds can be produced in the laboratory. Those
organic compou nds that contain only elements of carbon (C)
and hydrogen (H) are called hydrocarbons and they form
the largest group of organic compounds. There might be as
many as several thousand different hydroca rbon compound s
in petroleum reservoir fluids. Hydr ocarbon com pounds have
a general closed fo rmula of CxHy, where x a nd y are integer
numbers. The lightest hydrocarbon is methane (CH4), which
is the main component in a natural gas. Methane is from a
group of hydroca rbons called paraffins. Generally, hydrocar-
bons are divided into four groups: (1) paraffins, (2) olefins,
(3) naphthenes, and (4) aromatics. Paraffins, olefins, and
naphthenes are sometime called aliphatic versus aromatic
compounds. The International Union of Pure and Applied
Chemistry (IUPAC) is a nongovernment organization that
provides standard names, nomenclature, and symbols for dif-
ferent chemical compounds that are widely used [7]. The
relationship between the various hydrocarbon constituents
of crude oils is hydrogen addition or hydrogen loss. Such
interconversion schemes may occur during the formation,
maturation, and in-situ alteration of petroleum.
Paraffins are also called alkanes and have the general for-
mula of C, Han+a, where n is the num ber of carb on a toms.
Paraffins are divided into two groups o f norm al and isoparaf-
fins. Normal paraffins or normal alkanes are simply written
as n-paraffins or n-alkanes and they are open, straight-chain
saturated hydrocarbons. Paraffins are the largest series of hy-
droc arbo ns and be gin with meth ane (CH4), which is also rep-
resented by C1. Three n-alkanes, me than e (C1), ethan e (C2),
and n- butane (C4), are sh own below:
H H H H H H H
H - - C - - H H - - C - - C - - H H - - C - - C - - C - - C - - H
H H H H H H H
M e t h a n e E t h a n e n - B u t a n e
CH4) C2H6) C4H1~
The open formul a for n-C4 can also be show n as CH3--
CH2--CH2--CH3 and for simplici ty in drawing, us ually the
CH3 and CH2 groups are not written and only the carbon-
carbon bonds are drawn. For example, for a n-alkane com-
pound of n-heptadecane with the formula of C 1 7 H 3 6 , the
structure can also be shown as follows:
n-Heptadecane C17H36)
are branched-type hydrocarbons and begin with isobutane
(methylpropane), which has the same closed formula as n-
butane (Call10). Compounds of different structures but the
same closed formula are called isomers. Three branched or
isoparaffin compoun ds are shown below:
CH3 CH3 CH3
isobutane i sopen~anemethylbutane) isooc tane 2-methylheptane)
C4HIo) C5H12) C8HI8)
In the case of isooctane, if the methyl group (CH3) is at-
tached to another carbon, then we have another compound
(i.e., 3-methylheptane). It is also possible to have more than
one branch of CH3 group, for example, 2,3-dimethylhexane
and 2-methylheptane, which are simply shown as following:
2 - M e t h y l h e p t a n e C s H l s )
2 , 3 - D i m e t h y l h e x a n e C 8 H 1 8 )
Numbers refer to carbon numbers where the methyl group
 
Number of CarbonAtoms
FIG 1 1reNu mb er of possib le a lkane isomers
4 C H A R A C T E R I Z A T I O N A N D P R O P E R T I E S O F P E T R O L E U M F R A C T I O N S
50
from the right or from the left. There are 2 isomers for bu-
tane and 3 for pentane, but there are 5 isomers for hexane, 9
for heptane, 18 for octane (C8H18), and 35 for nonane. Sim-
ilarly, dodecane (C12H26) has 355, while octadecane (C18H38)
has 60523 and C40 has 62 x 1012 isomers [1, 8, 9]. The num-
ber of isomers rapidly increases with the nu mber of carbon
atoms in a molecule because of the rapidly rising number of
their possible structural arrangements as shown in Fig. 1.1.
