Origin of oil and gas

TÌM HIỂU VỀ MGIOONG GỐC CỦA DẦU MỎ VÀ KHÍ ĐỐT DUNG CHO BỘ MÔN HÓA HỌC DẦU MỎ CÁC PHUONG TRÌNH LIÊN QUAN ĐẾN QUAS TRÌNH TẠO RA VÀ HÌNH THÀNH DẦU MỎ KHÍ ĐỐT

VIETNAM NATIONAL OF UNIVERSITY HANOI

HANOI UNIVERSITY OF SCIENCES

FACULTY OF CHEMISTRY

ASSIGNMENT ON:

PETROLEUM CHEMISTRY

ORIGIN OF OIL AND GAS

Lecturers: Assoc.Prof.Dr Do Van Dang Student: Dinh Thu Tra

Student code: 21001747

Hanoi-2024

ORIGIN OF OIL AND GAS Researching the origin of oil and gas faces many difficulties, because we cannot directly observe the formation of oil and gas On the other hand, due to the special state of oil and gas, when When thermodynamic conditions change, oil and gas also change in both physical properties and chemical composition and form new products that are completely different from the original material, making it difficult to determine its nature of starting material

Research on the origin of oil and gas is conducted experimentally in the laboratory, which includes preparing oil and oil products and studying geology in the field, geological structure of oil reservoirs, and chemical mechanisms of oil and gas organic matter transformation processes

in modern sediments, from which we can build hypotheses about the mechanism of oil formation

To solve the problem of the origin of petroleum, one of the most important issues is to explain the nature of the original material that creates petroleum, whether it is organic or inorganic Therefore, inorganic and organic schools were formed

I HYPOTHESIS OF INORGANIC ORIGIN (MINERAL ORIGIN)

1 Carbide hypothesis

Mendeleev proposed this hypothesis on the basis of chemical experiments According to him, the earth's core consists of molten metal (mainly iron), containing metal carbides, such as aluminum carbide (Al4C3), calcium carbide (CaC2)

Inside the earth, when water is applied, the following reaction occurs:

3FemCn + 4mH2O → mFe3O4 + C3nH8m Mendeleev hypothesized that the water participating in the above reaction seeped down from the surface along deep faults and tectonic cracks Hydrogen carbides are formed in a gaseous state and, under the influence of high pressure, will follow cracks to the upper regions of the Earth There they condense and concentrate in rocks to form oil fields

However, the above hypothesis does not convince geologists because of the following points: -Material inside the earth is in a plastic state, which eliminates cracks, a required condition of this hypothesis

-If there are cracks in the earth, water cannot penetrate because the temperature is too high Another hypothesis similar to the above hypothesis is that the earth's interior contains metal carbides such as Al4C3, CaC2 These substances are decomposed by water to produce CH4 and C2H2:

Al4C3 + 12H2O → 4Al(OH)3 + 3CH4 CaC2 + 2H2O → Ca(OH)2 + C2H2 The above hypothesis is supported by the following experiments In 1866, Berthelot synthesized aromatic hydrocarbons from acetylene at high temperature with catalysts In 1901,

Sabatier and Sendereus performed the hydrogenation reaction of acetylene on nickel and iron catalysts at temperatures ranging from 200 to 300oC, obtaining a series of hydrocarbons corresponding to the composition of oil Along with a series of experiments like the above, the hypothesis of the inorganic origin of oil has been accepted for quite a long time

However, the above hypothesis is also doubted by the following points:

Using modern methods, people have analyzed that petroleum contains porphyrins of plant and animal origin

In the earth's crust, the content of metal carbides is negligible

Hydrocarbons are often found in sedimentary layers, where the temperature rarely exceeds

150 ÷ 200oC (because the pressure is very high), so the temperature necessary for the synthesis reaction to occur is not enough

2 Hypothesis of magma origin

Under conditions of high temperature and pressure, carbon is released from its compounds in the magma solution In addition to free carbon, free hydrogen also exists in the magma solution Hydrocarbons are formed by the combination of hydrogen and carbon Initially it can be CH4, then polymerization can create CnHm compounds Depending on the values of n and m, these compounds can create gas (small n) or liquid (large n)

II THE HYPOTHESIS OF ORGANIC ORIGIN

1 Theoretical basis

a Biogeochemical basis

The chemical composition of oil and gas includes two elements typical of organic matter: carbon and hydrogen In addition, the composition of petroleum also includes oxygen, nitrogen, sulfur and phosphorus, which are the basic elements that create living matter as well as flammable minerals

- Isotope composition:

The S32/S34 isotopic composition in petroleum in different geological periods varies similarly to the variation in this ratio in sulfates of the same age

The C12/C14 isotope ratio in petroleum and in organic matter is similar

- Composition of hydrocarbides:

There is a similarity in the architecture of the range of organic compounds found in sedimentary rocks with the hydrocarbons that make up the petroleum mass

The presence of paraffin proves that the oil must be formed at temperatures below 200oC (decomposition temperature of paraffin)

Combinations of O, S, N compounds of organic origin are formed by decomposing organic matter

Rare elements in petroleum ash and coal have general distribution rules.

