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LOGO
Petroleum Geology
Reservoir rock properties coursePeyman Maroufi
Petroleum Geoscience department
Soran university
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What is petroleum
What is petroleum
Petroleum is a mixture of naturally occurring hydrocarbons whichmay exist in the solid, liquid, or gaseous states, depending upon the
conditions of pressure and temperature to which it is subjected.
Whereas natural gas contains a few lighter hydrocarbons, both crudeoil and tar deposits may consist of a large number of different
hydrocarbons.
1) Liquid Hydrocarbons: Crude oil or Petroleum
2) Gas Hydrocarbons: Natural Gas: methane,
butane, propane, etc.
3) Solid Hydrocarbons: Tars and Asphalt
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What is petroleum
Virtually all petroleum is produced from the earth in either liquid or gaseous form,
and commonly, these materials are referred to as either crude oil or natural gas,
depending upon the state of the hydrocarbon mixture.
Petroleum consists chemically of approximately 11 to 13 wt % hydrogen and 84 to
87 wt % carbon.
Traces of Oxygen, Sulfur, Nitrogen, and Heliummay be found as impurities in crudepetroleum.
Although all petroleum is constituted primarily of carbon and hydrogen, the
molecular constitution of crude oils differs widely.
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Chemistry of Petroleum
Hydrocarbons:
In organic chemistry, a hydrocarbon is an organic
compound consisting entirely of hydrogenand carbon
atoms.
The simplest
hydrocarbon isMethane (CH4)
The classifications for hydrocarbons:
1) Saturated hydrocarbons (alkanes)
2) Unsaturated hydrocarbons
3) Cycloalkanes4) Aromatic hydrocarbons
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Chemistry of Petroleum
1) Saturated hydrocarbons (alkanes):
Saturated hydrocarbons (alkanes) are the simplest of the hydrocarbon speciesand are composed entirely of single bonds and are saturated with hydrogen.
The general formula for saturated hydrocarbons is:
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Chemistry of Petroleum
1) Saturated hydrocarbons (alkanes):
Saturated hydrocarbons are the basis of petroleum fuels andare found as either linear or branched species.
These alkane also are calledparaffin hydrocarbons.
Petroleum engineer normally call theseparaffins.
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Chemistry of Petroleum
2) Unsaturated hydrocarbons:
Unsaturated hydrocarbons have one or more double or triple bondsbetween carbon atoms.
A) alkenes:
The distinguishing feature of the alkene structure is thecarbon-carbon double bond.
The general formula for the alkene family is:
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Chemistry of Petroleum
A) alkenes:
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Chemistry of Petroleum
B) alkynesThose containing triple bonds are called alkynes, with general formula
2) Unsaturated hydrocarbons:
Unsaturated hydrocarbons have one or more double or triple bondsbetween carbon atoms.
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Chemistry of Petroleum
3) Cycloalkanes
Cycloalkanesare hydrocarbons containing one or more carbon rings to
which hydrogen atoms are attached.
The general formula for a saturated hydrocarbon containing one ring is:
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Chemistry of Petroleum
The cycloalkanes also are known asNaphthenes, Cycloparaffins, or
alicyclichydrocarbons.
In the petroleum industry, this class of hydrocarbons is known as
Naphthenes. Naphthenes have saturated rings.
3) Cycloalkanes
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Chemistry of Petroleum
4) Aromatic hydrocarbons:Aromatic compounds (also called arenes) include benzene
and compounds that resemble benzene in chemical behavior.
Benzene:Benzene, C6H6, is the simplest aromatic hydrocarbon and was recognized as the
first aromatic hydrocarbon
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Non hydrocarbon Components of Petroleum
Petroleum also contain compounds:
1) Sulfur Compounds.
2) Nitrogen
3) Oxygen
4) Little metals
Common non hydrocarbon constituents of petroleum
are:
1) Nitrogen ()2) carbon dioxide ()
3) hydrogen sulfide ()
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Chemistry of Petroleum
Resins and Asphaltenes
The chemicals in petroleum are classified as:
1) Paraffins
2) Naphthenes
3) Aromatics
4) Resins-asphaltenes
Resins and asphaltenes are large molecules, primarily hydrogen and carbon,
with one to three sulfur, oxygen, or nitrogen atoms per molecule.
The basic structure is composed of rings, primarily aromatic, with from three to
ten or more rings in each molecule. The non hydrocarbon atom can be a part ofthe ring structure or can be located in links connecting the rings.
The color of petroleum is determined largely by the quantity of resinsand
asphaltenespresent, although the greenishcast of some crude oils is probably
due to the presence of molecules containing six or more rings.