For the paraffins in the range of Cs-C12, the number of iso-
mers is more than 600 although only about 200-400 of them
have been identified in petro leum mixtures [ 10]. Isomers have
different physical properties. The same increase in num ber
of isomers with molecular weight applies to other hydro-
carbon series. As an example, the total number of hydrocar-
bons (from different groups) having 20 carbon atoms is more
than 300000 [10]
Under standa rd condit ions (SC) of 20~ and 1 atm, the
first four members of the alkane series (methane, ethane,
propane, and butane) are in gaseous form, while from C5Hl1
(pentane) to n-hexadecane
n-heptadecane (C17H38) the com pou nds exist as waxlike solids
at this standard temperature and pressure. Paraffins from C1
to C40 usually app ear in crude oil and represe nt up to 20% of
crude by volume. Since paraffins are fully satura ted (no dou-
ble bond), they are stable and remain unchanged over long
periods of geological time.
they are unsaturated and have at least one double bond
between carbon-carbon atoms. Compounds with one dou-
ble bond are called monoolefins or alkenes, such as ethene
(also named ethylene: CH2=CH2) and propene or propylene
(CH2=CH--CH3). Besides s tructural isomerism connected
with the location of double bond, there is another type of iso-
merism called geometric isomerism which indicates the way
atoms are oriented in space. The configurations are differen-
tiated in their names by the prefixes
cis-
and
trans-
cis- and t rans-2-butene. Monoolefins have a general formula
of CnH2n. If there are two double bonds, the olefin is called
diolefin (or diene), such as butadiene (CH2=CH--CH=CH2).
Unsaturated c ompound s are more reactive than saturated hy-
drocarbons (without double bond). Olefins are unc omm on in
crude oils due to their reactivity with hydrogen that makes
them saturated; however, they can be produced in refiner-
ies through cracking reactions. Olefins are valuable prod-
ucts of refineries and are used as the feed for petrochemical
plants to produce polymers such as polyethylene. Similarly
compounds with trip le b ond s s uch as acetyle ne (CH -----CH)are
not found in crude oils because of their tendency to become
saturated [2].
Nap hth en es or cycloalkanes are ring or cyclic saturated hy-
droca rbons with the general form ula of CnH2n. Cyclopent ane
(C5H10), cyclohexane (C6H12), and their derivatives such as
n-alkylcyclopentane s are normal ly found in crude oils. Three
types of naphthenic compou nds are shown below:
Cyclopentane Methylcyclopentane Ethylcyclohexane
CsHIo) C6HI2) C8H~6)
If there is on ly one alkyl group from n-paraffins (i.e., methyl,
ethyl, propyl, n-butyl ... ) attached to a cyclopentane hydro-
carbon, the series is called n-alkylcyclopentanes such as the
two hydrocarbons shown above where on each junction of the
ring there is a CH2 group except on the alkyl group juncture
where there is only a CH group. For simplicity in drawing,
these groups are not shown. Similarly there is a homologous
napthenic series of
above. Napthenic hydrocarbons with only one ring are also
called
monocycloparaffins
or
cloparaff ins orpolyn aphthen es may also be available. Thermo-
dynamic studies show that naphthene rings with five and six
carbon atoms are the most stable naphthenic hydrocarbons.
The content of cycloparaffins in petroleum may vary up to
60%. Generally, any petroleum mixture that has hydrocarbon
compou nds with five carbon atoms also contains naphthenic
compounds.
A r o m a t i c s are an import ant series of hydrocarb ons found
in almost every petroleum mixture from any part of the world.
