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ORIGIN OF PETROLEUM.pptx
- 1. Origin of petroleum andNatural gas
- 2. ORIGIN OF PETROLEUM Tobe considered are these 3 stages: •Formation of Petroleum •Migration of Petroleum •Accumulation of Petroleum
- 3. Formation of Petroleum •There are 2 theories concerning the formation of petroleum: • The Inorganic theory • The Organic theory
- 4. Inorganic Theory • Berthelot(1860) & Dmitri Mendeleev (1902): • Iron carbide in the earth’s mantle would react with percolating water to form methane. • FeC2+ 2H2O →CH4+ FeO2 • This theory is called Deep-Seated Terrestrial Hypothesis.
- 5. • Sokoloff (1890): •Hydrocarbons precipitated as rain from the original nebular matter from which solar system was formed. • The hydrocarbons were the ejected from earth’s interior onto surface rocks. • This theory is called Extraterrestrial Hypothesis
- 6. Problems with InorganicTheories : • No field evidence that inorganic processes have occurred in nature. • Commercial accumulations are restricted to mainly sedimentary basins. • Accumulations are absent from igneous and metamorphic rocks.
- 7. Organic Theory • Earlymarine life forms living on earth were primarily plankton (rich in hydrogen & carbon) • Over 95% of living matter in the ocean is plankton.
- 8. • As theseplankton died, their remains were captured by the process of erosion and sedimentation.
- 9. • Successive layersof organic-rich mud & silt covered preceding layers of organic-rich sediments & overtime created layers on the sea floor rich in the fossil remains of previous life.
- 10. • Thermal maturationprocesses (decay, heat, pressure) slowly converted the organic matter into oil & gas over periods of millions of geologic years. • Conversion of the organic material is called Catagenesis. • It usually occurs under anaerobic conditions.
- 11. • Clay &silt are carried together with the dead organic remains & deposited under deltaic, lacustrine & marine conditions to form Source rocks. • Black-coloured, organically-rich shales deposited in a non-oxidizing, quiet marine environment are considered the best source rocks.
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- 13. • Shale rock= 99% clay mineral + 1% organic material. • Kerogen Insoluble High molecular weight Polymeric compound
- 14. • Thermal alterationof kerogen forms crude oil by increasing the carbon contents. • At shallow depths (< 3,000 ft), bacteria actions on organic materials form Biogenic Gas(natural gas). • At great depths (high temperature & overburden), Thermogenic Gas is formed. • Later stages of thermogenesis will form wet gas and condensate.
- 15. Supports for organichypothesis • Carbon & hydrogen are the primary constituents of organic material, both plant & animal. • Nitrogen & Porphyrins are found in organic matter & in many petroleum. • Porphyrins are chlorophyll derivatives in plants & blood derivatives in animals.
- 16. Migration of Petroleum •Produced hydrocarbons migrates upward from the deeper, hotter parts of the basin through permeable strata into suitable structures. • There are 2 stages of migration: • Primary Migration –Kerogen transformation causes micro-fracturing of the impermeable & low porosity source rock, allowing hydrocarbons to move into more permeable strata.
- 17. Secondary Migration • Thegenerated fluids move more freely along bedding planes and faults into a suitable reservoir structure. • Migration can occur over several tens of kilometers in lateral directions.
- 18. Accumulation of Petroleum •Accumulation & storage occur when the migrating fluids encounter an impermeable shale or dense layer of rock. • This is called a Trap. • After accumulation, the fluids tend to stratify according to their relative densities: • Gas • Oil • Water
- 20. • If themigrating fluids do not encounter a trap, they tend to flow to the surface or deposited on the ocean floor. • Examples are: • Seepages • Escaping natural gas • Bituminous lakes
- 22. • Reservoirs arecomposed of either: • Clastic formation –sandstone reservoirs made from silicates (quartz, SiO2). • Carbonate formation –carbonate reservoirs made from detritus(coral or shell fragments). • Reservoirs must be: • Porous • Permeable • Trapped.
- 23. Anticlinal traps • Ananticline is a structural trap formed by the folding of rock strata into an arch-like shape. • The rock layers in an anticlinal trap were originally laid down horizontally and then earth movement caused it to fold into an arch- like shape called an anticline.
- 25. fault trap • Thistrap is formed by the movement of permeable and impermeable layers of rock along a fault plane. • In some cases, there can be an impermeable substance smeared along the fault surface (such as clay) that also acts to prevent migration. This is known as clay smear.
- 27. Stratigraphic traps • Stratigraphictraps are formed as a result of lateral and vertical variations in the thickness, texture, porosity or lithology of the reservoir rock. • Examples of this type of trap are an unconformity trap, a lens trap and a reef trap.
- 29. A salt dometrap • A salt dome trap is an area where oil has been trapped underground by salt pushing upward. • A salt dome trap is where a mass of salt from deep in the Earth's crust is pushed upward forming oil traps in a rock layer containing oil. • Salt dome traps form where bodies of salt flow upward and pierce overlying rock layers.
- 31. combination traps • Trapswith two or more trapping elements are called combination traps
- 32. What is naturalgas? • Natural gas is a fossil energy source that formed deep beneath the earth's surface. Natural gas contains many different compounds. • The largest component of natural gas is methane, a compound with one carbon atom and four hydrogen atoms (CH4). • Natural gas also contains smaller amounts of natural gas liquids (NGL, which are also hydrocarbon gas liquids), and nonhydrocarbon gases, such as carbon dioxide and water vapor. • We use natural gas as a fuel and to make materials and chemicals.
- 33. How did naturalgas form? • Millions to hundreds of millions of years ago and over long periods of time, the remains of plants and animals (such as diatoms) built up in thick layers on the earth’s surface and ocean floors, sometimes mixed with sand, silt, and calcium carbonate. • Over time, these layers were buried under sand, silt, and rock. • Pressure and heat changed some of this carbon and hydrogen-rich material into coal, some into oil (petroleum), and some into natural gas.
- 35. Where is naturalgas found? • In some places, natural gas moved into large cracks and spaces between layers of overlying rock. The natural gas found in these types of formations is sometimes called conventional natural gas. • In other places, natural gas occurs in the tiny pores (spaces) within some formations of shale, sandstone, and other types of sedimentary rock. • This natural gas is referred to as shale gas or tight gas, and it is sometimes called unconventional natural gas. • Natural gas also occurs with deposits of crude oil, and this natural gas is called associated natural gas. • Natural gas deposits are found on land, and some are offshore and deep under the ocean floor. • A type of natural gas found in coal deposits is called coalbed methane.