GEOLOGICAL REGULARITIES OF THE LOCATION OF OIL FIELDS
| Parameter name | Meaning |
| Article subject: | GEOLOGICAL REGULARITIES OF THE LOCATION OF OIL FIELDS |
| Rubric (thematic category) | Education |
World oil reserves by age of oil-bearing rocks are distributed as follows:
Upper Paleozoic rocks - about 20%,
Mesozoic rocks - about 60%,
Cenozoic rocks - about 20%.
Deposits of Paleozoic strata. Oil-bearing basins, whose deposits are concentrated in Paleozoic deposits, are located mainly in the sedimentary cover of ancient platforms with a Precambrian basement, more often on their margins, bordering on Phanerozoic accretionary-folded systems.
On the American continent, sedimentary rocks of the Upper Paleozoic (Devonian, Carboniferous, Permian) contain about half of the oil reserves of the United States and Canada. In the USA, the largest are the Permian (Texas, New Mexico, Oklahoma) and Western Inner (Oklahoma, Texas, Kansas, Iowa, Nebraska, Missouri) oil and gas basins. In the Permian basin, the main oil reserves are confined to the Permian subsalt deposits, and in the Western Inner Basin, to the terrigenous-carbonate rocks of the Carboniferous and Permian age. In Canada, the largest is the Western Canadian oil and gas basin, where more than half of the reserves are confined to Devonian reef rocks.
Large oil deposits in Devonian and Carboniferous sandstones are located in northern Africa, in Algeria and Libya (Sahara-East-Mediterranean megabasin).
The largest in Kazakhstan Tengiz field (Caspian basin, Guryev region) is confined to the reef massif of the Lower-Middle Carboniferous with an area of 400 km2. The height of the deposit is more than 1140 m.
In Russia, in the rocks of the Paleozoic, oil deposits are common in the European part, where the deposits of the Volga-Ural (Romashkinskoe, Tuimazinskoe, Bavlinskoe, Osinskoe, etc.) and Timan-Pechora (Ukhta, Yaregskoe, etc.) oil-bearing basins are located. The largest deposits are confined to the Devonian strata and more often to their Pashian terrigenous layers. Some of the deposits are localized in the rocks of the Carboniferous age, mainly in the Tula and Bobrikov layers, as well as in the rocks of the Permian age.
Deposits of the Mesozoic strata. Oil basins, the deposits of which are concentrated in Mesozoic rocks, are usually located in the sedimentary cover of young epi-Hercynian platforms, also called plates (Gulf of Mexico, West Siberian basins), as well as on the outskirts of platforms adjacent to Alpine fold systems (Persian Gulf basin) .
Oil and gas basin Gulf of Mexico located in the depression of the bay of the same name in the United States, Mexico, Cuba, Guatemala and Belize.
The Persian Gulf basin is confined to the eastern margin of the Arabian Plate in Iraq, Kuwait, Saudi Arabia, the United Arab Emirates, Iran, Syria, Qatar and other countries. The largest deposits of the basin occur mainly among the strata of organogenic limestones and sands of the Upper Jurassic and differ large reserves and high production rates. Thus, the most famous oil and gas field of Saudi Arabia, Ghawar, is confined to a swell-like uplift 230 km long and 16–25 km wide and is located in the depth interval of 2042–2576 m. The thickness of the productive horizon is 40–45 m. 750 to 1500 tons of oil per day, the initial recoverable oil reserves of the field were estimated at 10 billion tons, and gas - at 1 trillion. m 3.
Large oil fields are located in the Ural-Emba region of Kazakhstan (Caspian basin) among terrigenous Meso-Cenozoic deposits of salt-dome structures.
In Russia, the largest deposits of the West Siberian basin are concentrated in the Mesozoic deposits, incl. Samotlor, confined to six local uplifts in the southern part of the Tarkhovsky swell of the Nizhnevartovsk dome. The thickness of the sedimentary cover in the area of the field is 2700 - 2900 m. Seven oil deposits are located in the depth range of 1610 - 2230 m. The deposits of the Terek-Caspian (Tersko-Dagestan) basin in the ᴦ region are also associated with the Meso-Cenozoic deposits. Grozny.
Deposits of Cenozoic strata. Oil fields concentrated in Cenozoic deposits gravitate towards areas of alpine folding. First of all, these are the largest deposits of Iran and Iraq in the Mesopotamian depression (Persian Gulf basin), the United States in the Mexican depression (Gulf of Mexico basin), as well as deposits in Venezuela (Maracaib basin).
Large oil fields are located in Azerbaijan, such as Bibi Heybat (South Caspian basin).
Russian deposits in Cenozoic deposits are known in the North Caucasus (Tersko-Caspian basin), in the Ciscaucasia (North Black Sea basin), on Sakhalin Island and in its water area (Sakhalin-Okhotsk basin).
GEOLOGICAL REGULARITIES OF LOCATION OF OIL FIELDS - concept and types. Classification and features of the category "GEOLOGICAL REGULARITIES OF LOCATION OF OIL FIELDS" 2017, 2018.
EARTH CRUST AND ECONOMY
Under our feet is solid earth - the earth's crust formed over a long geological time, composed of various igneous, sedimentary and metamorphic rocks, with a complex relief. The earth's crust is the main treasury of mankind. It is in it that the
the main fossil resources, without the extraction of which modern production is impossible. On the surface of the land, soils were formed on the parent rocks. Humanity lives on land, here people plow and sow their fields, build dwellings, create industry, pave roads. It is the surface of the land that is the area where a person can simultaneously use in production both the energy of solar heat coming from the Sun to the Earth, and the "concentrated" energy of the Sun, preserved in the depths earth's crust for many hundreds of millions of years in the form of coal, oil and other fossil fuels. The land surface is an area where a person can simultaneously use in production objects of modern life of organisms and the results of ancient life of organisms - a significant part of sedimentary and metamorphic rocks, including limestone, iron ore, apparently bauxite and many other minerals.
