The conversion of organic matter to petroleum nanoxia coolforce

The conversion of organic matter to petroleum


Suez university

Faculty of petroleum mining engineering

The conversion of organic matter to petroleum


Belal farouk el-saied ibrahim

Class / III

Section / engineering geology and geophysics

The reference / pet. Geology


Presented to

Prof. Dr. / shouhdi E. Shalaby


Organic matter

When an organism (plant or animal)

Dies, it is normally oxidized under

Exceptional conditions: organic

Matter is buried and preserved in

Sediments the composition of the

Organic matter strongly influences

Whether the organic matter can

Produce coal, oil or gas.


Basic components of organic

Matter in sediments



• LIPIDS (fats)


All of these + time +

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Temperature + pressure =



Biomolecules in living organisms

Lipids, mostly fats, oils and waxes, have the greatest

Potential to be hydrocarbon sources. They are combinations

Of the fatty acids of the general formula cnh2no2 with

Glycerol, C3H5(OH)3. An important example is glyceride

C17H35COOCH3 formed from the stearic acid.

Proteins are giant molecules that make up the solid

Constituents of animal tissues and plant cells. They are rich

In carbon but contain substantial amounts of N, S and O.

Carbohydrates are based on sugars cn(H2O)n and their

Polymers (cellulose, starch, chitin). They are common in

Plant tissue.

Lignin is a polymer consisting of numerous aromatic rings. It

Is a major constituent in land plants and converts to coal

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Through desoxygenation.


Environment of the transformation

We have examined the type of raw material needed and

How it must accumulate in the natural environment. The

Next link in the process is to examine what happens to this

Organic matter (OM) when buried and subjected to

Increased temperature and pressure. One thing to

Remember is that not all of the organic carbon (OC) in

Sedimentary rocks is converted into petroleum

Hydrocarbons. A portion of the total organic carbon (TOC)

Consists of kerogen. We will look at the transformation of

OM first to kerogen, then to petroleum hydrocarbons.


The only elements essential to the transformation of organic matter (OM) into petroleum

Are hydrogen and carbon. Thus the nitrogen and oxygen contained in the OM must

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Somehow be removed while at the same time preserving the hydrogen-rich organic

Residue. The formation of petroleum at this point must occur in an oxygen-deficient

Environment, not be subjected to prolonged exposure to the atmosphere or to aerated

Surface or subsurface waters containing acids or bases, come into contact with elemental

Sulfur, vulcanicity, or other igneous activity, and have a short transportation time from the

Time of death to that of burial. All of these conditions must be met in order to avoid

Decomposition of the OM. All of this implies that as dead organic matter falls to the sea

Floor (organic rain), the hydrocarbon constituents needed for creating the end product will

Be preserved only if the water column through which they are falling is anoxic – lacking

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Living organisms, fall is rapid – the particle size must not entirely be microscopic, bottom

Dwelling predators are lacking, and there is a rapid sedimentation rate – rapid deposition

Buries the OM below the reach of mud-feeding scavengers.


Once the organic material is buried within the sea floor,

Transformation begins. It is a slow process that occurs to the OM. The

General process can be illustrated by the following formulas:

OM + transformation = kerogen + bitumen (by product)

Kerogen + bitumen + more transformation = petroleum

There are three phases in the transformation of OM into

Hydrocarbons: diagenesis, catagenesis, and metagenesis (tissot,

1997). Diagenesis occurs in the shallow subsurface and begins during

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Initial deposition and burial. It takes place at depths from shallow to

Perhaps as deep as 1,000 meters and at temperatures ranging from

Near normal to less than 60oc. Biogenic decay aided by bacteria (such

AsThiobacillus) and non-biogenic reactions are the principal processes

At work producing primarily CH4(methane), CO2 (carbon dioxide),

H2O (water), kerogen, a precursor to the creation of the petroleum,

And bitumen.


Temperature plays an important role in

The process. Ambient temperatures

Increase with depth of burial which

Decreases the role of bacteria in the

Biogenic reactions because they die out.

However, much of the initial methane

Production begins to decline because it is

The bacteria that produces the methane

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As a by-product during diagenesis.

Simultaneous to the death of the bacteria

However, the increased temperatures

Accelerate organic reactions.


