PETROLEUM SYSTEMSOURCE, GENERATION,

MIGRATION, TRAPS

SYED ABU HURERAMUHAMMAD FARHAN ASLAM

SALMAN AHMED

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PETROLEUM SYSTEMS

Source RockMigration RouteReservoir RockSeal RockTrap

Elements

PreservationGenerationMigrationAccumulation

Processes

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PETROLEUM SYSTEM PROCESSES

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Petroleum System ElementsPetroleum System Elements

120° F120° F

350° F350° FGenerationGeneration

MigrationMigration

Seal RockSeal Rock

Reservoir RockReservoir Rock

OilOil

WaterWater

Gas CapGas Cap

EntrapmentEntrapmentAccumulation

Source Rock

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ORIGIN OF PETROLEUM

• Petroleum is formed from the organic matter

phytoplankton's Microscopic floating animals in the sea

Algae (animals). land plants on the coast .• The organic matter is buried

under the layer of the sediment brought by the rivers and deposited in the sea

• The organic matter decays during the time the thick layers of Sediments are piled upon it.

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THE ORIGIN OF PETROLEUM

Organic-richSource Rock

Thermally MaturedOrganic Matter Oil

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SEDIMENTARY BASIN• Sedimentary basin are large subsiding depressions filled

with thick sequence of sedimentary rocks. These depressions result from the compression or extension of tectonic plates of the earth.

• There are around 600 sedimentary basins in the world, only 40% are producing.

• Petroleum is found in the sedimentary basins.• The floor of the basin is made up igneous and metamorphic

rocks and is often called “basement complex” • Two sedimentary basins in Pakistan• Indus basin • Baluchistan basin

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SEDIMENTARY ROCK

• Sedimentary rocks are composed of sediments. That is, particles such as grains that are formed by the breakdown of the preexisting rocks. Or sea shell fragment Or salts precipitated from ocean water.

• The most common organic sedimentary rock is black shale..• Sedimentary rocks are of two type1. Those which have formed by deposition of granular

material brought from land to depositional basin called Clastic Rocks.

2. Those which form because of precipitation of salts from oversaturated saline sea water called Non- Clastic or chemical rocks.

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TYPES OF SEDIMENTARY ROCKS

• (Detrital or clastic) Conglomerate or Breccia Sandstone Siltstone Shale

• Chemical/biochemical Evaporites

• Carbonate sedimentary rocks (limestone and dolostone)

Siliceous sedimentary rocks • Organic (coals)

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SEDIMENTARY ROCKS FORM BY A SUCCESSION OF PROCESSWeathering of pre-existing rocks

↓Erosion of weathering rocks

↓Transportation of weathered and eroded (clastical) material

↓Deposition of clastic material in an ocean basin serving as (sedimentary basin)

↓Compaction of clastic particulate of material as layer of sediment

↓Cementing of grains by salts precipitating around grains.

↓Digenetic changes (some chemical reactions, crystallization)

↓Conversion of sediments into sedimentary rocks.

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 SOURCE ROCK 

The source rocks are mainly organic rich

shale, which are very fine grained and

impermeable . These are microscopic marine

algae, which live in the upper layers of the

ocean and on death, sink in countless millions

to the sea floor. There the algae become the

part of the sediment and form organic rich

marine shale. These shale have the potential

to generate petroleum and are termed as

Source Rock.

SHALE ROCK

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MATURATION

• The conversion of organic matter into petroleum is termed as Maturation. As the organic-rich sediment is buried and subjected to slightly increased pressure and temperature the organic matter is converted into Kerogen.

• The type of maturation depends on the organic matter. Three kinds of kerogen have been identified • Type-I Digenesis --------derived from marine Algae• Type –II Catagenesis ------- derived from a mixture of marine

organisms• Type-III Metagenises ------ from terrestrial flora.

Type II is the main source of Crude oil(temp maximum 60˚C depth7000 feet) Type III gives rises to natural gas (temp maximum 150˚C depth 18000 feet)

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MIGRATION• Migration is the process of the oil and gas moving away

from the source rock.

• This is a slow process. Migration is caused by burial,

compaction, and increase in volume and separation of the

source rock constituents .

Primary Migration — The movement of

hydrocarbons out of the source rock.

• Secondary Migration —Secondary migration into within

rocks where it is accumulates, which are called reservoir

rocks.

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RESERVOIR ROCKS

• Oil and gas generated in the source rock must be expelled out and migrate to a porous and permeable rock where it can be stored.

• Porosity: Billion of tiny spaces between grains of sedimentary rocks, expressed as %

• Permeability: The ease with which fluids flow in the rock when the pores are connected.

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• Sandstones: Sandstone are common reservoir rocks for petroleum and hold 60% of the world recourses.

Limestone. A limestone behaves as a good reservoir rock only where a secondary porosity is produced in the rocks

Sandstone

Limestone

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Porosity values for an oil reservoir

• 0-5% Insignificant• 5-10% Poor• 10-15 Fair• 15-20 Good• 20-25 Excellent

Permeability values for an oil reserve

• 1-10md poor• 10-100md Good• 100-1000md Excellent

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TRAP• Hydrocarbons within the reservoir rock move towards a

high point(trap) in the reservoir to accumulate in a pool. It is configuration of rocks suitable for containing hydrocarbons and sealed by a relatively impermeable formation through which hydrocarbons will not migrate.

TYPES OF TRAPS• There are three basic types of traps

• 1-Anticlinal traps: result of compression of strata and are the most common traps. The largest oil and gas fields of the world are in anticline and dome.

• 2-Faults: May form a pool by sealing porous strata in extensional tectonics.

• 3-Stratigraphic traps: those where impermeable strata seal the permeable reservoir. It is formed by changes in rock type unconformities, or sedimentary features such as reefs.

Fault trap

Anticline trap

Unconformity

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SEAL (CAP ROCK)• A relatively impermeable rock that forms

a barrier, cap or seal above and around reservoir rock so that fluids cannot migrate beyond the reservoir. The permeability of a cap rock must equal to zero.

• Some examples are Shale, Evaporites such as Anhydrite ,Salt, & Zero-porosity Carbonates.

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Gypsum

Anhydrite

THANK YOU

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