The opportunity for a person to put at his service not only
to solar energy, plant and animal resources, river energy, soil fertility, but also natural energy and raw materials hidden in the bowels of the earth's crust are of great importance in the development of productive forces. Over time, the value of the riches of the earth's crust is increasing more and more.
Resources of the earth's crust
The thickness of the earth's crust is very large. We know best of all its upper stratum, which is successfully explored by geophysical exploration methods. To calculate the content of various resources in this stratum, its thickness is conditionally taken as 16 km.
The main elements of the earth's crust are oxygen (47.2% by weight) and silicon (27.6%), i.e. only these two elements make up 74.8% (i.e., almost three quarters!) Of the weight of the lithosphere (up to depth at 16 km). Almost a quarter of the weight (24.84%) are: aluminum (8.80%), iron (5.10%), calcium (3.60%), sodium (2.64%), potassium (2.60%) and magnesium (2.10%). Thus, only 73 percent is accounted for by the remaining chemical elements, which play very big role in modern industry - carbon, phosphorus, sulfur, manganese, chromium, nickel, copper, zinc, lead and many others 1 .
In modern industry, the following 25 most important types of fossil raw materials are distinguished: oil, natural gas, coal, uranium, thorium, iron, manganese, chromium, tungsten, nickel, molybdenum, vanadium, cobalt, copper, lead, zinc, tin, antimony, cadmium, mercury, bauxite (aluminum), magnesium, titanium, sulfur, diamonds. To these types of raw materials for industry, it is necessary to add the basic chemical elements necessary for agriculture - nitrogen, phosphorus, potassium, as well as the main elements used in construction - silicon, calcium. Total 30 most important types of raw materials modern economy 2 .
If we arrange the first 30 chemical elements that are most common in the lithosphere (in order of their weight percent) and serve as raw materials in the economy, we get the following sequence, partly already familiar to us: silicon, aluminum, iron, calcium, sodium, potassium, magnesium, titanium , carbon, chlorine, phosphorus, sulfur, manganese, fluorine, barium, nitrogen, strontium, chromium, zirconium, vanadium, nickel, zinc, boron, copper, rubidium, lithium, yttrium, beryllium, cerium, cobalt.
Thus, comparing these two series of main elements - economic and natural - we will not see in the second series (natural) the following important types of raw materials: uranium and thorium, tungsten, molybdenum, antimony, cadmium, mercury, lead, tin, i.e. .nine elements.
We can say that basically the economy relies on those elements from the fossil wealth that are contained in the lithosphere in most compared to the rest: iron, aluminum, magnesium, silicon. It should be noted, however, that the ratios between the first and last of the listed 30 elements in terms of their content in the earth's crust reach a very large value: the former are tens of thousands and thousands of times more than the latter.
The aluminum and magnesium industry began to develop especially strongly in last quarter century. Iron alloys, where possible, began to replace scarce non-ferrous metals. developed strongly for recent decades and. ceramic
1 See V. I. Vernadsky. Fav. soch., vol. 1. M., Publishing House of the Academy of Sciences of the USSR, 1954, p. 362.
2 Oxygen and hydrogen are excluded from this list.
industry, which is based on the use of clays and sand. Ceramic products (pipes, tiles, etc.) replace more scarce metals. At the same time, dozens of relatively rare chemical elements, most of which serve as an additive to the most common metals in nature (iron, aluminum, etc.) and give their alloys new valuable qualities. Modern industry has entered a period of creation of heavy-duty metals (steel, cast iron, aluminum alloys, magnesium, titanium) and concrete. A ton of these new materials replaces the many tons of metals produced at the beginning of this century.
The bowels of the earth's crust can provide a population for a long time the globe varied resources.
People still know relatively little of the bowels of the earth's crust and, in fact, are only just beginning to learn their riches.
In order to be able to rationally use minerals, it is necessary to determine their reserves. There are geochemical and geological reserves. Geochemical reserves - the amount of a particular chemical element in the earth's crust as a whole and within any large area of it. Industry is primarily interested in geological reserves, that is, those that are of direct importance, can be mined, brought to the surface. In turn, geological reserves are divided into three categories: A - commercial reserves; B - explored reserves; C - probable reserves.
Some scientists of the capitalist countries write about the threat of depletion of the earth's interior. But the explored geological reserves of the main types of fossil raw materials and fuels are increasing, as a rule, at a much higher rate than their extraction. With the exception of chromium, tungsten, cobalt, bauxite and sulfur with pyrites, the ratio of production to geological reserves is not increasing, but decreasing. Mankind is increasingly provided with the main types of fossil raw materials and there are no signs of modern depletion of the earth's interior.
The geological reserves of minerals could be increased even more if in the capitalist countries the main resources of the earth's interior were not seized by a small number of large capitalist monopolies interested in high prices for fossil raw materials and fuels. In this regard, the largest monopoly companies strive in every possible way to slow down new geological exploration and often hide the true explored reserves of the most important resources of the earth's interior.
The fall of the colonial regime and the weakening of the power of large monopolies after the Second World War in many countries of Asia, Africa and Latin America led to intensified geological exploration and the discovery of new gigantic wealth: oil, gas, iron, copper, manganese ores, rare metals, etc. If we compare the mineral maps of pre-war and recent
years, you can see strong changes in the direction of greater uniformity in the distribution of the largest deposits of minerals through the exploration of those continents and countries whose resources were not previously used by the main capitalist countries.
Patterns of geographical locationmineral raw materials
Minerals are distributed over the land surface relatively unevenly.
The spatial distribution of minerals is determined by natural laws. The earth's crust is heterogeneous in composition. It shows a regular change in the chemical composition with depth. Schematically, the thickness of the earth's crust (lithosphere) can be divided into three vertical zones:
The surface zone is granitic, acidic, with the following typical elements: hydrogen, helium, lithium, beryllium, boron, oxygen, fluorine, sodium, aluminum, (phosphorus), silicon, (chlorine), potassium, (titanium), (manganese), rubidium, yttrium, zirconium, niobium, molybdenum, tin, cesium, rare earths, tantalum, tungsten (gold), radium, radon, thorium, uranium (less typical elements in brackets).
