Petroleum, also known as crude oil, is a naturally occurring liquid found beneath the Earth's surface. It is composed primarily of hydrocarbons such as carbon and hydrogen. Crude oil is extracted from the ground through oil wells, either because it flows naturally due to underground pressures or through mechanical pumping. There are several theories for the origin of petroleum, but the modern theory is that it formed from the decomposition of marine organisms and terrestrial plant material over millions of years. Once extracted, crude oil undergoes processing to remove impurities and separate it into useful petroleum products through distillation. These products include fuels like gasoline, diesel and jet fuel, as well as other commodities like lubricating oils, asphalt and

2. Also called as rock oil.
 Naturally occurring oil and the colour varies from
black to brown.
 Either petroleum oil flows out itself (due to
underground pressure)
 Or it is pumped out mechanically.
COMPOSITION OF PETROLEUM
OIL:
 Typical composition of petroleum is as Element %age
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carbon
84-87
hydrogen
11-15
nitrogen
0.1-1.5
oxygen
0.3-1.5
sulphur
0.1-3

3. Difference between origin
of petroleum oil and coal
Formations
Petroleum oil is formed from sea plants and animals decaying
under strongly reducing conditions.Coal is formed mainly from
land plants decaying under mildly reducing condition
 Nature of seams:
Coal seams remain static while oil seams can migitate under the
effect of pressure and temperatures
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4. Origin of Petroleum
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Widely accepted theories for origin of petroleum are
Carbide Theory:
Hydrocarbons present in petroleum are formed by the action of
water or inorganic carbides
Inoganic carbides are formed by reaction of metal & carbon
under high temperature and pressure inside the earth
Ca + 2C = CaC2
Al + C = Al4C3
These carbides would react with underground water to form
hydrocarbons
CaC2 +2 H2O = Ca(OH)2 + C2H2 (acetylene)
Al4C3 + 12 H2O= 4Al(OH)3 + 3CH3 (methane)

5. Contd.
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Lower hydrocarbons then undergo hydrogenation
and polymerization.
C2H2 + H2 = C2H4 +H2 = C2H6
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3C2H2 = C6H6 (benzene)
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3C2H4 = C6H12 (cyclohexane)
Flaws In Carbide Theory:
This theory fails to explain the following facts.
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presence of nitrogen and sulphur compounds.
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presence of chlorophyll.
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presence of optically active compounds
Due to these flaws this theory was rejected.
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6. Englar Theory
Suggested by Englar in 1900 that petroleum is of animal
origin.
 Formed by the decay and decomposition of marine animals
under high pressure and temperature.
 SO2 was given by volcano deside the sea-side kills the fish
and other marine animals which go in to piling.
 Hundreds of year causes animalto decompose under high
pressure and temperature to form petroleum
this theory was supported by the facts as
 destructive decomposition of fish, oil and other animals
fats under high P & T, gives product similar to petroleum
 presence of brine and sea water along with petroleum
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Presence of fossils in the petroleum
areas.
However this theory fails to explain the
presence of chlorophyll in petroleum as
well coal deposit in the vicinity of oil
field.

8. Modern Theory
According to modern theory
Petroloeum is believed to formed from the
decomposition of marine animals as well as of
vegetable organism of prehistoric forests.
 prehistoric forests and sea animals got burried
under the crust of earth due to some earthquakes
and upheavals .
 High T & P in earth crust causes the
degradation of biological matter in to petroleum.
This theory succesfully explain the flaws present in
previous theoris like
 Presence of brine & coal in yhe vicinity of
petroleum
 Presence of chlorophyll & N and S compoounds
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9. Detection Of petroleum
Deposits
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Detection of petroleum include the steps as following.
Visual method
Geophysical method
Geological method
Drilling method
Visual method include oil seepages at the surface of earth.
Geophysical method include measuremet of density,
elasticity magnetic & electrical properties of the rocks
Geological method include the measurement of age &
nature of rocks inside the earth’s crust
Drilling is the final test when the petroleum deposit has been
proved by the earlier methods.