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Chemistry of Petroleum
The exact molecular composition varies widely from formation to formation
but the proportion of chemical elementsvary over fairly narrow limits as
follows:
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Composition of petroleum
Average and Range of Hydrocarbon series molecules in Crude Oil
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Composition of petroleum
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Composition of petroleum
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Origin of petroleum
The theories of the origin of petroleum may be classified as:
1) Organic
2) Inorganic
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Origin of petroleum
Origin of petroleum:
1) Organic theories:
The organic theories assume that petroleum evolved fromdecomposition of vegetable and animal organisms that lived during
previous ages.
2) Inorganic theories:The inorganic theories attempt to explain the formation of petroleum by
assuming chemical reaction among water, carbondioxideand various
inorganicsubstances such as carbides and carbonates, in the earth.
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Origin of petroleum
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The Origin and Habitat of Petroleum
Accumulation of Oil and Gas
The accumulation of economic volumes of petroleum (oil and/or gas) in the
subsurface requires that several essential geological elements and processes
be present at specific time and space.
The essential elements of a petroleum system include the following:
1) Source rock
2) Reservoir rock
3) Migration
4) Traps
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The Origin and Habitat of Petroleum
To have a petroleum accumulation it is necessary to have source rock and a
reservoir or storage bed
Source rock:
Source rocks generate and expel petroleum when sufficient thermal energy is
imparted to the sedimentary organic matter (kerogen) to break chemical bonds.
This heating is induced usually by burial by overburden rock.
Reservoir rock:
A subsurface body of rock having sufficient porosity and permeability to store and
transmit fluids.
A suitable reservoir rock is porous and permeable. That is , the pores interconnect
so that fluids can migrate through the rock.
Sedimentary rocks are the most common reservoir rocks because they have more
porosity than most igneous and metamorphic rocks and
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The Origin and Habitat of Petroleum
Migration of petroleum :
The movement of hydrocarbons from their source into reservoir rocks.
1) Primary migration
2) Secondary migration
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The Origin and Habitat of Petroleum
1) Primary migration:
The movement of newly generated hydrocarbons out of their source rock is
primary migration, also called expulsion.
2) Secondary migration:
The further movement of the hydrocarbons into reservoir rock in a
hydrocarbon trap or other area of accumulation is secondary migration.
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Traps
As oil and gas are lighter than the ground water which permeates the porous rocks
below the water table, it is evident that the upward movement of petroleum must be
restricted in order that accumulations exist at depth
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Traps
Classification of Hydrocarbon Traps
1) Structural traps :Structural traps are traps that are formed because ofa deformation in the rock layer that contains the hydrocarbons.
a) Anticlinal traps: an upward fold in the layers of rock
b) Fault traps: A fault trap occurs when the formations on either side ofthe fault have been moved into a position that prevents furthermigration of petroleum.
c) diapiric traps: produced by intrusion of salt or mud diapirs
2) Stratigraphic traps: result when a depositional bed changes frompermeable rock into fine-grain impermeable rock
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Traps
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Traps
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The Origin and Habitat of Petroleum
GENERATION, MIGRATION, AND
TRAPPING OF HYDROCARBONS
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Types of Rocks
Igneous Rocks about 20% of all rocks they are the product of the cooling of molten magma
intruding from below the mantle of the crust.
Metamorphic rocks about 14% of all rocks originate from mechanical, thermal, and chemicalchanges of igneous rocks
Sedimentary Rocks
about 66% of all rocks they are important to the study of petrophysics andpetroleum reservoir engineering.
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Sediments and Sedimentary Rocks
What are sediments?
Sediment- loose, solid particles originating from:
Weathering and erosion of pre-existing rocks Chemical precipitation from solution, including secretion by
organisms in water
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Sediments and Sedimentary Rocks
What is a Sedimentary Rock?
Sedimentary rocksare types of rockthat Sediments after they
are deposited may be buried and undergo physical andchemical change resulting in a solid rock.
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Sediments and Sedimentary Rocks
The three most common sedimentary rocks associated
with petroleum reservoirs are:
1) sandstone
2) shale
3) limestone.
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Sedimentary Rock Types
Siltstone, mudand shale
~75%
Relative abundance
Sandstone
and conglomerate~11%
Limestone and
dolomite~13%
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Dimension and Units
Dimension: A dimension is the measure by which a
physical variable is expressed quantitatively.
Unit: A unit is a particular way of attaching a number
to the quantitative dimension.
For example: length is a dimension associated with
such variables as distance, displacement, width,
deflection, and height, while centimeters and inchesare both numerical units for expressing length
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Dimension and Units
Dimensions:
1) primary dimensions
2) secondary dimensions
primary dimensions :
In fluid mechanics there are only fourprimary dimensions fromwhich all other dimensions can be derived: mass, length, time,
and temperature.