Aromatics are cyclic but uns aturated hydrocarb ons that begin
with benzene molecule
and contain carbon-carbon
double bonds. The name aromati c refers to the fact that such
hydrocarbo ns common ly have fragrant odors. Four different
aromatic com pound s are shown below:
9
Benzene Toluene O-xylene Naphthalene
In the above structures, on each junction on the benzene
ring where there a re three bonds, there is only a group of CH,
while at the junction with an alkylgroup (i.e., toluene) there
is only a C atom. Although benzene has three carb on-c arbon
double bonds, it has a unique ar rangement of electrons that
allows benzene to be relatively unreactive. Benzene is, how-
ever, known to be a cancer-inducing compound [2]. For this
reason, the amount of benzene allowed in petroleum prod-
ucts such as gasoline or fuel oil is limited by government
regulations in many countries. Under SC, benzene, toluene,
and xylene are in liquid form while naphthalene is in a solid
state. Some of the common aromatics found in petroleum
and crude oils are benzene and its derivatives with attached
methyl, ethyl, propyl, or higher alkyl groups. This series of
aromatics is called alkylbenzenes and compounds in this ho-
mologous group of hydrocarbons have a general formula
of CnH2n-6 (where n _> 6). Generally, aro mat ic series with
only one benzene ring are also called monoaromat ics (MA)
or monon uclear aromatics. Naphthalene and its derivatives,
which have only two unsaturate d rings, are sometime called
diaromatics. Crude oils and reservoir fluids all contain aro-
matic c ompounds. However, heavy petroleum fractions and
residues contain multi-unsaturated rings with many benzene
and napht hene rings attached to each other. Such aromatics
(which unde r SC are in solid form) are also cal ledpolyaromat
ics (PA) or polynu clear aroma tics (PNA). In this boo k terms o f
mono and polyaromatics are used. Usually, heavy crude oils
contain more aromatics th an do light crudes. The amount of
aromatics in coal liquids is usually high and could reach as
high as 98 by volume. It is com mon to have compou nds
with napthenic and aromatic rings side by side, especially
in heavy fractions. Monoaromatics with one napthenic ring
have the formula of CnH2n-8 and with two n apht henic rings
the fo rmula is C~Hzn-8. There are man y comb inati ons of alkyl-
naph then oaro mati cs [ 1, 7].
Normally, high-molecular-weight polyaromatics contain
several heteroatoms such as sul fur (S), nitro gen (N), or oxygen
(O) hut the comp ound is still called an aromatic hydrocarbon.
Two types of these com pou nds are s hown be low [1 ]:
H
enzocarbazo le CI6H1 N)
Except for the atoms S an d N, which are specified in the above
structures, on other junctions on each ring there is either a
CH group or a carbon atom. Such heteroatoms in multiring
aromatics are commo nly found in asphaltene c ompound s as
shown in Fig. 1.2, where for simplicity, C and H a toms a re not
shown on the rings.
Sulfur is the most importan t hetero atom in petroleum and
it can be found in cyclic as well as noncyclic compou nds such
as mercaptanes (R--S--H) and sulfides (R--S--W), where R
and R' are alkyl groups. Sulf ur in natural gas is usually found
in the form of hydrogen sulfide (H2S). Some natural gases
C : 8 3 . 1
H/C: i.28
M o l e c u l ar W e i g h h 1 3 7 0
1. I N T R O D U C T I O N 5
F I G . 1 . 2 m A n e x a m p l e o f a s p h a l t e n e m o l e c u l e . R e p r i n t e d f r o m
Ref . [1 ] p . 463 by cou r tesy o f Marce l Dekker Inc .
