This document provides an overview of fundamental reservoir fluid properties and concepts. It discusses sampling and analyzing reservoir fluids, classifying hydrocarbons and their phase behaviors. Key fluid properties like gas, liquid, and formation water characteristics are examined. Common hydrocarbon types and compositions in crude oil and natural gas are also outlined. Fundamental reservoir engineering concepts involving hydrocarbon reserves calculations and fluid flow are reviewed.

1. FUNDAMENTAL RESERVOIR FLUID PROPERTIES
Ekeh Modesty Kelechukwu
Dept. of Chemical & Petroleum Engineering
UCSI University
56000 Cheras , Kuala Lumpur
ekehmodesty@ucsi.edu.my

2. Syllabus
Fundamental of Reservoir Fluid Behaviours
 Sampling and analysis of reservoir fluids
 Basic classification of hydrocarbons
 Hydrocarbon phase behaviours (single, double, multi-components)
 Classification of reservoir fluids
 Gas properties
 Liquid properties
 Formation water properties

3. Typical Reservoir
Gas
Oil
water

4. Hydrocarbon
Reservoir
Fluids: oil, gas and water
Typical Flow
Reservoir fluid must flow to the surface for
marketable oil and gas

5. Hydrocarbon Reserves
Np = A*h*f * Sw -Swi ( )* 1
Boi
- 1
Bo
æ
è
ç ö
÷
ø
1
G= A*h*f * ( 1- S)* ( B1 - -
B1
)
p wi B gi B
gi g
g

6. Oil or Gas or Mixture of Both
Pressure
Temperature
oil
gas
Oil + Gas
Bubble point

7. Fluid flow in reservoir
qw = kwA
m
Dp
DL
qo = koA
m
Dp
DL
qg =
kgA
m
Dp
DL
Saturated with oil, gas and water

8. Recovery optimization
separator
Oil reservoir

9. Sampling and analysis of reservoir fluids
 To obtain good equilibrium and representative reservoir fluid sample.
 Temperature and pressure changes influence equilibrium composition
of the gas and liquid phases.
Sampling Methods:
 separator surface sampling
 bottomhole sampling
Analysis Methods:
 PVT analysis
 HPHT
 Compositional analysis up to C70
 Constant composition expension
 Viscosity
 Differential liberation
 Compressibility

10. General properties of hydrocarbon fluids
 Formation volume factor, Bg, Bo, Bw: volres/volsc
 Density, specific gravity
 Isothermal Compressibility
 Viscosity
 Solution Gas-Oil Ratio
 Ideal gas law: pV = nRT
 Real gas law: pV = znRT

11. Typical composition of Petroleum Gases
Natural Gas
Hydrocarbons
Methane 70-98%
Ethane 1-10%
Propane trace - 5%
Butane trace - 2%
Pentane trace - 1%
Hexane trace - 0.5%
Heptane+ trace - 0.5%
Non-hydrocarbons
Nitrogen trace - 15%
Carbon dioxide trace - 5%
Hydrogen Sulfide trace - 3%
Helium up to 5%,
normally traces
or none

12. Typical composition of Petroleum Gases
Gas from Oil Well
Hydrocarbons
Methane 45-92%
Ethane 4-21%
Propane 1 - 15%
Butane 0.5 - 7%
Pentane v. little - 3%
Hexane v. little - 2%
Heptane+ v. little - 1.5%
Non-hydrocarbons
Nitrogen v. little – up to 10%
Carbon dioxide v. little - 4%
Hydrogen Sulfide v. little - 6%
Helium none