The middle zone is basalt, basic, with a number of typical elements: carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, calcium, manganese, bromine, iodine, barium, strontium.
The deep zone is peridotite, ultrabasic, with typical elements: titanium, vanadium, chromium, iron, cobalt, nickel, ruthenium-palladium, osmium-platinum.
In addition, a typical vein group of chemical elements with a predominance of metals is distinguished. Sulfur, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, molybdenum, silver, cadmium, indium, tin, antimony, tellurium, gold, mercury, lead, bismuth 3 are usually concentrated in the veins.
As one deepens into the thickness of the earth's crust, the content of oxygen, silicon, aluminum, sodium, potassium, phosphorus, barium, strontium decreases, and the proportion of magnesium, calcium, iron, titanium 4 increases.
In very deep mines, there is often a change in the ratio of elements as you go deeper. For example, in the mines of the Ore Mountains, the content of tin increases from top to bottom, in a number of regions tungsten is replaced by tin, lead by zinc, and so on.
3 See A. E. Fersman. Fav. works, vol. 2. Moscow, Publishing House of the Academy of Sciences of the USSR, 1953, p. 264.
4 See ibid., pp. 267-268.
5 See t;1 m e, p. 219.
Mountain building processes disrupt the ideal arrangement of typical groups of chemical elements (geochemical associations). As a result of mountain building, deep rocks rise to the surface of the Earth. The greater the amplitude of vertical displacements in the lithosphere, which is partially reflected in the amplitude of mountain heights, the greater the differences in the combination of chemical elements. Where the mountains have been severely destroyed by the exogenous forces of nature, a variety of riches of the earth's interior are revealed to man: all the treasures according to the periodic table.
The time of formation of various minerals is not the same. The main geological epochs differ greatly from each other in the concentration of various elements. There are also large differences in the concentration of minerals in one or another era across the continents.
The Precambrian era is characterized by ferruginous quartzites and rich iron ores (68% of the proven iron ore reserves of all capitalist countries), ores of manganese (63%), chromites (94%), copper (60%), nickel (72%), cobalt (93 %), uranium (66%), mica (almost 100%), gold and platinum.
The Lower Paleozoic era is relatively poor in large mineral deposits. The era gave oil shale, some oil deposits, phosphorites.
But in the Upper Paleozoic era, the largest resources of coal (50% of world reserves), oil, potassium and magnesium salts, polymetallic ores (lead and zinc), copper and large deposits of tungsten, mercury, asbestos, and phosphorites were formed.
In the Mesozoic era, the formation of the largest deposits of oil and coal, tungsten continues and new ones are formed - tin, molybdenum, antimony, diamonds.
Finally, the Cenozoic era gave the world the main reserves of bauxite, sulfur, boron, polymetallic ores, and silver. During this era, the accumulation of oil, copper, nickel and cobalt, molybdenum, antimony, tin, polymetallic ores, diamonds, phosphorites, potassium salts and other minerals continues.
V. I. Vernadsky, A. E. Fersman and other scientists identified the following types of areas of occurrence of minerals that naturally combine with each other: 1) geochemical belts. 2) geochemical fields; and 3) geochemical centers (nodes) of raw materials and fuel.
Several other terms are also used: metallogenic belts; shields and platforms; metallogenic provinces, roughly corresponding to the territorial units listed above
Metallogenic belts stretch for hundreds and thousands of kilometers. They border crystalline shields that have remained more or less unchanged since the earliest geological
epochs. Many important complexes of mineral deposits are associated with metallogenic belts.
The greatest ore belt of the globe encircles the Pacific Ocean. The length of the Pacific belt exceeds 30 thousand km. km. This belt consists of two zones - internal (facing the ocean) and external. The inner zone is more fully expressed on the American mainland and weaker on the Asian one, where it captures a chain of islands (Japanese, Taiwan, Philippines). Deposits of copper and gold are concentrated in the inner zone, and tin, polymetals (lead, zinc and other metals), antimony and bismuth are concentrated in the outer zone.
The Mediterranean ore belt includes the mountain ranges surrounding the Mediterranean Sea, and goes further through the Transcaucasus, Iran, North India to Malacca, where it connects with the Pacific belt. The length of the Mediterranean belt is about 16 thousand km.
The Ural belt is also one of the world's largest metallogenic belts.
A number of mountain systems are characterized by a regular distribution of minerals in the form of bands parallel to the axis of the mountain system. Thus, in many cases, very different combinations of ores are located at a relatively small distance from each other. The deepest formations (Cr, N1, P1, V, Ta, Nb) are predominantly located along the axis of the belts, and Sn, As are located on the sides of this axis. An,W; , even further - Cu, Zp, Pb, even further -Ag Co, finally Sb, Hg and other elements 6. Approximately such geographical distribution of chemical elements is observed in the Urals, whose minerals are grouped in five main bands: 1) western, with a predominance of sedimentary rocks: cuprous sandstones, oil, table and potassium-magnesium salts, coal; 2) central (axial), with heavy deep rocks: platinum, molybdenum, chromium, nickel; 3) metamorphic (deposits of copper pyrites); 4) eastern granite (iron ore, magnesites and rare metals) and 5) eastern sedimentary, with brown coal, bauxites.
Geochemical fields are located between the belts of folded mountain systems huge spaces crystalline shields and platforms covered by sedimentary rocks. These sedimentary rocks owe their origin to activities of the sea, rivers, winds, organic life, i.e. factors associated with exposure to solar energy.
Deposits of many minerals are associated with ancient crystalline rocks of vast expanses of shields and platforms: iron ores, gold, nickel, uranium, rare metals and some others. Usually flat terrain ancient shields and platforms, dense population and good provision of many of them with railways led to the fact that
deposits of shields and platforms of the globe (without the USSR) give approximately 2/3 of the extraction of iron ore, 3/4 of the extraction of gold and platinum, 9/10 of the extraction of uranium, nickel and cobalt, almost all of the extracted thorium, beryllium, niobium, zirconium, tantalum , a lot of manganese, chromium 7 .