conta in HzS as high as 30 by volume. The amo unt of sulfur
in a crude ma y vary from 0.05 to 6 by weight. In Chapte r 3,
further discussion on the sulfur contents of petroleum frac-
tions an d crude oils will be presented. The prese nce of sulfur
in finished petroleum products is harmful, for example, the
presence of sulfur in gasoline can pro mote corrosion of en-
gine parts. Amounts of nitrogen and oxygen in crude oils are
usually less than the am ount of sulfur by weight. In general
for petroleum oils, it appears that the compositions of ele-
ments v ary within fairly narr ow limits; on a weight basis they
are [1]
Nitrogen (N), 0.1-2.0
Oxygen (O), 0.05-1.5
Sulfur (S), 0.05-6.0
Metals (Nickel, Vanad ium, an d Copper), < 1000 pp m (0.1 )
Generally, in heavier oils (lower API gravity, defined by
Eq. (2.4)) prop orti ons of carbon, sulfur, nitrogen, and oxygen
elements increase but the amou nt of hydrogen and the overall
quality decrease. Further information and discussion about
the chemistry of petroleum and the type of compou nds found
in petro leum fractions are given by Speight [ 1]. Physical prop-
erties of some selected pure hy drocarbons f rom different ho-
mologous groups commonly found in petroleum fluids are
given in Chapter 2. Vanadium concentrations of above 2 ppm
in fuel oils can lead to severe corros ion in turbine blades an d
deteriora tion of refrac tory in furnaces. Ni, Va, and Cu can also
severely affect the activities of catalysts and result in lower
products. The metallic content may be reduced by solvent
extraction with organic solvents. Organometallic compo unds
are precipitated with the asphaltenes and residues.
1 1 2 R e s e r v o i r F l u i d s a n d C r u d e O i l
The word f lu id refers to a pure substance or a mixture of com-
pounds that are in the form of gas, liquid, or both a mixture
of liquid and gas (vapor). Reservoir fluid is a term used for the
mixture of hydrocarbons in the reservoir or the stream leaving
a produ cing well. Three fac tors determi ne if a reservoir fluid is
in the for m of gas, liquid, or a mixture of gas and liquid. These
factors are (1) comp osit ion of reservoir fluid, (2) temperature,
and (3) pressure. The most impo rtant characteri stic of a reser-
voir fluid in addition to specific gravity (or API gravity) is its
gas-to-oil ratio (GOR), which represents the amount of gas
 
6 C H A R A C T E R I Z A T I O N A N D P R O P E R T I E S O F P E T R O L E U M F R A C T I O N S
TABLE 1.1--Types and c haracteristics of various reservoir fluids.
Reservoir fluid ype GOR, scf/sth CH4, mol% C6+, tool% API gravityof STOa
Black oil <1000 _<50 >_30 <40
Volatile oil 1000-3000 50-70 10-30 40-45
Gas condensate 3000-50 000 70-85 3-10 _>45
Wet gas _>50 000 >-75 <3 >50
Dry gas >-10 0000 >_90 < 1 No liq uid
API gravityof stock tank oil (STO) produced at the surface facilitiesat standard conditions(289 K and 1 atm).
produced at SC in standard cubic feet (scf) to the amount of
liquid oil produ ced at the SC in stock tank barrel (stb). Other
unit s of GOR are discussed in Section 1.7.23 and its calcula-
tion is discusse d in C hapter 9. Generally, reservoir fluids are
categorized into four or five types (their characteristics are
given in Table 1.1). These five fluids in the direction of in-
creasing GOR are bl ack oil, volatile oil, gas conde nsate, wet
gas, and dry gas.
If a gas after surface separator, under SC, does not pro-
duce any liquid oil, it is called
dry gas .
A natu ral gas that after
prod ucti on at the surface facilities can pro duce a little liquid
oil is called w e t g a s . The word wet does not mean that the
gas is wet with water, but refers to the hydrocarbon liquids
that condense at surface condit ions. In dry gases no l iquid
hydrocarbon is formed at the surface conditions. However,
both dry and wet gases are in the category of natural gases.
