Ku Geology 3

PET—631Generation of Hydrocarbon

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon The Story of Oil in Pennsylvania • The most important oil well ever drilled was in the middle of quiet farm country in northwestern Pennsylvania in 1859. • This was one of the first successful oil wells that was drilled for the sole purpose of finding oil. • Known as the Drake Well, after "Colonel" Edwin Drake, the man responsible for the well, it began an international search for petroleum, and in many ways eventually changed the way we live.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Oil Hydrocarbon PET—631 Origin of and Gas Organic (bionic) or Inorganic (abionic)Theory. • •

There are two theories of origin: Organic (bionic) or Inorganic (abionic).

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Inorganic Early theories postulated an inorganic origin when it became apparent that there were widespread deposits of petroleum throughout the world.

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Dmitri Mendele'ev (1877), a Russian and the father of the periodic table of elements, reasoned that metallic carbides deep within Earth reacted with water at high temperatures to form acetylene (C2H2) which subsequently condensed to form heavier hydrocarbons.

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This reaction is readily reproduced in the laboratory.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Inorganic Theory Continue • Berthelot, 1860 and Mendele'ev, 1902 theorized that the mantle contained iron carbide which would react with percolating water to form methane:

FeC2 + 2H2O = CH4 + FeO2 • The problem was and still is the lack of evidence for the existence of iron carbide in the mantle. • These theories are referred to as the deep-seated terrestrial hypothesis. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Inorganic Theory Continue • Another inorganic hypothesis was suggested by Sokoloff (1890) who proposed a cosmic origin. His theory was such as hydrocarbons precipitated as rain from original nebular matter from which the solar system was formed and then ejected from earth's interior onto surface rocks. • This theory and others like it are referred to as the extraterrestrial hypothesis

Department of Petroleum Technology, University of Karachi

PET—631Generation Hydrocarbon PET—631 Origin ofofOil and Gas Questions against Inorganic Origin • Commercial accumulations are restricted to sedimentary basins, •

• petroleum seeps and accumulations are absent from igneous and metamorphic rocks, and • gas chromatography can fingerprint the organic matter in shales that found in the adjacent pool. • Thus current theory holds that most petroleum is formed by the thermal maturation of organic matter. • An Organic Origin generated the vast reserves (pools) of oil and gas. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

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Organic Hypothesis - Summary

• The organic theory became the accepted theory about the turn of the century as the oil and gas industry began to fully develop and geologists were exploring for new deposits. • Simply stated, the organic theory holds that the carbon and hydrogen necessary for the formation of oil and gas were derived from early marine life forms living on the Earth during the geologic past -- primarily marine plankton.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Organic Hypothesis: • There are a number of compelling reasons that support an organic development hypothesis. • First and foremost, is the • carbon-hydrogen-organic matter connection. • Carbon and Hydrogen are the primary constituents of organic material, both plant and animal. • Moreover, carbon, hydrogen, and hydrocarbons are continually produced by the life processes of plants and animals. Department of Petroleum Technology, University of Karachi

PET—631Generation PET—631 Origin ofof OilHydrocarbon and Gas • Second were observations dealing with the chemical characteristics of petroleum reservoirs. • Nitrogen and porphyrins (chlorophyll derivatives in plants, blood derivatives in animals) are found in all organic matter; they are also found in many petroleum. • Presence of porphyrins also mean that anaerobic conditions must have developed early in the formation process because porphyrins are easily and rapidly oxidized and decompose under aerobic conditions. • Additionally, low Oxygen content also implies a reducing environment. • Thus there is a high probability that petroleum originates within an anaerobic and reducing environment. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Third were observations dealing with the physical characteristics. •

Nearly all petroleum occurs in sediments that are primarily of marine origin.

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Petroleum contained in non-marine sediments probably migrated into these areas from marine source materials located nearby.

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Furthermore, temperatures in the deeper petroleum reservoirs seldom exceed 300oF (141oC) .

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But temperatures never exceeded 392oF (200oC) where porphyrins are present because they are destroyed above this temperature.