The dependence of chemical reaction rates upon

Temperature is commonly expressed by:

Arrhenius equation


R =gas constant (0.008314 KJ/mol0k)

T=absolute temperature

E=activation energy

A=frequency factor


The catagenesis (meaning thermodynamic,

Nonbiogenic process) phase becomes

Dominant in the deeper subsurface as burial

(1,000 – 6,000 m), heating (60 – 175oc), and

Deposition continues. The transformation of

Kerogen into petroleum is brought about by a

Rate controlled, thermocatalytic process where

The dominant agents are temperature and



The temperatures are of non-biological origin; heat is

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Derived from the burial process and the geothermal

Gradient that exists within the earth’s crust. The

Catalysts are various surfactant materials in clays and

Sulfur. Above 200o C, the catagenesis process is

Destructive and all hydrocarbons are converted to

Methane and graphite. And at 300o C, hydrocarbon

Molecules become unstable. Thus thermal energy

(temperature) is a critical factor, but it is not the only

Factor the time factor is also critical because it provides

Stable conditions over long periods of time that allows

The kerogen sufficient cooking time – exposure time of

Kerogen to catagenesis. Thus the catagenesis phase

Involves the maturation of the kerogen; petroleum is

The first to be released from the kerogen followed by

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Gas, CO2 and H2O.


The third phase is referred to as metagensis. It

Occurs at very high temperatures and pressures

Which border on low grade metamorphism. The

Last hydrocarbons released from the kerogen is

Generally only methane. The H:C ratio declines

Until the residue remaining is comprised mostly

Of C (carbon) in the form of graphite.


Preservation of organic matter

The biomolecules described before are reduced forms

Of carbon and hydrogen. Their preservation potential

Depends crucially on anoxic conditions, i.E. The

Absence of oxygen that could oxidize them.

Stratified basins that prevent vertical circulation and

Thus the transport of oxygen to greater depths

Provide excellent conditions for this.Nanoxia coolforce an example is the

Black sea, which is salinity-stratified, but many lakes

Are also anoxic in their deeper waters because of

Thermal stratification or abundance of nutrients and

Lack of circulation.


Preservation of organic matter

Access to air (oxygen) rapidly – at geological scales – oxidizes

Organic matter and converts it into CO2 and H2O.

The total carbon content in the earth’s crust is 9·1019 kg (the

Hydroand biosphere contain less than 10-5 of this). Over 80%

Of this is in carbonates. Organic carbon amounts to 1.2·1019

Kg and is distributed approximately as follows:

Dispersed in sedimentary rocks (~) 97.0 %

Petroleum in non-reservoir rocks 2.0 %

Coal and peat 0.13 %

Petroleum in reservoirs 0.01 %

This illustrates the low efficiency of the preservation process.Nanoxia coolforce


Total organic carbon (TOC)

If a rock contains significant amounts of organic carbon, it is

A possible source rock for petroleum or gas. The TOC content

Is a measure of the source rock potential and is measured

With total pyrolysis.

The table below shows how TOC (in weight percent) relates

To the source rock quality.

TOC quality

0.0-0.5 poor

0.5-1.0 fair

1.0-2.0 good

2.0-4.0 very good

4.0 excellent


TOC types

TOC in sedimentary rocks can be divided into two types:

• bitumen, the fraction that is soluble in organic solvents such

As chloroform

• kerogen, (κεροσ = wax) the insoluble, nonextractable

Residue that forms in the transformation from OM kerogen is an

Intermediate product formed during diagenesis and is the

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Principal source of hydrocarbon generation. It is a complex

Mixture of high-weight organic molecules with the general

Composition of (C12H12ON0.16)x


Conversion of OM to HC

The principal condition is that this conversion take place in an

Essentially oxygen-free environment from the very beginning of

The process. Anaerobic bacteria may help extract sulfur to form

H2S and N, in addition to the earlier formation of CO2 and H2O.

This explains the low sulfate content of many formation waters.

On burial, kerogen is first formed. This is then gradually cracked

To form smaller HC, with formation of CO2 and H2O. At higher

Temperatures, methane is formed and hcs from C13 to C30.

Consequently, the carbon content of kerogen increases with

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Increasing temperatures. Simultaneously, fluid products high in

Hydrogen are formed and oxygen is eliminated.