13. Typical Crude Oil Fractions
Crude oil fractions Boiling Chemical
Point, oF Composition Usages
Gas hydrocarbon C1 – C2 Fuel gas
up to 100 C3 – C6 Bottled fuel gas, solvent
Gasoline 100 – 500 C5 – C10 Motor fuel, solvent
Kerosene 350 – 480 C11 – C13 Jet fuel, cracking stock
Light Gas Oil 450 – 480 C13 – C17 Diesel fuel, furnace fuel
Heavy Gas Oil 580 – 750 C18 – C25 Lubricating oil, bunker fuel
Lubricant and Wax 750 – 950 C26 – C38 Lubricating oil, paraffin wax, petroleum jelly
Residual Oil 950+ C38+ Tar, roof compound, asphalt, coke

14. Typical composition analysis of crude oils
Carbon 84 - 87%
Hydrogen 11 - 14%
Sulfur 0.06 – 2%
Nitrogen 0.1 – 2%
Oxygen 0.1 – 2%

15. Basic classification of hydrocarbons
Hydrocarbon Homolog Series
Hydrocarbons
Alkenes
-unsaturated H
-olefin: 1 double bond
-diolefin: 2 double bonds
Alkanes (paraffin)
-saturated H
Aliphatic
Alkynes (acetylene)
-unsaturated H
-triple bonds
Aromatics
(Benzene)
Cyclic aliphatic
Naphthalene

16. Compounds in Crude Oil (South Ponca Field, Oklahoma)

17. Alkanes, CnH2n+2
No. of Carbon Name
1 Methane
2 Ethane
3 Propane
4 Butane
5 Pentane
6 Hexane
7 Heptane
8 Octane
9 Nonane
10 Decane
20 Eicosane
30 Triacontane
 Covalent bond: sharing electrons
 Isomerism - same molecular formula but
different structure, different physical and
chemical properties
 Prefix isomers – n-, iso-, neo-, etc.
Heptane C5 H12
 n-heptane
 iso-heptane
 neo-heptane

18. Alkanes, CnH2n+2
Physical properties:
Alkane Formula Boiling point [°C] Melting point [°C] Density [g·cm3]
(at 20°C)
Methane CH4 -162 -183 gas
Ethane C2H6 -89 -172 gas
Propane C3H8 -42 -188 gas
Butane C4H10 0 -138 gas
Pentane C5H12 36 -130 0.626(liquid)
Hexane C6H14 69 -95 0.659(liquid)
Heptane C7H16 98 -91 0.684(liquid)
Octane C8H18 126 -57 0.703(liquid)
Nonane C9H20 151 -54 0.718(liquid)
Decane C10H22 174 -30 0.730(liquid)
Undecane C11H24 196 -26 0.740(liquid)
Dodecane C12H26 216 -10 0.749(liquid)
Icosane C20H42 343 37 solid
Triacontane C30H62 450 66 solid
Tetracontane C40H82 525 82 solid
Pentacontane C50H102 575 91 solid

19. Nomenclature of Alkanes
Based on IUPAC (International Union of Pure and Applied Chemistry) rules:
Alkyl groups (missing one hydrocarbon atom): methyl group, ethyl group, prophyl group
These rules are as follows:
 The largest continuous chain of carbon atoms is taken as the
framework on which the various alkyl groups are considered to be
substituted. Thus the following hydrocarbon is a pentane.
 The parent hydrocarbon is then numbered starting from the
end of the chain and the substituent groups are assigned numbers
corresponding to their positions on the chain. The direction of
numbering is chosen to give the lowest sum for
the numbers of the side chain substituents. Thus, the
hydrocarbon is 2,3-dimethylpentane. .

20. Nomenclature of Alkanes
 Where there are two identical substituents in one position
as in the compound below numbers are supplied for each.
 Branched-chain substituent groups are given appropriate
names by a simple extension of the system used for branched
chain hydrocarbons. The longest chain of the substituent is
numbered starting with the carbon attached directly to the
parent hydrocarbon chain. Parentheses are used to separate
the numbering of the substituent and the main hydrocarbon
chain.
 When there are two or more different substituents present,
the common method is to list the substituents in alphabetical
order, although the substituents are sometimes listed in order
of increasing complexity.