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Therefore the origin of petroleum is most likely a low-temperature phenomenon.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon PREREQUISITES FOR HYDROCARBON ACCUMULATION •

• • • • • • •

The accumulation of hydrocarbons and formation of oil or gas deposit involve certain prerequisites. These are the following: 1. Source Rock 2. Reservoir Rock 3. Trap 4. Seal 5. Timing 6. Migration

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon HYDROCARBON SYSTEM Step 1 Energy Capture Step 2 - Source Sediments Step 3- Sediment Maturation Step 4 - Reservoir Rock Step 5 - Traps Step 6 - Seal/Trap Rock

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Energy Capture • •

• • • • • • • • • • • •

Diatoms float in the top few meters of the oceans and also happen to be a major source of food for many forms of ocean swimmers. Their skeletons are chemically very similar to sand - in fact, they are made of the same material (silica). Diatoms produce a kind of oil by themselves – both to store chemical energy from photosynthesis and to increase their ability to float. But this small amount of oil still needs to become concentrated and mature before it can be taken from the ground and used as fuel oil.

DEPARTMENT OF of PETROLEUM TECHNOLOGY Department Petroleum Technology,

UNIVERSITYof OF Karachi KARACHI University

PET—631Generation of Hydrocarbon Energy Capture •

There are more than 200 genera of living diatoms, and it is estimated that there are approximately 100,000 extant species.

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Diatoms are a widespread group and can be found in the oceans, in freshwater, in soils and on damp surfaces.

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Most live pelagically in open water, although some live as surface films at the water-sediment interface (benthic), or even under damp atmospheric conditions.

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They are especially important in oceans, where they are estimated to contribute up to 45% of the total oceanic primary production.

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Although usually microscopic, some species of diatoms can reach up to 2 millimetres in length.

DEPARTMENT OF of PETROLEUM TECHNOLOGY UNIVERSITYof OF Karachi KARACHI Department Petroleum Technology, University

PET—631Generation of Hydrocarbon Source Sediments •

Since almost all oil comes from rocks that were formed underwater, floating ocean life (tiny, tiny creatures known as diatoms, foraminifera, and radiolarians –

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all just as small as a grain of sand) that settle to the bottom of the sea is what eventually turns into oil.

• • •

How could something so small give us so much oil? Well, it takes many thousands of years (and millions of millions dead critters) to form thick deposits of organic-rich sludge at the bottom of the ocean.

DEPARTMENT OF of PETROLEUM TECHNOLOGY UNIVERSITYof OF Karachi KARACHI Department Petroleum Technology, University

PET—631Generation of Hydrocarbon Step 1 - Energy Capture

• In fact, most scientists agree that oil comes from creatures the size of a pinhead. • These one-celled creatures, known as diatoms, aren't really plants, but share one very important characteristic with them – • they take light from the sun and convert it into energy. ( PHOTSYNTHESIS ) –Side view of a typical diatom, the energy-trapping organism generally thought to be the origin of oil. DEPARTMENT OF of PETROLEUM TECHNOLOGY UNIVERSITYof OF Karachi KARACHI Department Petroleum Technology, University

PET—631Generation of Hydrocarbon PET—631 Photosynthesis • Photosynthesis is a process of taking inroganic material to make new organic matter through the combining of carbon dioxide and water using solar energy. • This process only occurs in green plants, blue-green algae, and certain bacteria.

DEPARTMENT OF of PETROLEUM TECHNOLOGY Department Petroleum Technology,

UNIVERSITYof OF Karachi KARACHI University

PET—631Generation of Hydrocarbon How does photosynthesis occur? Water is taken in through the roots of the plant and transported to the leaves by the xylem (tubes that carry water) in the stems. •

Carbon dioxide animals breathe out from the air goes into the leaves through the tiny pores called stomata and is spreads to the cells that contain chlorophyll in the inside layer of the leaf.

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Sunlight is used to break down the water in the plant into oxygen, which the plant gives off and we use to breathe.