Volatile oils have also bee n called h i g h - s h r i n k a g e c r u d e o i l and
near-cr i t ica l o i l s , since the reservoir temperature and pressure
are very close to the critical point of such oils, but the critical
temperatur e is always greater than the reservoir temperature
[i 1]. Gases and gas conde nsate fluids have critical temper a-
tures less than the reservoir temperature. Black oils contain
heavier compounds and therefore the API gravity of stock
tank oil is generally lower than 40 and the GOR is less than
1000 scf/stb. The speci ficatio ns given in Table 1.1 for vario us
reservoir fluids, especially at the boun dari es betw een differ-
ent types, are arbitrary and vary from one source to a nother
[9, 11]. It is possible to have a reservoir fluid type that has
propert ies outside the corresponding l imits mention ed ear-
lier. Dete rmin atio n of a type of reservoir fluid by the abov e
rule of thumb based on the GOR, API gravity of stock tank
oil, or its color is not possible for all fluids. A more accu-
rate m etho d of de term inin g the type of a reservoir fluid is
based on the phase behavior calculations, its critical point,
and shape of the phase diagram which will be discussed in
Chapters 5 and 9. In general, oils produced from wet gas,
gas condensate, volatile oil, and black oil increase in spe-
cific gravity (decrease in API gravity and quality) in the same
order. H ere q uality of oil indicates lower carbon , sulfur, nitro-
gen, and metal contents which corr espond to higher heating
value. Liquids from blac k oils are viscous and blac k in color,
while the liquids from gas con densat es or wet gases are clear
and colorless. Volatile oils produce fluids brown with some
red/green color liquid. Wet gas contains less methane than a
dry gas does, bu t a larger fra ction of C2 C 6 components. Ob-
viously the ma in difference bet ween these reservoir fluids is
their respective composition. An example of composition of
diffe rent rese rvoir fluids is given in Table 1.2.
In Table 1.2, C7+ refers to all hydrocarbons having seven
or higher ca rbon atoms and is called heptane-plus fract ion,
while C6 refers to a group of all hydrocarbons with six car-
bon atoms (hexanes) that exist in the fluid.
MT+
an d SG7+ are
the molecula r weight and specific gravity at 15.5~ (60~ for
the C7+ fraction of the mixture, respectively. It should be re-
alized that molec ular weight an d specific gravity of the whole
reservoir fluid are less than the corr espon ding values for the
TABLE 1.2---Composit ion (mol ) and properties of various reservoir luids a nd a crude oil
Component Dry gas~ Wet gasb Gas condensateC Volatileoild Bla ck ile Crude il
CO2 3.70 0.00 0.18 1.19 0.09 0.00
N2 0.30 0.00 0.13 0.51 2.09 0.00
H2S 0.00 0.00 0.00 0.00 1.89 0.00
C1 96.00 82.28 61.92 45.21 29.18 0.00
C2 0.00 9.52 14.08 7.09 13.60 0.19
C3 0.00 4.64 8.35 4.61 9.20 1.88
iC4 0.00 0.64 0.97 1.69 0.95 0.62
nC4 0.00 0.96 3.41 2.81 4.30 3.92
iC5 0.00 0.35 0.84 1.55 1.38 2.11
nC5 0.00 0.29 1.48 2.01 2.60 4.46
C6 0.00 0.29 1.79 4.42 4.32 8.59
C7+ 0.00 1.01 6.85 28.91 30.40 78.23
Total 100.00 100.00 100.00 100.00 100.00 100.00
GOR (scf/stb) .. . 69917 4428 1011 855
M7+ .. . 113 143 190 209.8 266
SG7+ (at 15.5~ .. . 0.794 0.795 0.8142 0.844 0.895
API7+ 46.7 46.5 42.1 36.1 26.6
Gas sample from Salt Lake, Utah [12].
bWet gas data from McCaln [11].
CGas condensate sample from Samson County, Texas (M. B. Standing, personal notes, Department of Petroleum
Engineering,Norwegian nstitute of Technology,Trondheim,Norway, 1974).
dVolatile oil sample from Raleigh Field, Smith County,Mississipi M. B. Standing,personal notes, Department of
Petroleum Engineering,Norwegian nstitute of Technology,Trondheim,Norway, 1974).
eBlack oil sample from M. Ghuraiba, M.Sc. Thesis, Kuwait University,Kuwait, 2000.
fA crude oil sample produced at stock tank conditions.