Optical activity is one of the most important evidences of the organic origin theory of petroleum The optical activity in petroleum is due to cholesterol - an organic compound of plant origin Synthetic oils are not optically active

Through laboratory experiments, it is possible to transform organic matter in the direction of creating oil

b Geological basis

-The majority (99.9%) of oil and gas fields are located in sedimentary rocks

-The formation of oil and gas fields is closely related to the neo-tectonic movement regime of the sedimentary basin as well as paleogeographic conditions

-In many oil and gas reservoirs, oil-bearing sandstone lenses have been discovered between impermeable rock layers

-In modern sediments, the transformation of organic materials in the direction of oil formation

is observed and their content increases with depth

2 Theory of organic origin of petroleum

This is the hypothesis about the formation of oil and gas from initial organic materials Those materials are the remains of marine or terrestrial plants and animals but are washed out to sea by rivers over a long period of time (millions of people) years) are deposited on the seabed

In seawater, there are many types of aerobic and anaerobic organisms, so when plants and animals die they are immediately decomposed (like albumin, carbohydrates) Bacteria attack first, forming substances that are easily soluble in water or gases that fly away These substances will not create oil and gas On the contrary, substances that are difficult to decompose (such as proteins, fats, alcohols, waxes, etc.) ) will be deposited to form a sediment layer on the seabed These are the first organic materials of oil and gas Over millions

of years, these substances will form the initial hydrocarbons

According to author Petrov, plant fatty acids are usually unsaturated fatty acids γ-lactone and then form naphthenes or aromatics

These ketones can condense to form hydrocarbons of mixed structure, or into aromatic alkyl substances

Based on the above process, hydrogen must be present to saturate the olefins to form paraffins And two hypotheses are put forward about the formation of H

-Due to radioactive rays in the ground, H2 is produced This hypothesis is less convincing

-Due to the anaerobic bacteria at the bottom of the sediment, they have the ability to ferment organic matter to produce H2 Author J.Bell has found 30 types of bacteria capable of fermenting organic matter to produce H2 These bacteria are often found in lake water and even

in sediment, which is the source of H2 for the reduction process

In addition to bacterial factors, many scientists also believe that there are a series of other factors such as temperature, pressure, time, presence of catalysts (metals Ni, V, Mo, minerals) clay ) in the sediment layers creates favorable conditions for the reaction to occur

The theory of organic origin of petroleum allows us to explain many real-life phenomena For example, petroleum is in almost different places, and the difference may be due to the original organic material For example, :if the original organic material is rich in fat, paraffinic oil can be created…

The original hydrocarbons of oil and gas often have very large molecular weights (C30 -C40) or even higher These organic substances located in the sediment layer will undergo many chemical changes under the influence of temperature and pressure pressure, catalyst (clay minerals) It is seen that for every 30m of sinking, the temperature increases from 0.54-1.2ºC And the pressure increases from 3-7.5at Thus, at a greater depth The temperature and pressure increase and in the oil and gas sediment layer, the temperature can be up to 100-200ºC and the pressure is from 200-1000at Under such conditions, hydrocarbons have large molecular weight, long chains, and complex structure Impurities will be thermally decomposed to form substances with smaller molecular weights, simpler structures, fewer aromatic rings, etc

Time is also a factor that accelerates the cracking process Therefore, the older the oil is, the deeper the sinking depth is, and the more hydrocarbon molecules the formed oil contains with the lower the molecular weight Deeper Moreover, methane is the most stable gas, so it has the highest concentration That's why when increasing the depth of oil and gas exploration wells, the probability of finding gas is often higher oil leaves

3 The conversion of organic matter into petroleum

A question that arises is how the components of organic matter participate in the oil creation process? There are two basic groups of views:

Some authors believe that during the postmortem transformation of living things, all their components lose their individuality and the general mixture of organic matter turns entirely into petroleum That is the hypothesis of total conversion to oil This view requires an explanation of the source of the large amounts of hydrogen needed to reduce organic matter On the contrary, the concept of converting a part of organic material into oil does not require this organic source, because the part converted into oil already has reducing properties

The problem of transforming all or part of the original organic materials is related to the problem of regulating their accumulation.Those who defend the total transformation view believe that there is an accumulation of a large mass of starting material, while those who support the partial transformation view believe that petroleum is formed from organic material dispersed in the sedimentary rock

According to Xtadnikov, the starting material is mainly high-grade plants, while the oil-forming component is mainly vegetable resins, and secondarily waxes and sometimes licnin The original material accumulates and completely disappears when oil is formed The appearance of oil hydrocarbons begins with the petrification phase, with bacterial activity being the basis Oil production continues and also ends in the postnatal transformation phase, when the primary factor causing hydrogenation of organic matter is the primary phase The architecture of the original organic matter is completely destroyed Favorable for this process is high pressure and temperature of about 2000 C The intermediate formation between organic material and oil, according to him, is viscosity (manta) with a multi-ring structure, also known

as "primal oil" ( protopetroleum )

According to A F Dobrianxki, the original materials were floating organisms, partly remains of land plants and animals All of this rotten sludge participates in the oil creation process, which occurs in the post-production transformation phase under the influence of high temperature (but not exceeding 150-2500C) and alumosilicate catalyst It is the process of destroying carboxyl and hydroxyl The hydrogen required for the reduction of organic matter is obtained during the redistribution of hydrogen among the original organic constituents The type of oil originally created was heavy aromatic and then gradually methanized under the influence of heat and catalyst The intermediate formations between the starting organic material and heavy oil are oxyasfan and lubricating oil (manta), similar to Xtadnikov's:primary oil

According to V B Porfirev and I V Grinberg (1949), organic materials initially accumulate

in concentrated form and completely or almost completely form oil The transformation of organic matter into oil occurs in the post-diagenetic and metamorphic phases The essence of this transformation is thermal fracturing at 3000C and pressure above 100 atm, the hydrogen source is bottom sediment water According to him, oil creation in the base zone is impossible, because in this zone the depth of subsidence is not enough to reach the necessary temperature

and pressure Therefore, all oil reservoirs in the basement area are related to the movement of oil from neighboring geosynclinal areas

The weakness of these views is the lack of geological basis First of all, large concentrations

of plant remains, although common, due to the conditions of accumulation, cannot preserve the light hydrocarbons that make up the oil The idea that the oil creation temperature is about 3000C contradicts some components of oil that are unstable at high temperatures, such as porfirin On the other hand, their opinions about the hydrogen source needed for the reduction (hydrogenation) reaction are completely artificial

The second direction is supported by geologists According to this view, only the most reduced fractions of organic matter in dispersed form participate in the oil formation process These are lipids (fats), lipoids (wax, sterin, fotfotite ), they are soluble in organic solvents Organic matter dissolved in organic solvents today is called “bitumen”

If the content of “bitumen”-containing components is insignificant in organic matter, then even the largest concentrations of plant remains can yield only a negligible amount of petroleum Meanwhile, many oil reservoirs in the world contain huge amounts of oil Therefore,

I M Gubkin's view of "oil generation" or "stinking mud theory" was formed

The basic sources of hydrocarbons that enter the composition of petroleum can be as follows:

- The most recent research projects have proven that in many living organisms, hydrocarbons

of the oil series exist quite widely These discoveries allow us to hypothesize that hydrocarbides contained in living matter were transferred directly into the sediment Modern marine sediment research has proven the realism of this view P Smith (1965) observed in the present mud liquid hydrocarbons (of all three series: methane, naften and aromatic), which dating according to radioactive C14 content proved that these hydrocarbons were of the same age as surrounded by mud Research by V V Veber and A I Gorxki also confirmed that the hydrocarbons in bitumen

of modern sediments are partly transferred directly from the remains of dead organisms and partly are newly formed formations due to the living activities of living organisms microorganism

- Some new hydrocarbides are formed from materials other than hydrocarbide, under the influence of microorganisms The significance of this source is little studied

- New hydrocarbides are formed from materials other than hydrocarbide or from pre-existing hydrocarbides whose structure is changed under the influence of high temperature, with the participation of catalysts In fact, no one denies this source, but some authors evaluate its role too highly There needs to be more complete research on this source, especially research under natural conditions

*Organic matter conservation factor:

When these products reach the bottom, they will create a reducing environment and they are not destroyed by bottom-dwelling animals, so people often pay attention to environments with many floating organisms and few bottom-dwelling organisms

Organisms are rapidly buried with large sediment loads and have conditions that promote rapid compaction and submergence of those sediments, subjecting them to the higher temperatures found in coastal environments, not very deep From there, people can imagine the oil-producing environment

Crude oil itself has good solubility when lying in source rock, but when transferred to rock containing crude oil, the composition and chemical formula will change and it will not be soluble This proves that some precursors of petroleum such as fatty acids and alcohols are more soluble in water than the hydrocarbons produced from them

Table: Solubility of paraffins, acids and alcohol During the oil and gas generation process: the formation of microscopic cracks is limited to very large depths, corresponding to the period of strong oil generation when organic matter present in large quantities in the source rock has been transformed into petroleum components

III CONTROLLING FACTORS

1 Physicochemical factors

- Temperature plays an important role ( < 2700C)

-Pressure increases rapidly with burial

- A catalyst such as silicate acid must be present because it has been proven that today's crude oil is formed by a catalyst

- Oil and gas are formed in subsidence areas, the more subsidence there is, the higher the temperature and pressure

- Organic substances form with a sediment thickness of more than 2000m Therefore, subsidence is a basic factor in the formation of hydrocarbons

2 Biochemical factors

It is found that sludge contains a large number of bacteria with a level of several tens of thousands to several million per 1cm3 Their levels decrease rapidly with depth, the bacteria consume H2 and I by using H2 to reduce carbon dioxide and sulfate and give CH4, sulfides

CO2 + 4H2 → CH4 + 2H2O SO4 + 4H2 = H2S + 3H2O + Base

R=C 5 H 11 R=C 6 H 13 R=C 7 H 15

R – COOH 10700 2200 3

R - OH 26000 5600 1800

This reaction occurs easily thanks to the presence of a catalyst Changes in organic matter in sediments

Scientists give a problem: after one hour, the next generation of an individual bacteria can create 40,000 petroleum This cannot exist because bacteria destroy hydrocarbons Also due to the disinfectant effect of sea water and the amount of organic matter present But on the contrary, bacterial growth is extremely fast Bacteria have 3 roles:

-Creates favorable conditions for the development of the reducing environment radius

-Creates a significant amount of organic matter that produces hydrocarbons within their cells -Provides part of the energy needed for the synthesis of hydrocarbon molecules

3 Radioactive elements

Radioactivity is an important factor in the formation of petroleum; some shales contain more

or less radioactive uranium, tobium and kalium compounds On the other hand, fatty acids are bombarded by particles, producing a petroleum-like liquid But today radioactivity cannot produce hydrocarbons on a large scale, but only produces less than 1% of new sediment by weight

The hydrocarbons formed during rock formation and especially immediately after deposition

in the upper layer of mud under the action of bacteria whose proliferation can be an important source of organic and hydrocarbon sources The following processes take place during compaction where the gradual increase in temperature will gradually increase the conversion process

It was found that many of the basins contained oil and that the richest basins were located adjacent to the existing sedimentary basins These basins show succession in space and time Oceanographic and sedimentological research gives us a better understanding of the landscape and sedimentary mechanisms of the new basin One can summarize the sedimentary environment as a predominantly quiet water bath There is rapid burial of sedimentary materials, allowing good preservation of organic materials

Areas with these conditions are: bays, bays, and estuaries This is where the main organic materials are deposited and will create cellulose debris This will be the origin of natural gas reservoirs

Low-lying areas and more or less deep basins typically have a quiet environment far from water sources and there will sediment quite quickly to fill up organic matter Finally, at the base

of the continental slope, continental sediments will slide and pile up on top of each other in the form of mudflows that can form important hydrocarbon basins

IV CURRENT OIL ORIGIN ISSUES

Although there are still many unclear and debated issues, the issue of the origin of oil has been basically resolved Today, the organic origin of most oil and gas accumulations is beyond doubt The ability to convert matter and its various components into oil has been demonstrated

It has been established that the transformation of organic matter into oil can occur in different

ways, when suitable conditions are created for each of them It is necessary to quantitatively evaluate these transformation processes and clearly explain the role and meaning of the factors causing change in specific geological conditions If the process of converting organic matter into oil has been resolved to a large extent, the migration processes (especially primary migration) of oil still have many problems that must be further researched and resolved It can

be said that in petroleum geology, this is also the field with the most unclear issues

V REFERENCE