In the placement of minerals of sedimentary rocks, the laws of ancient and modern climatic zonality are pro-, are. Most often, the zoning of past epochs affects the geography of sedimentary rocks. But modern zonal natural processes also significantly affect the formation and geographical distribution of various salts, peat and other minerals.
The patterns of distribution of ore and non-metallic minerals are determined by the tectonics of the country. Therefore, for an economic geographer, it is very important to know the tectonic map and the ability to read it and economically evaluate the features of the geological development of different tectonic regions of the country.
Thus, in most cases, the largest deposits of oil and natural gas. The marginal foredeeps of the platform, intermountain depressions, basins and arches connecting them, which arose when thick sedimentary rocks were crushed by hard blocks, attract the attention of search engines, since oil, natural gas, and salt deposits are often associated with them.
The so-called caustobioliths (combustible minerals) have their own patterns of geographical distribution, which do not coincide with the laws of the distribution of metals.
AT last years significant progress has been made in establishing the regularities of the geographical distribution of the oil-bearing regions of the globe. In the summary of OA Radchenko 8 four huge oil-bearing belts are distinguished: 1. Paleozoic (oil in it is almost exclusively confined to Paleozoic deposits); 2. Latitudinal Meso-Cenozoic; 3. Western Pacific Cenozoic and 4. Eastern Pacific Meso-Cenozoic.
According to 1960 data, 29% of world oil production was produced within the Paleozoic belt, 42.9% in the Latitude, 24.5% in the East Pacific, 2.8% in the Western Pacific, and 0.8% outside the belts 9 -
The main zones of coal accumulation are confined, as a rule, to marginal and internal troughs and to internal syneclises of ancient and stable platforms. For example, in the USSR the largest
7 See P. M. Tatarinov. Conditions for the formation of deposits of ore and non-metallic minerals. M., Gosgeoltekhizdat, 1955, pp. 268-269.
8 See O. A. Radchenko. Geochemical patterns of distribution of oil-bearing regions of the world. L., Nedra, 1965.
9 See ibid., p. 280.
coal basins are confined to the Donetsk trough of the Russian platform, to the Kuznetsk trough, etc.
The patterns of coal placement have not yet been fully established, but still some of the existing ones are interesting. So, according to G. F. Krasheninnikov, in the USSR 48% of coal reserves are confined to marginal and internal deflections, 43% to ancient stable platforms; in the USA, most of the coal reserves are located on stable platforms, and in Western Europe, almost all coal is confined to marginal and internal troughs. The largest coal basins are located in the depths of the continents; the great row belts (Pacific, Mediterranean and Ural) are relatively poor in coal.
Major mineral deposits
Among the many thousands of exploited deposits, relatively few, especially large and rich ones, are of decisive importance. The discovery of such deposits is very important for the development of the productive forces, and they strongly influence the location of industry and can noticeably change the economic profile of individual regions and even countries.
Carboniferous basins: Kansk-Achinsk, Kuznetsk, Pechora, Donetsk (USSR), Appalachian (USA);
Iron ore basins: Kursk magnetic anomaly, Krivoy Rog (USSR), Minas Gerais (Brazil), Lake Superior (USA), Labrador (Canada), North Swedish (Sweden); Oil-bearing regions: West Siberian, Volga-Ural, Mangyshlak (USSR), Marakaid (Venezuela), Middle East (Iraq, Iran, Kuwait, Saudi Arabia), Sahara (Algeria);
Manganese deposits: Nikopol, Chiatura (USSR), Franceville (Gabon); Nagpur-Balagatskoe (India).
Chromite deposits: South Ural (USSR), Great Dike (Southern Rhodesia), Guleman (Turkey), Trans-Vaal (South Africa);
Nickel deposits: Norilsk, Monchegorsko-Pechengskoe (USSR), Sudbury (Canada), Mayari-Barakonskoe (Cuba); Copper deposits: Katangsko-Zambian 10 (Congo with capital in Kinshasa and Zambia), with copper reserves of about 100 million tons, Udokan, Central Kazakhstan, South Ural DSSSR), Chuquicamata (Chile);
Deposits of polymetallic ores (lead, zinc, silver): Rudny Altai in the USSR, Pine Point (12.3 million tons). t zinc and lead) and Sullivan (more than 6 mln. t) in Canada, Broken Hill (more than 6 million t) in Australia. The world's largest source of silver (with production of about 500 t per year) - Coeur d "Alene - in the USA (Idaho).
10 The Katangese-Zambian copper belt is also very rich in cobalt.
Bauxite deposits (for aluminum production): Guinea (Republic of Guinea), with reserves of 1,500 million tons. t, Williamsfield (Jamaica), with reserves of 600 million tons. t, a number of deposits in Australia, with giant, still fairly unexplored deposits, the total size of which is estimated at 4,000 million tons. t.
Tin deposits: Malacca tin-bearing province (Burma, Thailand, Malaysia, Indonesia), with gigantic tin reserves of 3.8 million tons. t, and Columbia.
Gold deposits: Witwatersrand (South Africa), North-East of the USSR and Kyzylkum (USSR).
Phosphorite deposits: North African province (Morocco, Tunisia, Algeria), Khibiny massif (USSR).
Deposits of potash salts: Verkhnekamskoe and Pripyatskoe (USSR), Main Basin (GDR and FRG), Saskatchewan (Canada).
Diamond deposits: West Yakut (USSR), Kassai (Congo with its capital in Kinshasa).
Geological, geophysical and geochemical prospecting, the scope of which is increasingly increasing, lead and will lead in the future to the discovery of new unique mineral deposits. How great these discoveries can be, shows, for example, the fact of the establishment in 1950-1960. boundaries and reserves of the West Siberian oil and gas region with an area of 1770 thousand square meters of promising areas. km 2 , With high density of oil and gas reserves. In the next one and a half to two decades, Western Siberia will not only satisfy its needs with its own oil, but will also large quantities to supply oil and gas both to the European part of the USSR, and to Siberia and the countries of Western Europe.