Dimension of mass = [M]
Dimension of length= [L]
Dimension of time = [T]
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Dimension and Units
secondary dimensions:
A secondary dimension is one that is formed by combining
primary dimensions. For example:
Dimension of length:
force,: which is directly related to mass, length, and time by Newtons second law
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Dimension and Units
Systems of Units
Systems of units have always varied widely from country to country, even
after international agreements have been reached.
British Gravitational (BG) System:
In the BG system:
unit of length is: foot (ft) time unit is: second (s)
The mass unit: slug
force unit is: pound (lb)
temperature unit is: degree Fahrenheit (F)
or
absolute temperature unit is: degree Rankine (R) R + 459.67
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Dimension and Units
Newtons second law:
1 (1 ) (1
)
This relationship indicates that a 1-lb force acting on a mass of 1 slug will
give the mass an acceleration of 1
The weight, W (which is the force due to gravity, g) of a mass, m, is given by
the equation:
() () (
)
Since the earths standard gravity is taken as: commonly approximated as
32.174
32.2
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Dimension and Units
International System (SI).
unit of length is: meter (m)
time unit is: second (s)
The mass unit: kilogram (kg)
force unit is: newton (N)
temperature unit is: kelvin degree (K)
The Kelvin temperature scale is an absolute scale and is related to the Celsius
(centigrade) scale (C) through the relationship:
K + 273.15
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Dimension and Units
The force unit, called the newton (N), is defined from Newtons second law as
1 (1 ) (1
)
Standard gravity in SI is:
9.807
9.81
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Dimension and Units
Prefixes for forming multiples and fractions of SI units
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Dimension and Units
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Dimension and Units
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Physical properties of Hydrocarbons
Viscosity
Density
Spesific gravity
API
Ph i l i f H d b
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Physical properties of Hydrocarbons
Density:
Density is an extremely important property of matter.
The density of a fluid (or any other form of matter) is the amount of mass
per unit volume.
Dimensions:
Units:
;
;
Density is highly variable in gases and increases nearly proportionally to the
pressure level. Density in liquids is nearly constant. at C and atm:
Water: 1000 kg/m3;
Mercury: 13546 kg/m3;
Air: 1.23 kg/m3;
Paraffin: 800 kg/m3.
Ph i l ti f H d b
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Physical properties of Hydrocarbons
Specific gravity:
Specific gravity, denoted by SG.
Specific gravity is defined as the ratio of the density of a fluid to the density of some
standard fluid at a specified temperature and pressure.
Commonly standard fluid for liquids is Waterand for gasses is Air.
Specific gravity for gases
Specific gravity for liquids
Ph i l ti f H d b
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Physical properties of Hydrocarbons
Specific gravity of gases:
P=14.7 psi = 101.325 kPa =1atm
atT= 60 F = 15 F = 288.15 K
1.225 0.076
0.076
Physical properties of Hydrocarbons
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Physical properties of Hydrocarbons
Specific gravity of Crude Oil:
P=14.7 psi = 101.325 kPa =1atmat
T= 60 F = 15 F = 288.15 K
999 62.4
62.4
The specific gravity of crude oils ranges from
about 0.75 to 1.01.
Physical properties of Hydrocarbons
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Physical properties of Hydrocarbons
The American Petroleum Institute gravity, orAPI gravity
Although the density and specific gravity are used extensively in the petroleum
industry, the APIgravity is the preferred gravity scale. This gravity scale is precisely related to the specific gravity by the following
expression:
141.5
131.5
Conversely, 141.5
+ 131.5
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Crude Oils
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Crude Oils
Light Crude
Palo Pinto FieldNorth Texas
Light Crude
Palo Pinto FieldNorth Texas
Heavy Crude
Humble Oil FieldSouthwest Texas
Heavy Crude
Humble Oil FieldSouthwest Texas
Physical properties of Hydrocarbons
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Physical properties of Hydrocarbons
Viscosity:
The viscosity of a fluid is a measure of the internal fluid friction (resistance) to
flow.
If the friction between layers of the fluid is small, i.e., low viscosity, an applied
shearing force will result in a large velocity gradient.
As the viscosity increases, each fluid layer exerts a larger frictional drag on the
adjacent layers and velocity gradient decreases.
Symbols: o, g, wUnits: cp
Range and typical values
0.25 to 10,000 cp, Black oil
0.5 to 1.0 cp, Water
0.012 to 0.035 cp, Gas
Physical properties of Hydrocarbons
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Physical properties of Hydrocarbons