Regarding the theory of the origin of oil, scientists have not come to a consensus. This is a very complex issue, and the problem of resolving it is not yet capable of either the geology of gas and oil, or all of the natural sciences that are currently available to mankind. Not only theoreticians, but also practitioners speak about the origin of oil. The famous oil geologist I.M. Gubkin in the thirties of the last century wrote a lot about this and interestingly, discussing various theories of the origin of oil. In general, we can only guess what kind of processes have passed over billions of years under the earth’s crust, our planet is in many ways still a mystery to us. Man knows little about the true course of geoevolution processes, so theories of the origin of oil are very numerous.
Two main theories
When humanity gains full knowledge about the conditions that contribute to the emergence of oil, when it studies how it is formed in the earth’s crust, when it gets acquainted with all the structural forms of reservoirs, their lithological features that are favorable for the appearance and accumulation of oil, only then exploration and prospecting for deposits will be carried out really appropriate. As soon as geological science began to develop, two main theories of the origin of oil were outlined. The first connects its formation with living matter. This is an organic theory of the origin of oil. The second suggests that both gas and oil arose due to the synthesis of hydrogen and carbon at high pressures and temperatures deep in the earth's crust. This is an inorganic theory of the origin of oil.
History claims that organic theory appeared later inorganic: until the mid-nineteenth century, oil was extracted only where it came in contact with the surface of the earth - in California, the Mediterranean, Venezuela and some other places. The German scientist Humboldt suggested how oil is formed: just like asphalt, as a result of volcanoes. A little later, in the second half of the nineteenth century, chemists were already able in laboratories to synthesize acetylene C 2 H 2 with methane hydrocarbons. Even later, our Dmitri Ivanovich Mendeleev presented his own carbide, rather than organic, theory of the origin of oil to the world. Geologist and scientist Gubkin criticized her fiercely.
Mendeleev and Gubkin
In 1877, the master made a statement in the Russian Chemical Society regarding the hypothesis of the origin of oil. It was based on enormous factual material, and therefore immediately became popular. Judging by the evidence presented, all of the discovered deposits at that time concentrated on the edges of the mountain-folded formations, they are elongated and located near the zones of large faults. According to Mendeleev, water gets through the faults deep into the Earth and reacts with metal carbides, thus contributing to the formation of oil, which then rises and forms deposits. Mendeleev’s formula is as follows: 2FeC + 3H 2 O = Fe 2 O 3 + C 2 H 6 . Judging by his hypothesis (how oil is formed), this process always occurs, and not only in distant geological periods.
IM Gubkin criticized carbide theory everywhere. This option cannot satisfy a person who knows the geology well, who is sure that the oil is perfectly formed even where there are no faults at all that conduct water to liquid carbides. Such cracks simply do not exist in nature - from the core of the Earth to the surface. The basalt belt will not allow either water to penetrate deep into the water, or finished oil to rise outside. Especially since all the oil produced today from vast depths speaks against this theory. Gubkin’s argument was also that oil formed in an inorganic way is optically inactive, while natural oil is active, even capable of rotating in the plane of polarization of light.
Cosmos - The Third Theory
The cosmic theory of how oil is formed was very popular. Today, with the advent of modern technology into space, it has suffered a crushing fiasco. Russian geologist N. A. Sokolov unveiled his theory of the cosmic origin of oil back in 1892, based on the fact that hydrocarbons have always existed on our planet in its most pristine form, and they formed at high temperatures, when the Earth was just forming. As the planet cools, it absorbs oil, dissolving it in liquid magma. After the formation of the solid crust of the earth, magma, as it were, gave off hydrocarbons, which, through cracks, climbed to its upper parts, where they thickened from cooling and formed some clusters. Sokolov’s arguments were that hydrocarbons were discovered in a mass of meteorites.
Gubkin criticized this theory to the nines and blamed it and accused it of being based on purely theoretical calculations that were never confirmed by geological observations. In general, he was sure that there was almost no inorganic oil in nature, and that which was there could not be of practical importance. The bulk of the oil deposits still contains a substance that has gone through all the stages of oil formation, and it is in an organic way. The subsequent discussion of this problem took place for almost a hundred years, with the same debate and lack of agreement. Soviet oil scientists put forward the most reasonable theory of the inorganic origin of oil.
Scientists of the Soviet Union
Kropotkin, Porfiryev, Kudryavtsev and other like-minded people tried to prove that from hydrogen and carbon, which are a sufficient amount in magma, radicals CH, CH 2 , CH 3 are formed , which are released from it together with oxygen, which serves as the starting material in cold zones for oil formation. Kudryavtsev was sure that the abiogenic origin of oil allows it to pass along with the gases into the sedimentary shell of the planet through deep faults precisely from the mantle of the Earth. Porfiryev objected that the oil did not come in the form of hydrocarbon radicals from the deep zones, but already completely possessing all the properties of the finished natural oil, making its way through porous rocks. He could not answer only the question of how deep the oil was before the migration? There is no doubt that in the subcortical zones, but this whole theory is just as unprovable as the previous ones.
The inorganic origin of oil was supported by the following arguments:
1. There are also deposits in fundamental crystalline rocks.
2. Impurities of gas and oil were found together with hydrocarbons in emissions of volcanoes, in "explosion tubes", in space.
3. Hydrocarbons can be obtained by laboratory tests, creating conditions of high pressures and temperatures.
4. Hydrocarbon gases and liquid hydrocarbon fluids are present in wells that open the crystalline foundation (in Sweden, Tatarstan and other places).