Historical sequence of useresources of the earth's crust
In the course of their history, people gradually involved in the sphere of their production more and more chemical elements contained in the earth's crust, thus using more and more the natural basis for the development of productive forces.
V. I. Vernadsky divided the chemical elements according to the time of their beginning economic use man for a number of historical stages:
used in ancient times: nitrogen, iron, gold, potassium, calcium, oxygen, silicon, copper, lead, sodium, tin, mercury, silver, sulfur, antimony, carbon, chlorine;
added before the 18th century: arsenic, magnesium, bismuth, cobalt, boron, phosphorus;
added in the 19th century: barium, bromine, zinc, vanadium, tungsten, iridium, iodine, cadmium, lithium, manganese, molybdenum, osmium, palladium, radium, selenium, strontium, tantalum, fluorine, thorium, uranium, chromium, zirconium, rare earth;
added in the 20th century: all other chemical elements.
At present, all chemical elements of the periodic table are involved in the production. In the laboratory and in industrial settings, man has created, using laws of nature, such new elements (superhuranium), which are currently no longer in the thickness of the earth's crust.
In fact, now there is no element that would not have economic significance to one degree or another. However, the participation of chemical elements in production is far from being the same.
It is possible to subdivide chemical elements depending on their modern economic use into three groups 12:
elements of capital importance in industry and agriculture: hydrogen, carbon, nitrogen, oxygen, sodium, potassium, aluminum, magnesium, silicon, phosphorus, sulfur, chlorine, calcium, iron, uranium, thorium;
the main elements of modern industry: chromium, manganese, nickel, copper, zinc, silver, tin, antimony, tungsten, gold, mercury, lead, cobalt, molybdenum, vanadium, cadmium, niobium, titanium;
common elements of modern industry: boron, fluorine, arsenic, bromine, strontium, zirconium, barium, tantalum, etc.
During the last decades, the comparative economic importance of various chemical elements of the earth's crust has changed greatly. The development of a large-scale industry based on steam power has necessitated a massive increase in the extraction of coal and iron. The electrification of the economy led to a colossal increase in the demand for copper. The widespread use of internal combustion engines has caused a huge increase in oil production. The appearance of automobiles and an increase in the speed of their movement presented a demand for high-quality metal with an admixture of rare elements, and the aircraft industry needed first alloys of aluminum and magnesium with rare metals, and then, at modern speeds, titanium.
Finally, modern intra-nuclear energy has presented a huge demand for uranium, thorium and other radioactive elements and for lead, which is necessary for the construction of nuclear power plants.
Even in recent decades, the rate of growth in the extraction of various minerals has varied greatly, and it is difficult to predict which chemical elements will grow the most in the coming decades. In any case, the development of technology can lead to the fact that in certain periods the need for
11 See V. I. Vernadsky. I.chbr. cit., vol. 1. M., N.I. of the Academy of Sciences of the USSR. 195!, p. "112.
12 See A. E. Fersman. Geochemistry, vol. 4. L., 1939, p. 9 Some p. 726 were added.
which rare elements (necessary for modern "homeopathic metallurgy") 13 , non-ferrous metals, types of chemical raw materials will come into temporary conflict with their explored reserves. These contradictions will be resolved through the use of other, more common elements (change in industrial technology) and intensification of searches, in particular, at great depths.
Geochemical role of man
Man has now begun to play a very important geochemical role on Earth. As a rule, it first concentrates and then disperses chemical elements in the process of production and consumption. It produces a number of chemical compounds in a form in which they do not occur in nature, in the thickness of the earth's crust. Gets metallic aluminum and magnesium and other metals that are not found in nature in their native form. It creates new types of organic, silicon and organometallic compounds unknown in nature.
Man concentrated in his hands gold and a number of other precious metals and rare elements in quantities not found naturally in any one place. On the other hand, man extracts iron from powerful deposits, concentrates it, and then pulverizes over most of the land surface in the form of rails, roofing iron, wire, machines, metal products, etc. Man pulverizes even more. carbon (coal, oil, shale, peat) in the earth's crust, releasing it into a pipe in the full sense of the word, increasing the content of carbon dioxide in the air.
A. E. Fersman subdivided all chemical elements according to the nature of the relationship between natural and technological processes into six groups 14 , which can be combined into two large divisions:
BUT. consonant action nature and man.
Nature concentrates and man concentrates (platinum and platinum group metals).
Nature scatters and man scatters (boron, carbon, oxygen, fluorine, sodium, magnesium, silicon, phosphorus, sulfur, potassium, calcium, arsenic, strontium, barium).
3. "Nature concentrates, a person first concentrates in order to dissipate later (nitrogen and partially zinc).
B. Discordant action of nature and man. .
4. Nature concentrates, man scatters ( rare case: partly hydrogen, tin).
5. Nature scatters, man concentrates (helium, aluminum, zirconium, silver, gold, radium, thorium, uranium, neon, argon).
13 See E. M. Savitsky. rare metals. "Nature", 1956, No. 4.
14 See A. E. Fersman. Fav. works, vol. 3. M., Publishing House of the Academy of Sciences of the USSR, 1955, p. 726.
6. Nature scatters, man concentrates in order to dissipate later (lithium, titanium, vanadium, chromium, iron, cobalt, nickel, copper, selenium, bromine, niobium, manganese, cadmium, antimony, iodine, tantalum, tungsten, lead, bismuth) .
V. I. Vernadsky wrote 15 that man strives to make full use of the chemical energy of an element and therefore brings it into a state free from compounds (pure iron, metallic aluminum). “In a curious way,” V. I. Vernadsky continued, “here But thatsariens performs exactly the same work that in nature, in the weathering crust, is performed by microorganisms, as we know, which are here the source of the formation of native elements.
In recent years there has been an increasing tendency in technology to obtain superpure metals, so that man is increasingly acting in the direction noted by V. I. Vernadsky. Thus, man, using the natural resources of the earth's crust, acts as nature itself. However, if microorganisms release native elements in the course of their biological activity, then a person does the same with his production activity. Man, wrote V. I. Vernadsky, alone touched all chemical elements in his work, while in the vital activity of microorganisms there is an extraordinary specialization of individual species. Man increasingly began to regulate the geochemical work of microorganisms and is moving to practical use her.