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The hydrogen is then used with the carbon dioxide to create the food for the plants and ultimately food for animals as well.

DEPARTMENT OF of PETROLEUM TECHNOLOGY UNIVERSITYof OF Karachi KARACHI Department Petroleum Technology, University

PET—631Generation of Hydrocarbon Photosynthesis

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Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Aerobic and Anaerobic Condition • • • • • • •

Aerobic Oxygen No odor Clear water Fish thrive Sludge degrades Controlled algae growth

• • • • • • •

Anaerobic No oxygen Odors arise Water turns black Fish die Sludge builds-up Uncontrolled algae growth

Department of Petroleum Technology, University of Karachi

PET—631Generation PET—631 Origin ofof OilHydrocarbon and Gas

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•

Anaerobic conditions are synonymous with dead or dying conditions. Dead water cannot support diverse animal or plant life, and septic conditions arise creating toxic gases and solutions from decaying organic matter. As water becomes anaerobic it more readily dissolves precipitates such as Phosphorous providing an increase of nutrients in solution.

Department of Petroleum Technology, University of Karachi

PET—631 Origin ofof OilHydrocarbon and Gas PET—631Generation

•

• •

This increase in nutrients promotes the growth of algae and weeds which in turn die off and further contribute to sludge build-up. Anaerobic conditions facilitate an endless cycle of propagation and accumulation of organic matter without any beneficial degradation. The sludge layer continually increases producing black and smelly waters.

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Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Formation ofliquid, Hydrocarbon All fossil fuels, whether solid, or gas, are the result of organic material being covered by successive layers of sediment over the course of millions of years. Some deposits of coal can be found during the time of the dinosaurs. For example, thin carbon layers can be found during the late Cretaceous Period (65 million years ago) - the time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the Carboniferous Period. Fossil fuels supply over 80% of the world’s energy needs. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Marine Ecosystems: • Simple photosynthesizing Algae are the primary organic carbon producers in the world’s oceans, are the start of a complex food chain.

• Phytoplanktons are responsible for over 90%

supply of OM (organic Matter) in the world’s ocean.

of

• The Phytoplankton group includes the “Diatoms”,

Dinoflagellates”, “Blue-Green Algae” and “Nannoplankton”.

• According to Romankevich(1984), only a small percentage (o.4%) out of 26.6 x 10 tons/year of OC (organic carbon) in the world’s seas and oceans is transferred to and preserved in sea bottom sediment. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Marine Ecosystems • Apart from phytoplankton, other organisms such as “ Zooplankton” , “Benthos organism” , “Bacteria” , and “Fish “ may also be important elements of the biomass. • The main function of the bacteria is to break down dead (OM) organic matter, but the bacteria may themselves also contribute to the organic content of the sediment. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Geographical Variation in Phytoplankton • The open ocean accounts for a large percentage of the OC (Organic Carbon) produced; the concentration of OC/m in open ocean water is relatively low. • In contrast, the continental shelves are very rich, particularly in some specific environments of enhanced organic activity such as the Algally-dominated inter-tidal zone and in Reefs and Estuaries. • Upwelling Zones are also areas of relatively high organic productivity.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Sediment Maturation •

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It is believed that high heat & intense pressure help along various chemical reactions, transforming the soft parts of ancient organisms found in the deep-sea sludge into oil &natural gas. At this point, this ooze at the bottom of the ocean turns into source rock.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon HOW OIL AND GAS ARE CREATED

• Crude is associated mainly with sedimentary rocks deposited in the marine environment. • These deposits indicate that high productivity of organic carbon is important and contain many fossil microorganisms like diatoms and radiolarians. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Organic-rich mud and silt •

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Successive layers of organic-rich mud and silt covered preceding layers of organic rich sediments and over time created layers on the sea floor rich in the fossil remains of previous life (Fig. 3). Thermal maturation processes (decay, heat, pressure) slowly converted the organic matter into oil and gas.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Thermal maturation processes • Add additional geologic time (millions of years) and the organic rich sediments were converted into layers of rocks. • Add more geologic time and the layers were deformed, buckled, broken, and uplifted; the liquid petroleum flowed upward through porous rock until it became trapped and could flow no further forming the oil and gas that we explore for at present (Fig. 4).

