Oil Formation

 

The First Carbon in the Universe:

The common belief among physicists today is that the carbon in the universe is largely formed by nuclear reactions that take place at the centers of stars. In summary, this process takes place as follows: Three alpha particles (helium atom nuclei), each consisting of two protons and two neutrons, fuse together, resulting in carbon atom nuclei consisting of six protons and six neutrons. This process is very rare. Because first of all, it is unlikely that three alpha particles will come together and fuse together. Second, even if three alpha particles fuse, the resulting high-energy carbon nuclei are unstable. The vast majority of them disintegrate in a short time, and the nuclei, which lose energy by emitting only gamma, manage to transform into stable carbon atoms. According to estimates, only four of every 10,000 carbon atom nuclei formed by the triple alpha process turn into stable carbon atoms.

 

The characteristics of the crude oil are determined by the geological history of the beds in which they are found. Louisiana and Nigerian crude oils are similar; both are made up of similar marine remains. Far Eastern oils are usually waxy, black or brown in color, low sulfur, and similar to Central African oils; these are based on terrestrial deposits. Middle Eastern oils are low in wax, but high in sulfur. Western Australian oil is light and honey-colored, North Sea oil is waxed, green-black in color. The characteristics of the oils in the USA are very diverse due to the very different geological histories of the regions. The oldest oil-bed rocks are more than 600 million years old, while the youngest ones are around 1 million years old. Most of the oil deposits discovered and found are 10-270 million years old.

The most critical factor in the formation of oil and gas deposits is the subsurface temperature that increases with depth. While the formation of petroleum hydrocarbons can rarely occur at temperatures lower than 150 ° F, hydrocarbons formed at temperatures above 500 ° F decompose and carbonize; the ideal temperature range is between 225-350 degrees.

Anterior cambrium layer; They are layers from the formation of the earth (~ 4 billion years ago) to the time when the first known multicellular organisms began (550 million years ago). Since the oil is considered to be of organic origin, drilling is not made up to these layers.

In Paleozoic and Mesozoic times (550-65 million years ago) dense forests and seas were filled with plants and animals. Over time, some of those who died or lived were protected from degradation by covering with sand or mud, and the process of oil formation began. The process sometimes took place with the sliding of mud, displacement of sand dunes, sometimes volcanic explosions, sometimes with meteorites colliding with the earth and throwing massive clouds and dust. These collapsed layers were subjected to increasing pressures and therefore rising temperatures with the new layers added on them.

As the earth crust slid, these layers that had begun to form were pushed deeper and deeper. The center of the earth, as is known, is very hot and the rocks are in a liquefied state. The chemical reactions that took place for thousands of years with the bacteria that were active in all these conditions created the components of natural gas and crude oil.

In Paleozoic and Mesozoic times (550-65 million years ago) dense forests and seas were filled with plants and animals. Over time, some of those who died or lived were protected from degradation by covering with sand or mud, and the process of oil formation began. The process sometimes took place with the sliding of mud, displacement of sand dunes, sometimes volcanic explosions, sometimes with meteorites colliding with the earth and throwing massive clouds and dust. These collapsed layers were subjected to increasing pressures and therefore rising temperatures with the new layers added on them.

As the earth crust slid, these layers that had begun to form were pushed deeper and deeper. The center of the earth, as is known, is very hot and the rocks are in a liquefied state. The chemical reactions that took place for thousands of years with the bacteria that were active in all these conditions created the components of natural gas and crude oil.

The organic matter was buried under sand and mud, as the pressure increased, the oil flowed into the rocks near it. Although rocks look like solid masses, they contain many pores (pore) and some rocks have larger and larger pores than others. There are three basic rock types; volcanic, metamorphic (metamorphic) and sedimentary (or sedimentary) rocks. Oil is mostly found around sedimentary rocks, but not all sediment rocks contain oil. Only 2% of the organic matter turns into oil, and only about 0.5% can be handled. Hydrocarbons are lighter than water and migrate upward from porous rocks until they are captured by non-porous layers (traps).

Conventional oil and gas deposits do not show a regular distribution both in terms of location and time. Large oil and gas deposits are located in a small number of basins or classical oil regions less than 20000 ft (6.1 km) deep. This uneven distribution is related to the forming or breaking properties of the layers.

There are more than 600 basins and sub-basins in the world and most of them are concentrated in several geological regions; possible calculations show that up to 80% of the original oil reserves are concentrated in 10 regions. The Arabian Platform and the Zagros Belt (Saudi Arabia-Iran-Iraq) have the largest known and discovered reserves.

Although it occurs in all geological periods, 95% of all reservoirs in the world have been formed in six geological time intervals according to known hydrocarbon deposits.

Source rocks (layers rich in organic substances that produce hydrocarbons) are the first key to any important petroleum system. Source rocks are deposited and preserved in various marine and terrestrial geological deposits.

When the distribution of these sediments formed from the Precambrian time in the world is examined, it is seen that 90% of them belong to six geological stages. The two Mesozoic phases (Upper Jurassic and Middle Cretaceous) are estimated to contain more than half of all defined hydrocarbon reserves. Source rocks of this age are found in the Middle East, Siberia, United States, North Sea, Venezuela and Mexico, where the world's important oil deposits are located.

 

Origin of Oil:
Since the 1800s, various opinions have been put forward, researches and experiments have been made, and theories have been produced regarding whether the oil is inorganic or organic based, and what kind of substances or compounds its origin is based on. These debates from the past to the present have ended with the acceptance of the organic origin theory, although there are still a few opposing views. Below is a brief summary of these theories.
According to a theory first put forward by Berthelot (1866) and supported by Mendeleev (1877 and 1902) oil is of inorganic origin. Chemists, who obtained materials such as methane, acetylene and benzol in the laboratory, claimed that the petroleum in nature was formed by chemical reactions and volcanic events underground.