In a very short time, compared with the geological history of the Earth, man has done colossal geochemical work.
The production activity of man is especially great in geochemical centers with a huge mining industry - in the coal basins, where, in addition to coal, other minerals are mined, in ore regions, etc.
Behind each person are many tons of annually mined ores of coal, building materials, oil and other minerals. At modern level production, humanity extracts from the bowels of about 100 billion cubic meters per year. t different rocks. By the end of our century, this figure will reach about 600 billion years. t.
A. E. Fersman wrote: “The economic and industrial activity of man has become comparable in scale and significance to the processes of nature itself. Substance and energy are not unlimited in comparison with the growing needs of man, their reserves in magnitude are of the same order as the needs of mankind: the natural geochemical laws of distribution and concentration of elements are comparable with the laws of technochemistry, i.e. with chemical transformations introduced by industry and the national economy. Man geochemically remakes the world” 16 .
15 See V. I. Vernadsky. Fav. cit., vol. 1, pp. 411-413.
16 A. E. F ersman. Selected works, vol. 3, p. 716.
Man goes deep into the bowels of the earth not only for minerals. In recent years, natural cavities formed in readily soluble rocks (limestone, gypsum, salts, etc.) have acquired great practical importance, which are used to house enterprises and warehouses in them. At first, only natural cavities were used for these purposes, but now work is being done to create artificial underground cavities by leaching easily soluble rocks where these cavities are needed and, of course, where they can be formed according to natural conditions (in the areas of shields they cannot be created; on the contrary, in areas with thick layers of sedimentary rocks, including limestones, salts, gypsum, there are favorable conditions for the artificial leaching of large cavities).
Economic use of the resources of the earth's crust
Minerals can be divided into several technical and economic groups, based on their economic purpose:
1) fuel (energy) group; 2) chemical group; 3) metallurgical group; 4) construction team.
The first group usually includes coal, oil, natural combustible gas, oil shale, peat. Now the same energy group of mineral raw materials should also include raw materials for extracting intranuclear energy - uranium and thorium.
All combustible minerals are at the same time, as a rule, the most valuable chemical raw materials. Using them only as fuel, mankind irrevocably destroys valuable modern chemical raw materials. The transition to intranuclear energy will make it possible in the future to use coal, oil, gas, peat, and shale mainly as chemical raw materials.
In 1965, there were 62 nuclear power plants (NPPs) operating all over the world with a total capacity of more than 8.5 million cubic meters. ket. They still generate an insignificant part of the electricity received in all countries, but the role of nuclear power plants will grow rapidly.
The proper chemical group of minerals includes salts (table salt, which is an important raw material for the soda industry, potassium salt for the production of mineral fertilizers, Glauber's salt, used in the soda industry, glass production, etc.), sulfur pyrites (for the production of sulfuric acid ), phosphorites and apatites (raw materials for superphosphate production and for phosphorus electric sublimation). An important raw material is deep water containing bromine, sub, helium and other elements necessary for the modern chemical industry.
The metallurgical group of minerals is very diverse. The most important of them is iron ore. The iron ore deposits of the globe are very different in terms of reserves, content, nature of impurities (harmful or foamy for
metallurgical industry). The world's largest iron ore deposit (mainly in the form of ferruginous quartzites) is located in the center of the European part of the USSR (Kursk magnetic anomaly). Iron has a number of "companions" that improve the properties of ferrous metal: titanium, manganese, chromium, nickel, cobalt, tungsten, molybdenum, vanadium and a number of other rare elements in the earth's crust. one *
The subgroup of non-ferrous metals includes copper, lead, zinc, bauxites, nephelines and alunites (raw materials for the production of alumina - aluminum oxide, from which metal aluminum is then obtained in electrolysis baths), magnesium salts and magnesites (raw materials for the production of magnesium metal), tin, antimony, mercury and some other metals.
A subgroup of noble metals - platinum, gold, silver - has great importance in engineering, especially in instrumentation. Gold and silver currently function as money.
The group of building materials is also diverse. Its importance is growing in connection with the rapid construction of buildings, bridges, roads, hydroelectric facilities and other structures. The area of the earth's surface covered with various building and road materials is increasing sharply. The most important building materials are marl, limestone, chalk (raw materials for the cement industry and building stone), clay and sand (raw materials for the silicate industry), igneous rocks (granite, basalt, tuff, etc.) used as building and road materials.
The degree of industrial concentration of the metal in the ore varies greatly over time, as it depends on the level of production technology.
In addition to absolute reserves and the degree of concentration of a particular chemical element, such a synthetic indicator as the coefficient of ore (coal) content, which shows the reserves of ore (coal) to the total volume of ore-bearing (coal-bearing) strata in percent, is of great importance for evaluating.
In addition, it is important for an economic geographer to know the depth of occurrence of minerals, the thickness, frequency and nature of the layers (sloping, steeply dipping, disturbed by faults), the presence of impurities that make it difficult or easier to enrich ores and coals, the degree of gas saturation, the abundance of groundwater and other aspects of natural resources. conditions of the thickness of the earth's crust, into which a person deepens with his mines and penetrates far from them with long adits diverging to the sides, or huge open-pit mines.
It is very favorable for industry when minerals can be mined in open pits - quarries. In particular, in the open coal mines of the USSR, cheap coal is mined in the coal basins of Karaganda, Kuzbass, Eki-
Bastuz, Kansk-Achinsk, Cheremkhovo basins and a number of other regions of the USSR.
Questions of the complex economic use of mineral resources are becoming more and more a field of economic geography, which must be closely connected with geochemistry and geology and make extensive use of their data.