 
1. I N T R O D U C T I O N 7
heptane-plus fraction. For example, for the crude oil sample
in Table 1.2, the specific gravity of the whole c rude oil is 0.871
or API gravity of 31. Details of suc h calculat ions are discussed
in Chapter 4. These compositions have been de termined from
recombination of the compositions of corresponding sepa-
rator gas and stock tank liquid, which have been measured
thro ugh analytic al tools (i.e., gas chroma tograp hy, mass spec-
trometry, etc.). Composi tion of reservoir fluids varies with the
reservoir pressure and reservoir depth. Generally in a produc -
ing oil field, the sulfur and amount of heavy compounds in-
crease versus production time [10]. However, it is important
to note that within an oil field, the concentration of light hy-
droc arbo ns and the API gravity of the reservoir fluid increase
with the reservoir depth, while its sulfur and C7 contents de-
crease with the depth [ 1 . The lumped C7+ fraction in fact is
a mixture of a very large number of hydrocarbons, up to C40
or higher. As an example the number of pure hydrocarbons
from C5 to C9 detected b y chro mat ogr aph y tools in a crude oil
from North Sea reservoir fluids was 70 compounds. Detailed
composition of various reservoir fluids from the North Sea
fields is provided by Pe dersen et al. [13]. As shown in Chapter
9, using the knowledg e of the compo siti on of a reservoir fluid,
one can determine a pressure-temperature (PT) diagram of
the fluid. And on the basis of the temperature and pressure
of the reservoir, the exact type of the reservoir fluid can be
determined from the P T diagram.
Reservoir fluids from a producing well are conducted to
temperature of the stream to atmospheric pressure and tem-
perature. The liquid leaving the last stage is called s t o c k t a n k
oi l (STO) and the gas released in various stages is called as
sociated gas . The liquid oil after nece ssary field process ing is
called crude o i l . The main factor in operation and design of an
oil-gas separator is to find the opt imum operating conditions
of temperature and pressure so that the amou nt of produced
liquid (oil) is maximized. Suc h conditions ca n be determine d
through phase behavior calculations, which are discussed in
detail in Chapte r 9. Reservoir fluids from produc ing wells are
mixed with free water. The water is separated through gravi-
tational separators based on the difference between densities
of water and oil. Remaining water from the crude can be re-
moved through dehydration processes. Another surface oper-
ation is the desalting process that is necessary to remove the
salt content of crude oils. Separation of oil, gas, and water
from each other and removal of water and salt from oil and
any other process that occurs at the surface are called sur face
produc t ion opera t ions [14].
The crude oil produced from the atmospheric sepa rator has
a composition different from the reservoir fluid from a pro-
ducing well. The light gases are separated and usually crude
oils have almost no met hane and a small C2-C3 content while
the C7+ conte nt is highe r than the original res ervoir fluid. As
an example, the compos ition of a crude oil produced throug h
a three-stage separator from a reservoir fluid is also given in
Table 1.2. Actually this crude is produced from a black oil
reservoir fluid (composition given in Table 1.2). Two impor-
tant characterisitcs of a crude that determine its quality are
the API gravity (specific gravity) and the sulfur conte nt. Gen-
erally, a crud e with the API gravit y of less than 20 (SG > 0.934)
is called heavy c rude and with API gravity of greater than 40
(SG < 0.825) is called l i gh t c rude [1, 9]. Similarly, if the sulfur
cont ent of a crude is less tha n 0.5 wt it is called a sweet
oil. It should be realized that these ranges for the gravity and
sulfur content are relative and may vary from one source to
another. Fo r example, Fav ennec [15] classifies heavy crude as
those with API less than 22 and light crude having API above
33. Further classification of crude oils will be discussed in
Chapter 4.