10. Contd.
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Petroleum always occur along with gas (natural gas)
After drilling,both natural gas and oil flow up through
the pipe under pressure.
Ater the decreasing of pressure, residual oil is sucked
by a pump or pressure is created by injecting
compressed gas or high preesure water through bored
pipe to drill it out.
Oil well containing both oil& gas= wet well.
Oil well containing gas = dry well.

11. Pretreatment Of Oil At Oil field
Oil and gas from field are separated.
 Natural gas is compreesed to liquify it used for house hold
purposes.
 Petroleum oil is made free of water sediments and salts
 Then dissolved gases are removed from it by a process
called stabilization.
 Then sent to oil refineries for separation in to various
petroleum products by distillation and other operations
Mechanical Method:
oil is subjected to centrifuging, filtration and settling after
heating it to 120-160 C at 6-8 atm pressure.
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12. Contd.
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Physico-chemical method:
In this method emulsion breakers but they are costlyand cause
corrosion and sludge formation.
Electrical dehydration method:
10% water is added to crude and heated before passing
through an electrical dehydrator.
In dehydrator two concentric metal plates are electrode in
which 30000 volt is supplied separating water from crude.
1st dehydrator => T= 90-95C , P=6.8atm
2nd dehydrator => T= 80-90C, P=5.5-6atm.

13. Stabilization Of
Crude Oil
•Stabilization is the method to remove dissolved gasses from
crude oil.
•Gas must be removed to avoid breathing loss(loss of gasoline,
if gas is not removed from oil during pre-refining).
•Breathing loss is due to change of humidity of ambient air and
day and night tempereture during filling and emptying of crude
tanker.
•Breathing loss= 0.4-0.75 kg/m3 permonth.

14. Classification of Petroleum
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Depending on nature, hydrocarbon are classified as
Paraffinic crude petroleum oil
Naphthenic crude petroleum oil
Asphaltic (aromatic) crude oil
Mixed crude oil
paraffins have general formula Cn H2n+2 are saturated
hydrocarbons (where n=1 to 35) such as methane, propane,
pentane.
Naphthenes having general formula CnH2n are saturated
ring compounds (where n=1 to 9) e.g cyclobutane (C4H8),
cyclohexane (C6H12) etc.
Another hydrocarbons having same general formula
CnH2n but straight chain is called olefin. E.g ethylene
(C6H6), toulene (C6H5CH3) etc.

15. Contd.
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Aromatics have general formula C6H2n-6 (n>6)
contain 6 carbon atoms in the form of hexon
shaped ring and are unsaturated ring
compounds
Lower hydrocarbons in these groups are
generally gases, intermediate ones are liquids
and higher ones are solids/semi solids.

16. Uses of Petroleum Products
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Liquified petroleum gas(LPG):
Mixture of propane and butane
Domestic and industrial fuel
Al so called refinary gas.
Gasoline (petrol):
Fuel for sparking ignition & internal combustion engine
Dry cleaning of clothes
Naphtha:
Used as paint thinner, solvents, blending of motor fuel
Used in production of H2 by its steam reforming.
Used as a fuel gas in steel plants.

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Jet fuel:
Fuel for jet planes, motor engines.
Diesel:
Fuel for diesel engine
Gas oil:
Gassified for fuel gas production
Fuel for industrial funace
Used as a blend for heavy fuel oil.
Lubricating Oil:
Used as lubricants in machines and engines.
Petrolatum:
Also a lubricant used as a base material for grease manufacture
Light fuel oil:
Used as a fuel in industrial furnace.

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Heavy fuel oil:
Used as furnace fuel after blending with light
fuel oil
Cracked to produce gasoline, diesel, gas, light
fuel etc.
Bitumen or Tar:
Used for road making as a binder
And for moisture proof coating
Wax:
Used for making candles
Used for match stick coating,

19. Queries?