A. E. Fersman assessed the commonwealth of geography and geochemistry as follows:
“As a result of the interaction of tectonic forces and the chains created by them, the influence of isostasy, seeking to balance the continental masses, the influence of water erosion, river systems and the general distribution of water and land, a whole cycle of phenomena is created that affect economic life, create reserves of hydropower, modify the laws of distribution of chemical elements and geographically direct the course of the country's development. According to Penk, they could be united by the term geographical factors, meaning by this word not only purely spatial relationships, but also their genetic connection, not only the morphology of objects, but also their dynamics and the very chemical essence, and if in recent years the concept of geography greatly expanded, covering the most diverse aspects of life and nature, and created the most important branch of this science - economic geography, then the introduction of the term geochemical geography is just as fair ... "17.
Extremely important is the economic-geographical, along with the geological and technological, study of areas of mineral resources. When carrying out geographical work in geochemical nodes, as A.E. Fersman wrote about this, it is necessary to determine:
the exact geographical location of the deposit area and its relationship with communication routes, railway points, large population centers;
general climatic conditions of the area (temperature and its fluctuations, precipitation, winds and their directions, etc.);
ascertaining the possibilities of transport and the most profitable directions both for the export of minerals and for communication with the central economic regions;
availability of labor force, opportunities for the economic development of these areas and for the organization of workers' settlements (and their supply);
issues of water supply both for the enterprise itself and for workers' settlements;
energy issues, availability of local sources of fuel or other types of energy; opportunity to connect with large lines power lines;
7) the availability of building and road materials necessary for the organization of workings and for residential and industrial construction.
The most important thing that an economic geographer can give is, together with technologists and economists, to determine and justify economically ways for the integrated use of fossil raw materials in certain geochemical belts, sections of geochemical fields, geochemical nodes, or usually combinations of both.
In capitalist countries, in metallogenic (ore, geochemical) belts and nodes that are complex in nature, only those minerals are extracted that bring maximum profit. The same "satellites" of the most valuable minerals, which today do not promise maximum profit, are dumped or released into the air (gases).
In a socialist society, new public relations, high technology and careful use of the earth's bowels allow the combined use of raw materials and fuel. “... The combined use of minerals is not an arithmetic addition of separate different industries - this is a technical and economic task of great importance, this is the economic and organizing principle of individual territories of the Union” 18, - wrote.A. E. Fersman.
Ore (geochemical) belts, zones and the richest areas of shields and platforms, and especially geochemical nodes, are in a number of cases the "cores" (bases) of the economic regions of different countries. At the same time, it must be emphasized that the productive forces of the mining economic regions cannot be regarded as a simple reflection ("cast") of their mineral complexes. Minerals are discovered and used in industry, usually not all at once, but gradually, in many cases for a long time, depending on certain economic requirements of society, from technology development, historical sequence settlement of the region, construction of communication lines, etc. First, some production links of the economic region arise on the basis of local raw materials and fuel, then others, and the history of the economic development of mining regions shows that in many capitalist countries the emergence of new links based on newly discovered minerals took place in a fierce struggle with the old branches of industry.
With the current level of development of the productive forces of socialist society, it is possible to give birth "from scratch" at once to a large production complex that uses not individual types of natural resources, but their complex combination. Examples are numerous in the eastern regions of the USSR.
A. E. F s r s m a n. Fav. works, vol. 2, p. 215.
A. E. F with r with m I and. Fav. works, vol. 2, p. 569.
The economic needs of the country and its individual regions lead to the fact that in the process of development of mining regions and centers, various bound friend on the other hand, industrial production relies not only on local, but also on imported mineral raw materials and fuel, since the requirements of the developing modern large-scale industrial production are wider than the natural combinations of minerals of the geochemical node richest in resources. There is a need to attract from outside the missing types of mineral raw materials and fuel, and the very concept of "missing" is associated primarily with the ways of developing the economy of a particular economic region.
When considering the problems of the integrated use of mineral raw materials and fuels of one or another geochemically integral territory, one must also bear in mind that the natural proportions of various minerals often do not meet the needs of society and hinder the development of individual industrial production. For the development of industry, in most cases, other economic (production) proportions of raw materials and fuel are needed. Of course, it is very favorable for the development of industry when, at one stage or another, economic needs are completely satisfied by the natural proportions of mineral raw materials and fuel. Otherwise, additional funds are needed to overcome the difficulties associated with the peculiarities of combinations of natural resources, in particular, for the delivery of missing resources from other geochemical belts and nodes.
As an example of the integrated use of fossil resources of the mining economic region, we can name the Donets Basin, where coal is mined, table salt, limestones, fire and acid resistant clays, mercury, quartz sand. However, these resources are not enough for the development of modern industrial Donbass. The following items are imported into the Donbass: iron ore from Krivoy Rog, Nikopol manganese and other “companions” of iron for the development of ferrous metallurgy. Cheap fuel from the Donbass is used to smelt zinc from imported zinc concentrate, while the off-gases and imported Ural pyrites serve as raw materials for the production of sulfuric acid. In turn, this acid is necessary for the production of mineral fertilizers based on coal coking waste and imported Kola apatite. The industrial Donbass has a certain economic structure of interconnected industries, a developing structure in which one link necessitates the emergence of others, more and more complex.
The complex use of mineral resources is inextricably linked with the issue of including low-grade (poor) types of fossil raw materials and fuel in production. It is far from always economically expedient to bring rich raw materials and
fuel; in very many cases it is more profitable to use poorer, but local raw materials and fuel. Of particular importance is the use of local fuel for electrification. V. I. Lenin in the “Outline of the plan of scientific and technical work” (April 1918) attached great importance to this: “The use of substandard grades of fuel (peat, coal of the worst grades) to obtain electrical energy with the lowest costs for the extraction and transportation of fuel” 19 .
Rich raw materials and first-class fuel are not always in the bowels where they are needed for production. Low-grade raw materials and substandard fuels can be found and used for the economy more or less everywhere, and long-distance expensive transportation of richer raw materials and fuels can be avoided. Substandard fuel can be very cheap, especially if its reserves are large and the fuel lies close to the surface (brown coal, shale) or on the surface (peat). Therefore, it is profitable to extract and use it at the place of extraction in the furnaces of power plants and for the production of chemical products, and to transmit electricity by wire to the centers of its large consumption. It should be especially noted that the development of the chemical industry makes it possible to turn many types of poor raw materials into rich ones when it finds valuable components in them.