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Marine and Lacustrine Environment

Anoxic bottom waters are required for organic rich sediments to be preserved Otherwise the organic matter just feeds other critters, or bacteria.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Trends in organic productivity: • Primary productivity decreases from coastal/marine shelf into open ocean. • Mid-Latitude humid and equatorial latitudes are more productive than tropical latitudes. • Lowest productivity is in polar and arid tropical areas. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

Organic matter

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon High productivity

Plate tectonics creates areas that are ideal for oil accumulation. High productivity, especially along continental coasts, is ideal. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Kind of Organic matter • Lipids are organic molecules • Lignin that are insoluble in water and other polar solvents.

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Lipids are readily soluble in nonpolar solvents, such as chloroform, benzene, and ether.

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• Lipids include fats and oils

(important as energy storage compounds), phospholipids and glycolipids (part of the structure of cell membranes), waxes (protective surface coatings on many plants and animals), and steroids (found in some cell membranes and many hormones).

is one of the main constituents of the cell walls of woody plants and a large contributor to soil or-ganic matter.

• Lignin is generally believed to be relatively resistant against microbial decomposition and that lignin residues contribute significantly to the large stock of old, only slowly de-gradable organic matter in the soil

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Origin of Source Rocks Requirements for High Organic Productivity • • • • •

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Organic Matter

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• Proteins • Carbohydrates (sugars, starch, cellulose) • Lipids (oils, fats) More resistant to decay • Lignin (in plants) More resistant to decay • HC generation is limited by available H (reducing environment)

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• Light (for photosynthesis) • Temperature • Nutrients • Low turbidity • Phytoplankton (Photosynthesizing algae) 90% of Organic Matter in Oceans • Bacteria, zooplankton, fish, etc

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How Good Source Rocks Form:

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Areas of High Productivity

• 1. Sedimentation in areas of high

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• At boundaries between polar and

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temperate regions • West side of continents • In the upper 100m

organic productivity • 2. Preservation of organic matter in sediment

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon The factors controlling organic productivity

• Sunlight: • The zone of highest productivity is the top 200 meters of the world’s seas, especially the upper 60-8meters. This zone is also called Photic zone. • Nutrient Supply: • Nutrients, particularly “Nitrates” and “Phosphates, are required to sustain high organic productivity. These are supply by water circulation. • Stagnant seas are not very productive. • Nutrient supply is also locally increased in areas of large river input and coastal abrasion. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon The factors controlling organic productivity • Turbidity: • The state, condition, or quality of opaqueness or reduced clarity of a fluid, due to the presence of suspended matter. • Productivity is limited in areas with turbid coastal waters. • Salinity: • The total quantity of dissolved salts in sea water, measured by weight in parts per thousand, with the following qualifications: • All the carbonates has been converted to oxide, all the bromide and iodide to chloride, and all the organic matter has been completely oxidized. • Extremes of salinity (high or low) reduce the diversity of species present, though the productivity of certain groups may still be very high. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon The factors controlling organic productivity • Temperature: • Temperature also influences the composition of the phytoplankton population, rather than net productivity. • Dinoflagelates, require high water temperatures of > 25 C*. • Diatoms and Radiolarians prefer 5-15C*. • Note: • The critical factors for source bed development are the deposition and preservation of (OM) organic matter in significant quantities in sediments, rather than productivity. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Dead Organism

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Maturation of organic matter

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Kind of Organic matter Carbohydrates are the main energy-storage molecules in most organisms. They are also important structural components for many organisms. The building blocks of carbohydrates are small molecules called sugars, composed of carbon, hydrogen and oxygen. Carbohydrates are classified according to the number of sugar molecules they contain, such as glucose, fructose, ribose, and galactose,

Proteins are complex, specialized molecules composed of carbon, hydrogen, oxygen, and nitrogen. Many proteins also contain sulfur. The building blocks of proteins are the amino acids. There are twenty different amino acids commonly found in proteins. All of these amino acids have a similar structure.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

Sedimentation Rate As the rate of the sedimentation increases, the TOC (Total Organic Carbon) content of the sedimentation also increases because the sediment passes more rapidly through the near-surface zone in which the intense microbial degradation of the OM (Organic Matter) would take place.