At the beginning of the 20th century, some scientists suggested that oil was of igneous origin. According to Mendeleev's theory, the iron carbide in the mantle interacts with water leaking underground to form methane and hydrocarbons.
Peyve (1956) and Subbottin (1966) suggested that based on the hydrocarbon gases emanating from large and deep faults, these gases exit the mantle and are stored in the crust and converted into liquid petroleum. In this case, it will be possible to reach endless oil resources by opening extremely deep drillings; however, oil is mostly found in sedimentary basins. However, some scientific data invalidate the inorganic origin theory; For example, substances in petroleum such as porphyrin, pyridine and chlorophyll cannot be obtained by inorganic means,
Large molecular weight hydrocarbons cannot be formed by inorganic reactions. The polarized light deflection feature of petroleum compounds does not exist in any inorganic material other than quartz and cinnabar.

Most of the oil deposits are far from magmatic activity areas and sedimentary rocks
are in. Oil does not increase towards the depths of the earth's crust,
on the contrary, oil is more commonly found in young cover rocks:
As a result, it cannot be said that the oil is of inorganic origin.
Some researchers admit that oil is of both animal and vegetable origin (biomass origin); For example, by the distillation of fish and other animal meats, substances similar to petroleum components are obtained. It has been suggested that the oil may be of terrestrial plant origin due to the extraction of oil from coal and methane gas in the marshes. However, the absence of coal in oil fields, the absence of petroleum derived from terrestrial plants in limestones, and the chemical differences between pitch derived from lignite and petroleum show that terrestrial plants do not have a significant effect on oil formation. An original relationship can be established between marine plants and marine sediments. The most important of these are algae and diatoms. Diatoms float on the surface (several meters in depth) of oceans and lakes and over time produce some types of hydrocarbons. During this time, they also become the food of various sea creatures whose skeletal structures resemble sand (containing silicon compounds). Both formations store chemical energy through photosynthesis and increase their swimming ability.

These raw materials, which are collected in mixed form with sediments or deposits in the underground layers, undergo transformation with various and complex physical, biochemical and chemical reactions depending on the parameters of pressure, temperature and time.

 

Oil Formation Parameters:

Temperature: As the burial depth increases, the most important event that occurs is the increase in temperature. Increasing temperature with depth is defined as "geothermal gradient".

The world geothermal gradient average is 23.5 ° C per 1 kilometer. This value varies regionally depending on factors such as the thermal conductivity of the substances in the lithology and the amount of groundwater.

The temperature at any depth can be found in the equation below.

 

Tf = Ts + (D x G)
Tf = formation temperature, ° C, Ts = average annual surface temperature, ° C ("surface", 3 meters

defines the depth), G = geothermal gradient, D = depth, meter

Pressure: Pressure is very important in the migration of the oil that is formed, but pressure is also an important parameter in the formation of oil. As the depth increases, the pressure increases; for example, the pressure at a depth of 580 meters is 40.4 kg / cm² (or 575 psi).
Time: Hydrocarbons are partially stable at depths close to Earth, whereas high enough temperatures and time were required to trigger molecular transformations. For roughly 100 million years, the conversion in organic matter remains very low. When the temperature reaches 50 ° C and the atomic bonds in the kerogen begin to break at depths of about 2200 meters, oxygen outputs, CO2 and H2O are formed and the first petroleum products containing sulfur, nitrogen and oxygen, especially asphaltenes and resins, and gas products depending on the structure of organic substances. begins to occur.

 

It is formed by various hydrocarbons that combine certain minerals such as sulfur under high pressure. It was formed by the transformation of dead plants and animals millions of years ago into a jelly-like mass by being trapped under the pressure of the earth's crust and ocean over millions of years, covered with a layer of sand and mud.

As the depth of this gel-like sediment accumulation increased with the movements of the earth's crust over millions of years, the pressure on the mass increased and caused it to be compressed into a much thinner layer than the beginning.
In addition, the natural heat of the earth had an effect that would cause a reaction on this mass under intense pressure, and in time caused the gel to transform into today's known oil form.

Today, the difference between the quality of all the oil extracted in the world is due to the differences between this pressure and temperature and the formation processes.

Oil is also called "fossil energy", "fossil fuel" because of this formation, and it is definitely not "renewable energy" due to the long formation process.
Originally the primary use of petroleum was as a lighting fuel, once distilled and made into kerosene.
After a short while, the demand for gasoline started to increase rapidly as Ford triggered the automobile industry and the range of what could be done with internal combustion engines expanded.
Today, oil is seen as a precious mineral that is traded like gold and diamond around the world.
Most people believe that oil is mostly used in the form of gasoline or gasoline equivalents to power internal combustion engines.
However, apart from this area of ​​use, it is also used as asphalt and water-repellent insulation material even in its most waste form.

Oil is also an essential part of the chemical makeup of many plastics and synthetics. The most surprising possible use of oil for many people is that it also occurs in foodstuffs like beer and medicines like aspirin.

It is a fact that there is limited oil reserves in the world that will eventually be depleted. Although cheap, renewable fuel options are being created and developed instead, it is obvious that humanity will face a serious problem in the end.
The basic definition of petroleum includes only crude oil, but the common usage of the term is generally to include all liquid, gaseous and solid hydrocarbons found in a given mixture.
The basic basis is on hydrocarbons and all hydrocarbons are the same as they contain hydrogen and carbon atoms. Differences; It is due to details such as the number of carbon they have, their saturation level, and their aromaticity.