5. Organic theory cannot explain the existence of huge concentrations of oil and giant fields.
6. Gas deposits are of Cenozoic age, and oil is of post-Paleozoic age on ancient mountain platforms.
7. Oil fields are most often associated with deep faults.
Organic theory
In recent years, a lot of publications with new data have appeared. For example, liquid oil is found in the oceans, in their spreading zones. Most of these facts speak of the inorganic origin of oil. However, anyway, it is justified rather sparingly and weakly. Therefore, she still has very few supporters. The vast majority of geologists both abroad and in our country adhere to the organic theory of the occurrence of oil. Why is this theory so attractive?
The biogenic origin of oil implies its occurrence from organic matter of sedimentary subaquatic deposits. The nature of this process is clearly staged. Proponents of biogenic theory are convinced that oil is a product obtained through conversion from organic matter. These are the remains of the animal and plant world in sedimentary deposits of marine origin, of which literally grams are accounted for per cubic meter of saline sediment, but up to six kilograms can be accounted for in the oil shales for the same cubic meter of sediment. In clay - half a kilogram, in siltstones - two hundred grams, in limestone - two hundred and fifty.
Two types of organic matter
Sapropel and humus - every person who is fond of crop production knows what it is. If organic matter accumulates under water, where air access is insufficient, but it is there, it rots, humus is obtained - the main part of the soil that provides fertility. If, under water, but without access to oxygen, organic matter accumulates, then a "slow distillation" takes place, and the chemical reduction process is rotting. Small pools with stagnant water always have a huge amount of blue-green algae, plankton, including arthropods, which do not live long and die in huge numbers.
At the bottom, a powerful layer of organic sludge is formed - sapropel. Such are the coastal parts of the seas, lagoons, estuaries. When dry distilled, sapropel produces twenty-five percent of the weight of oil-like fatty oils. And the formation of oil is a process so long and complicated that it is impossible for a person to follow all its stages, he only finds the result - huge oil fields and deposits. And the processes have been going on for thousands of years in the oil source formations, where the most diverse deposits were formed at the bottom of the oceans and contained dispersed matter of organic origin in quantities not lower than clarke - four hundred grams per cubic meter.
Potential
Oil deposits with the highest potential are clay-carbonate deposits containing sapropel organic matter. Such deposits are called dominicites. They exist in all Precambrian strata, in the Phanerozoic systems, and at the same stratigraphic levels of completely different continents. How did it happen? Three and a half billion years ago, life was born on earth. In the Cambrian era, the water shell of the Earth already had the most diverse forms of organics. The Early Paleozoic was represented by the immense seas and oceans, where algae and invertebrates already had a huge number of species.
And far from all this organic world immediately rushed to land. The best living conditions were created in reservoirs at a depth of sixty to eighty meters - most often these are the shelves of the underwater borders of the continents. The closer to land, the more organic matter in the sediment. Inland seas contain up to fifty percent of all deposited organic matter. The best conditions for creating oil are the coastal parts of the seas. The homeland of oil is the ancient seas, not swamps in freshwater basins.
Oil Formation Stages
Academician Gubkin argued that oil production cannot do without going through certain stages. The first is sedimentogenesis and diagenesis, when gas and oil source sediments are being formed, that is, the original organic matter. The first stage brings with it such biochemical processes in which kerogen and an abundance of gaseous substances are formed, which gradually dissipate.
Some of them dissolve and concentrate, sometimes even of interest in industrial production (fifty billion cubic meters of methane in an African lake, for example, or in Japan, gas is also extracted from the sea, in which up to ninety-seven percent of methane). However, oil has not yet formed at this stage. But further immersion leads the scout to the source rocks of the catagenesis zone, where ammonia, hydrogen sulfide, methane, carbon dioxide, and with them liquid hydrocarbon products, already arise from the original organic matter.
Phases and Zones
The main phase is oil formation in the catagenesis stage at a depth of two to three kilometers of sediments at temperatures from eighty to one hundred and fifty degrees Celsius. The optimal conditions are precisely those in which the decisive factor is high temperature. Oil and gas generation also has specific zones in depth. Up to one hundred and fifty meters, the biochemical zone, which is characterized by the development in the organic matter of biochemical processes with the release of gases.
From one to one and a half kilometers down - the transition zone, where all biochemical processes decay. The third zone from one and a half to six kilometers is thermocatalytic, it is especially important for the formation of oil. And the fourth is gas, where methane is formed mainly. It can be seen that the process begins with the formation of gas, and accompanies oil formation at all stages, and completes this process. This zonality is vertical, and the distribution of hydrocarbons in the fields is horizontal.
Production
Previously, oil was extracted where it almost comes close to the surface. Now its production has increased many times, and therefore the wells simply amaze with their length. The longest were drilled in the USSR: on Sakhalin - much more than twelve kilometers, and on the Kola Peninsula - 12262 meters. In Qatar, a horizontal well is more than twelve kilometers, in the United States - two nine-kilometer wells. In the Bavarian mountains of Germany there is the same nine-kilometer well from which nothing was mined and not mined, although they spent three hundred and thirty-seven million dollars on it. In Austria, a small oil field was found, which unexpectedly turned out to be much more explored, but oil was discovered at a depth of more than eight kilometers. Upon closer inspection, this cluster turned out to be not oil, but gas, which was impossible to produce - the geological features of this section did not allow. But they still drilled the well, but found nothing at all, not even shale, which could have been extracted.
All countries need oil. Due to her absence, wars constantly begin. It is now mined in unprecedented quantities. The earth is already literally bloodless. Energy experts have calculated how many years the oil in the bowels of the Earth will last. And it turned out that already proven reserves were left for only fifty-six years. Of course, it will not completely disappear. People already know how to extract oil from shale, oil sand, from natural bitumen and much more. Venezuela will have enough oil for a hundred years, Saudi Arabia - for almost seventy, Russia - for less than thirty years it remains to be an oil and gas giant.