1 1 3 P e t r o l e u m F r a c t io n s a n d P r o d u c t s
A crude oil produced after necessary field processing and
surface operations is transferred to a refinery where it is
processed and converted into various useful products. The
refining process has evolved from simple batch distillation
in the late nineteenth century to today's complex processes
through modern refineries. Refining processes can be gener-
ally divided into three major types: (1) separation, (2) con-
version, and (3) finishing. Separation is a physical process
where comp ounds are separated by different techniques. The
most important separa t i on process is distillation that occurs
in a distillation column; com pounds are separated based on
the difference in their boiling points. Other major physical
separation processes are absorption, stripping, and extrac-
tion. In a gas plant of a refinery that produces light gases,
the heavy hydrocar bons (Cs and heavier) in the gas mixture
are separated through their absorption by a liquid oil sol-
vent. The solvent is then regenerated in a stripping unit. The
conver s ion process consists of chemical changes that occur
with hydroca rbons in reactors. The purpose of such reactions
is to convert hydrocarbon compounds from one type to an-
other. The most important reaction in modem refineries is
the cracking in which heavy hydrocarbons are converted to
lighter and more valuable hydrocarbons. Catalytic cracking
and thermal cracking are co mmonl y used for this purpose.
Other types of reactions such as isomerization or a lky la t i on
are used to produce high octane numbe r gasoline. F i n i s h i n g is
the purification of various product streams by processes such
as desulfurization or acid treatment of petroleum fractions to
remove impurities from the product or to stabilize it.
After the desalting process in a refinery, the crude oil en-
ters the atmospheric distillation column, where compounds
are separated according to their boiling points. Hy drocarbon s
in a crude have boiling points ranging from -160~ (boil-
ing point of methane) to more than 600~ (ll00~ which
is the boiling point of heavy compounds in the crude oil.
However, the carbon-carbon bond in hydrocarbons breaks
down at temper atures aroun d 350~ (660~ This process is
called crack ing and it is undesirable during the distillation
process since it changes the structure of hydrocarbons. For
this reason, compounds having boiling points above 350~
(660+~ called residuum are removed from the bottom of
atmospheric distillation column and sent to a vacuum dis-
tillation column. The pressure in a vacuum distillation col-
umn is about 50-100 mm Hg, where hydrocarbons are boiled
at much lower temperatures. Since distillation cannot com-
pletely separate the compounds, there is no pure hyd rocarb on
as a produc t of a distillation column. A group of hydrocarbons
can be separated through distillation according to the boiling
point of the lightest and heaviest com pounds in the mixtures,
The lightest product of an atmospheri c colu mn is a mixture of
 
TABLE 1.3---Somepetroleum fractions produced from distillation columns
Approximate boiling range
Light gases C 2 - C 4 -90 to 1 -130-30
Gasoline (light and heavy) C 4 - C 1 0 - 1 - 2 0 0 30-390
Naphthas (light and heavy) C 4 - C l l - 1 - 2 0 5 30-400
Jet fuel C 9 - C 1 4 150-255 300-490
Kerosene C11-C14 205-255 400-490
Wax Cls-Ca6 315-500 600-930
Vacuum gas oil C28-C55 425-600 800-1100
Residuum > C55 > 600 > 1100
I n f o r m a t i o n g i v e n i n t h i s t a b l e i s o b t a i n e d f r o m d i f f e r e n t s o u r c e s [ 1 1 8 1 9 ] .
range of -180 to -80~ (-260 to -40~ which corresponds
to the boiling point of methane and ethane. This mixture,
which is in the form of gas and is known as fuel gas, is actu-
ally a
petroleum fraction
is converted into a series of petroleum fractions where each
one is a mixture of a limited num ber of hydrocarbons with a
specific range of boiling point. Fractions with a wider range
of boiling points contain greater numbers of hydrocarbons.
All fractions f rom a distillation co lumn have a kn own boiling
range, except the residuum for which the upper boiling point
is usually not known. The boiling point of the heaviest com-
pon ent in a crude oil is not really known, but it is quite high. 60
The problem of the nature and properties of the heaviest com-
pounds in crude oils and petroleum residuum is still under
investigation by re searche rs [i 6, 17]. Theoretically, it can be
assumed that the boiling point of the heaviest compone nt in a
crude oil is infinity. Atmosp heric residue has com pou nds with 50
carbon number greater than 25, while vacuum residue has
compoun ds with carbon nu mber greater than 50 (M > 800).