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Comparison of effects of sedimentation rates on the preservation and maturation of organic matter Zone Rate of Sedimentation Prospect Aerobic Zone

Very Slow Sedimentation All organic destroyed

Zero

Sulfate Reduction

Slow sedimentation Massive modification Poor Sulfides and Carbonates Fermentation Zone Intermediate rates Significant modification Fair of organic matter Carbonates Thermal Saturation Fairly Rapid Sedimentation organic matter little Good Zone affected by Aerobic and sulfate reduction zone Liquid Hydrocarbon Very rapid Sedimentation Liquid Hydrocarbon Window may be destroyed Uncertain

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Sediment Maturation • In petroleum geology, the maturity of a rock is a measure of its state in terms of hydrocarbon generation. • Maturity is established using a combination of geochemical and basin modelling techniques. • Organic-rich rocks (termed source rocks) will alter under increasing temperature such that the organic molecules slowly mature into hydrocarbons (see diagenesis).

• . Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Sediment Maturation • Source rocks are therefore broadly categorised as • immature (no hydrocarbon generation), • sub-mature (limited hydrocarbon generation), • mature

(extensive hydrocarbon generation)

• overmature (most hydrocarbons have been generated). • The maturity of a source rock can also be used as an indicator of its hydrocarbon potential. • That is, if a rock is sub-mature, then it has a much higher potential to generate further hydrocarbons than one that is overmature. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Crude oil, tar, and natural gas Composition • Element

crude % weigh

• Carbon

82.2-87.1

• Hydrogen 11.7-14.7

tar(asphalt)

natural gas

80-85

65-80

8.5-11

1-25

• sulfur.

1-5.5

2-8

trace-.2

• nitrogen.

1-1.5

0-2

1-15

• oxygen.

1-4.5

-

-

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Conversion of organic Matter • Low-temperature chemical and biological reactions (called digenesis) that occur during transport to and early burial in the depositional environment modify this organic matter. • Many of the chemical compounds present in sediments are in fact derived from bacteria, and were formed as dead organic matter was converted to microbial tissues. • Most of this organic matter is transformed during digenesis info very large molecules, the largest of which are called kerogen. Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Transformation of organic matter • Heat combined with increased pressure aids the transformation of organic matter into petroleum products. • But too much heat or too much pressure can prevent any oil from forming. • Many geologists use petroleum formation to guide them on how much heat was in an area. • For example, if oil is found, the temperature never exceeded 200E C or (392E F). Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Carbon Cycle

PET—631Generation of Hydrocarbon Fate of Organic Matter in Oceans

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Conversion of Organic matter

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Kerogene Classification

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Kinds of Kerogene

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Type of Kerogene

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Formation of Hydrocarbon •

Formation of Hydrocarbons and Hydrocarbon Reservoirs/Traps.

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Diagenesis.

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Biogenic decomposition produces biogenic methane. At slightly higher temperatures and pressures the organic matter is converted to kerogen - an amorphous material of carbon, hydrogen, and oxygen.

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Catagenesis.

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At higher temperatures and pressures kerogen is altered and the majority of crude oil is formed. During this phase and the next, the larger molecules break down into simpler molecules (a process called cracking).

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Metagenesis.

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In the final stage of alteration (at higher temperatures and pressures) of kerogen and crude oil, natural gas (mostly methane) is produced and residual carbon is left in the source rock

Department of Petroleum Technology, University of Karachi

PET—631Generation of Hydrocarbon Figure 1. Diagrammatic illustration of kerogen composition, which leads to oil and gas formation directly from kerogen cracking and gas from oil cracking.

Department of Petroleum Technology, University of Karachi