Dehydrogenization and carbonization

The dehydrogenation and carbonization of organic

Source n be illustrated with the H:C ratio during the

Formation of coals:

Source material H:C ratio

Wood 1.5

Peat 1.3

Lignite 1.0

Bit. Coal 0.8

Anthracite 0.3-0.0

Average, in weight %


Deoxygenization and carbonization

The deoxygenation and carbonization of the

Source material is illustrated with the

Formation of petroleum:

Source material O:C ratio

Organisms 0.35-0.6

Pyrobitumen (kerogen) 0.1-0.2

Petroleum (average) 0.004

Average, in weight %


Source rock quality

The primary factor determining source rock

Quality is the level of TOC.Nanoxia coolforce

Additionally, the quality of the source rock is

Better for higher H:C ratios before thermal


As thermal maturation proceeds and hcs are

Formed, the kerogen will continuously

Deteriorate as a source for HC formation.



Kerogen (algae)

Lipid-rich kerogen

(phyto- and


Humic kerogen

(land plants)

“van krevelen diagram” TAI, VR: maturation indicators


Transformations with depth

Source: north, F.K. (1985) petroleum geology, allen unwin

LOM = level of organic metamorphism; BTU = british

Thermal unit; VM = volatile matter


Rate of maturation

Source: north, F.K. (1985) petroleum geology, allen unwin

Temperature is the single most important factor in thermal maturation.


Rate of maturation ctd.Nanoxia coolforce

Source: north, F.K. (1985) petroleum geology, allen unwin

Time is the second most important factor in thermal maturation


Purposes of maturation indicators

• to recognize and evaluate potential source rocks for oil and

Gas by measuring their contents in organic carbon and their

Thermal maturities

• to correlate oil types with probable source beds through their

Geochemical characteristics and the optical properties of

Kerogen in the source beds

• to determine the time of hydrocarbon generation, migration

And accumulation

• to estimate the volumes of hydrocarbons generated and thus

To assess possible reserves and losses of hydrocarbons in the



Lopatin’s TTI index

V. Lopatin (1971) recognized the

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Dependence of thermal maturation

From temperature and time. He

Developed a method where in the

Temperatures are weighted with the

Residence time the rock spent at this

Temperature. Periods of erosion and

Uplift are also taken into account. This

So-called time-temperature index TTI

Is still in use, although in variations.

The plot on the right shows a simple

Depiction of it. Rock of age A enters the

Oil-generating window at time y, while

The older rock B has been at that time

Already in the gas-generating window

And will stay there until the present.

Source: north, F.K. (1985) petroleum geology, allen unwin


Other maturation indicators

Several approaches to quantify the degree of maturation have been

Proposed aside from the TTI.Nanoxia coolforce most of them are sensitive to

Temperature and time.

• vitrinite reflectance (ro) measures the reflectance of vitrinite (see

Kerogen maturation diagram) in oil, expressed as a percentage. It

Correlates with fixed carbon and ranges between 0.5 and 1.3 for the

Oil window. Laborious but widely used.

• thermal alteration index (TAI) measures the color of finely

Dispersed organic matter on a scale from 1 (pale yellow) to 5

(black). This index has a poor sensitivity within the oil window (TAI

Around 2.5 to 3.0) and is not generally used.

• level of organic maturation (LOM) is based on coal ranks and is

Adjusted to give a linear scale.


Correlation of TTI, ro, and TAI


The oil and gas windows

The oil and gas windows

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A similar slide as before. It

Shows clearly at what

Temperatures oil generation


Gas generation diminishes

Above ~180°C

Source: north, F.K. (1985) petroleum geology,

Allen unwin


Oil source rock criteria

The criteria for a sedimentary rock to be an effective oil source

Can be quantitatively described. They are as follows:

• the TOC should be 0.4% or more

• elemental C should be between 75% and 90% (in weight)

• the ratio of bitumen to TOC should exceed 0.05

• the kerogen type should be I or II (from lipids)

• vitrinite reflectance should be between 0.6 and 1.3%


Summary: origin and maturation

This diagram shows the

Development of biomolecules

Into petroleum and, with

Further maturation, into gas

(left branch at bottom) which

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Causes the residues to

Become increasingly more

Carbon-rich (right branch at


Source: hunt, J.M. (1995) petroleum geochemistry and

Geology, 2nd edition. W.H. Freeman co