Some of the petroleum fractions produ ced from distillation
columns with their boiling point ranges and applications are 40
given in Table 1.3. The boiling point and equivalent ca rbon
number ranges given in this table are approximate and they
may vary according to the desired specific product. For ex-
ample, the light gases fraction is mainly a mixture of ethane, E
-
(C5+) may exist in this fraction. The fraction is further frac- o
tionated to obtain ethane (a fuel gas) and propane a nd butane
(petroleum gases). The petroleum gases are liquefied to get
liquefied petroleum gas (LPG) used for home cooking pur-
poses. In addition the isobutane may be separated for the gas 20
mixture to be used for improving vapor pressure characteris-
tics (volatility) of gasoline in cold weathers. These fractions
may go through further processes to produce desired prod-
ucts. For example, gas oil may go thro ugh a crackin g process 10-
to obtain more gasoline. Since distillation is not a perfect sep-
aration process, the initial and final boiling points for each
fraction are not exact and especially the end points are ap-
proximate values. Fractions may be classified as narrow or
wide depend ing on their boiling point range. As an example, 0
the composition of an Alaska crude oil for various products 0
is given in Table 1.4 and is graphically shown in Fig. 1.3.
The weight and volume percentages for the products are
near each other. More than 50 of the crude is proces sed
in vacuum distillation unit. The vacuum res iduum is mainly
resin and asphaltenes-type compounds composed of high
molecular weight multiring aromatics. The vacuu m residuum
may be mixed with lighter products to produce a more valu-
able blend.
Distillation of a crude oil can also be perf orme d in the lab-
oratory to divide the mixture into ma ny narrow boiling point
range fractions with a boiling range of about 10~ Such nar-
row range fractions are sometimes referred to as
petroleum
cuts When boiling points of all the cuts in a crude are known,
then the boiling point distribution (distillation curve) of the
t m o s p h e r i c D i s t i l l a t i o n 46.1
Light
Gas O i l
Gas O il
Residuum
o
V a c u u m D i s t i l l a t i o n 53.9 '/o
i i
. 6 5 5
1
V o l u m e P e r c e n t
Light Gases ~ Ligh tGaserine
 
Total Crude
1. I N T R O D U C T I O N 9
TABLE 1.4--Products and c omposition o f alaska crude oil.
Approximate boiling range
C2 C4 --90 to 1 --130-30 1.2 0.7
C4-C7 -1-83 30-180 4.3 3.5
C7 Cll 83--205 180--400 16.0 14.1
Cll C16 205-275 400-525 12.1 11.4
C16 C21 275-345 525-650 12.5 12.2
C2-C21 -90-345 -130-650 46.1 41.9
C21-C31 345-455 650-850
>C48 655+ 1050+
C21-C48+ 345-655+ 650-1050
C2-C48+ -9(P655+ -130-650+
Information given n this table has been extracted from Ref. [19].
aBoiling ranges are interconverted o the nearest 5~ (~
20.4 21.0
15.5 16.8
18.0 20.3
53.9 58.1
100.0 100.0
whole crude can be obtained. Such distillation data and their
uses will be discussed in Chapters 3 and 4. In a petroleum
cut, hydrocarbons of various types are lumped together in
four grou ps of paraffins (P), olefins (O), naphth enes (N), and
aroma tics (A). For olefin-free petro leum cuts the co mposi-
tion is represented by the PNA content. If the composition
of a hydrocarbon mixture is known the mixture is called a
defined mixture while a petroleum fraction that has an un-
known co mposition is called an undefined fraction.
As menti oned earlier, the petrol eum fractions presen ted
in Table 1.3 are not the final products of a refinery. They
go through further physicochemical and finishing processes
to get the characteristics set by the market and government
regulations. After these processes, the petroleum fractions
presented in Table 1.3 are converted to petroleum products.
The terms petroleum fraction, petroleum cut, and petrole um
product are usually used incorrectly, while one should re-
alize that petroleum fractions are products of distillation
columns in a refinery before being converted to final pro