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Petroleum system.pptx
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- 2. Source Rock Migration Route ReservoirRock Seal Rock Trap Elements Preservation Generation Migration Accumulation Processes 2
- 3. 2480 120° F 350° F Generation Migration SealRock Reservoir Rock Water Gas Cap Oil E En nt tr ra ap p Accumulation ment Source Rock 3
- 4. • Petroleum isformed 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. 4
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- 6. • Sedimentary basinare 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 6
- 7. • Sedimentary rocksare 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 type 1. 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. 7
- 8. • (Detrital orclastic) Conglomerate or Breccia Sandstone Siltstone Shale • Chemical/biochemical Evaporites • Carbonate sedimentary rocks (limestone and dolostone) Siliceous sedimentary rocks • Organic (coals) 8
- 9. Weathering of pre-existingrocks 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. 9
- 10. The source rocksare 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. 10
- 11. • The conversionof 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) 11
- 12. • Migration isthe 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. 12
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- 14. • Oil andgas 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. 14
- 15. Limestone. A limestonebehaves as a good reservoir rock only where a secondary porosity is produced in the rocks Limestone 15 • Sandstones: Sandstone are common reservoir rocks for petroleum and hold 60% of the world recourses. Sandstone
- 16. Porosity values foran oil reservoir • 0-5% • 5-10% • 10-15 • 15-20 • 20-25 Insignificant Poor Fair Good Excellent Permeability values for an oil reserve • 1-10md • 10-100md • 100-1000md poor Good Excellent 16
- 17. • 2-Faults: Mayform 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 Unconformity 17 Anticline 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. • 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.
- 18. • A relativelyimpermeable 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. 18 Gypsum Anhydrite
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