Petroleum, or oil, is a naturally occurring hydrocarbon that is formed from the remains of ancient organisms over millions of years. It is composed primarily of carbon and hydrogen, along with smaller amounts of other elements. There are different types of hydrocarbons that make up petroleum, with paraffin being the most common at 30%. Petroleum is formed through a process called diagenesis where organic matter buried deep underground is exposed to high temperatures and pressures over long periods of time. As it forms, petroleum may migrate upward through porous and permeable reservoir rocks until it is trapped by an impermeable cap rock in a structure known as an oil trap. The main reservoir rocks that can store petroleum are sandstone and

1. Group 01
Mineral Resources and Technology
1

2. What is petroleum?
 Naturally occurring hydro carbon.
2 PETROLEUM
Major
C , H
Minor
O , S , N
Hydrocarbon Average
Paraffin's 30%
Naphthenes 49%
Aromatics 15%
Asphaltic 6%
Table 01: Composition of hydrocarbons by weights

3. Hydrocarbon Generation3
Two major phases of oil
generation:
 Oil window
• 100-150 °C 2.5-4.5 km
 Gas window
• 150-230°C

4. Countries where petroleum is produced4
• OPEC Countries – 42%
• Russia – 13%
• United States – 12%
• China – 5%
• Other oil producing
countries – 17%

5. Uses of Petroleum5

6. Formation of Petroleum
 Petroleum Systems
 Key Words
 Porosity
 Permeability
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Elements Processes
Source Rock Generation
Migration Route Migration
Reservoir Rock Accumulation
Seal Rock (Trap/ Cap Rock) Preservation

7. How Petroleum was formed?????7
Small
Organisms-
Planktons
Algae, Bacteria
T,P,W Extraction

8. How petroleum was created cont’d…,
 Pre-historic planktons (zoo planktons, Phytoplankton) were preserved in
the ocean basins.
 Eg:- Diatoms, Foraminifera, Radiolarian, Benthic algae
 OM mixed with mud were buried and covered with sediments.
 Temperature, Pressure, increased with depth.
 Chemical changes were occurred.
 Mainly under 3 steps
 Diagenesis- Sediments sedimentary rocks
 Catagenesis - Oil & gas formed
 Metagenesis
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Phy, Chem, Bio

9. Kerogen
 Insoluble waxy substance derived from organic matter
 Algae, Wood, Pollen, Vitrinite etc..
 Found in various oil shale.
 Four kerogen types
 Contain different amount of H relative to O and C
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Kerogen Type Hydrocarbon Potential Amount of H
i Crude oil prone Higher
ii Crude oil & Natural gas prone Moderate
iii Gas prone Low
iv Inert material . Non-Prone None

10. Source Rock
 What is source rock?
 Sedimentary rock
 Contains sufficient organic matter (Hydrocarbons)
 Fine Grained
 When buried and heated, produce petroleum
 Preferable Conditions
 High productivity
 Stagnant Water Body
 Anoxic Conditions
 Swamps, Shallow seas, Coastal Upwelling, Lakes
 Quality depend on;
 Abundance of Organic Matter (OM)
 Preservation Potential
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11. Source Rock contd…
 Abundance of OM is determined by;
 Amount of Light, Water depth, Latitudes, Water temperature, Water turbidity, Abundance
of nutrients preferred by plants
 Preservation Potential (Conditions that favour the preservation of OM)
o Two important conditions
• Anaerobic conditions, Rapid sedimentation
• Maturity of Source rock is important to form oil / Gas
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12. Maturity of Source Rock
 Maturity?????
 Ability of the source rock to produce oil and (or) gas
 Depends on;
 Temperature and Pressure
 Age of source rock (At least 20 Ma)
 Maturity is measured by;
 Vitrinite Reflectance (R0)> 0.55
 TOC ( Total Organic Carbon) > 1 wt.%
 Oil / Gas formed by matured rock migrates.
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13. Reservoir Rock
 An element of petroleum system that can accumulate hydrocarbon. Rocks are able to
store the fluids (water, oil and gas) inside its pores.
 Reservoir rock must has good porosity and permeability to accumulate oil in
economical quantities.
 Petroleum is ultimately collected through secondary migration in reservoir rock.
 Reservoir rock types most frequently in oil field are sand stone and carbonates
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14. Migration
Primary Migration Secondary Migration Tertiary Migration
Migration of
generated oil / gas
within the source
rock
Migration of generated
oil / gas beyond the
source rock
Leakage of
petroleum to the
earth’s surface due
to absence of trap.
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• The process which petroleum moves from source rock to it’s final destination,
through carrier beds.
• Migration medium- Porous, high permeability
• 3 stages in migration process;

15. Cap Rock/ Seal Rock/ Trap rock15
 Oil and gas are less denser than water. Hence rise upward under buoyancy.
 Further migration of oil / gas is prevented by seal rock.
 Cap rock is an impermeable rock
 Eg:- Shale, Mud stone, Silt stone
 Perfect cap rocks can not be found(100% impermeable)
 Minor cracks might present

16. Types of traps16

17. Timing of petroleum migration
 Timing of petroleum migration is important.
 Relative to the deposition of
 reservoir rock
 seal rock
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1 Source Rock
2 P/T Not a petroleum system
3 Sand Stone
1 Source Rock
2 Sand Stone
3 Mud Stone Petroleum system
4 P/T

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19. Group Members
 Athputhan S.
 Balasooriya I.A.
 Bandara T.G.T.A.
 Bogahawatte P.M.B.M.V.
 Chiranjaya Y.A.S.U.
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UWU/MRT/15/001
UWU/MRT/15/002
UWU/MRT/15/003
UWU/MRT/15/004
UWU/MRT/15/006