Further, there are not always many rich sources of raw materials and fuel; it is necessary to look far ahead and draw into production even now low-grade sources of raw materials and fuel, in many cases very large in absolute reserves. Modern industry is a large consumer of minerals, and if it were based only on rich deposits, it would not be able to remain so large and increase its production. That is why the problem of using substandard grades of fuel and poor sources of raw materials is of great practical importance.
At the same time, of course, rich sources of raw materials and fuel are of great economic importance. At the present time, when there is an economic competition between the socialist countries and the capitalist countries, when the gain in time becomes great value, the widest possible use of primary, rich sources of raw materials and fuel is becoming very important. It is no coincidence that the plans for the development of the national economy of the USSR provide for the creation of new industrial centers and areas based on the richest deposits of raw materials and cheap fuel. Socialism brings its industry closer to the sources of raw materials and fuel, resolutely redistributing production geographically and thereby achieving a higher productivity of social labor. In centers of ore mining remote from the places of the main production, and other types of Poly. coll. cit., vol. 36, p.
It is difficult to count on the complex use of these raw materials. On the contrary, when industry, including manufacturing, is brought closer to the natural bases of raw materials and fuel, the possibilities for the integrated use of resources greatly increase.
The integrated use of all the mineral resources of the country (economic region) increases the overall productivity social labor, reduces the need for capital investments to achieve the planned volume of production, allows you to eliminate irrational transportation of raw materials and fuel.
The integrated use of the resources of the earth's interior in the socialist countries serves not only as an instrument for the comprehensive development of natural resources, but also as a correct distribution of productive forces throughout the country's territory, ensuring the fastest expanded socialist reproduction. A. E. Fersman correctly wrote: “The geography of industry is to a large extent the geography of the combined use of local raw materials ... A complex idea is an idea that is fundamentally economic, creating maximum values with the least expenditure of funds and energy, but this is an idea not only of today, it is the idea of protecting our natural resources from their predatory waste, the idea of using raw materials to the end, the idea of the possible preservation of our natural resources for the future" 20 .
Thus, the integrated use of raw materials and fuel is one of the laws of development of socialist industry. Science, having discovered this law and deeply developed it, must be able to apply it in practice, i.e., fight for the integrated use of the riches of the earth's crust and other natural resources, prove and ensure its economic expediency.
The distribution of mineral resources is subject to geological laws. Minerals of sedimentary origin are found within the sedimentary cover of platforms, in foothill and marginal troughs. Igneous minerals - in folded areas, places where the crystalline basement of ancient platforms comes to the surface (or close to the surface). Fuels are of sedimentary origin, form coal and oil and gas basins (the cover of ancient platforms, their internal and marginal troughs). The largest coal basins are located on the territory of Russia, the USA, Germany and other countries. Oil and gas are intensively produced in the Persian Gulf, the Gulf of Mexico, and Western Siberia.
Ore minerals include metal ores, they are confined to the foundations and shields of ancient platforms, and are also found in folded areas. Countries that stand out in terms of iron ore reserves are Russia, Brazil, Canada, the USA, Australia, and others. Often the presence of ore minerals determines the specialization of regions and countries.
Non-metallic minerals are widespread. These include: apatites, sulfur, potassium salts, limestones, dolomites, etc.
For economic development the most profitable are territorial combinations of minerals, which facilitate the complex processing of raw materials, the formation of large territorial production complexes. The rational use of resources is important - extracting the maximum possible amount of resources, more complete processing, integrated use of raw materials, etc.
Minerals have been formed throughout the history of the development of the earth's crust, as a result of endogenous and exogenous processes. The substances necessary for the formation of minerals come in magmatic melts, liquid and gaseous solutions from the upper mantle, the earth's crust, and the earth's surface.
Magmatogenic (endogenous) deposits are divided into several groups. So, when igneous melts penetrate into the earth's crust and cool, magmatic deposits are formed.
Ores of chromium, iron, titanium, nickel, copper, cobalt, platinum metal groups, etc. are associated with intrusions of basic composition; ores of phosphorus, tantalum, niobium, zirconium and rare earths are confined to alkaline massifs of igneous rocks. Deposits of mica, feldspars, precious stones, ores of beryllium, lithium, and cesium are genetically related to granite pegmatites. niobium, tantalum, part of tin, uranium and rare earths. Carbonatites associated with ultrabasic - alkaline rocks are an important type of deposits in which ores of iron, copper, niobium, tantalum, rare earths, as well as apatite and micas accumulate.
Minerals. Photo: Rodrigo Gomez Sanz
Sedimentary deposits are formed at the bottom of seas, lakes, rivers and swamps, forming stratified deposits in the sedimentary rocks that contain them. Placers containing valuable minerals (gold, platinum, diamonds, etc.) accumulate in coastal deposits of oceans and seas, as well as in river and lake deposits, and on valley slopes. The weathering deposits are associated with the ancient and modern weathering crust, which is characterized by infiltration deposits of ores of uranium, copper, native sulfur and residual deposits of nickel, iron, manganese, bauxite, magnesite, and kaolin.
In the setting high pressures and temperatures that prevail in deep interiors, pre-existing deposits are transformed with the appearance of metamorphogenic deposits (for example, iron ore of the Krivoy Rog basin and the Kursk magnetic anomaly, gold and uranium ores of South Africa) or are formed again in the process of metamorphism of rocks (deposits of marble, andalusite, kyanite, graphite, etc.).
Our country is rich in various minerals. Certain regularities can be traced in their distribution throughout the territory. Ores were formed mainly from magma and hot aqueous solutions released from it. Magma rose from the bowels of the Earth along faults and solidified in the thickness of rocks at various depths. Usually, the intrusion of magma occurred during periods of active tectonic movements, therefore, ore minerals are associated with folded areas of mountains. On the platform plains, they are confined to the lower tier - the folded foundation.
Different metals have different melting points. Consequently, the composition of ore accumulations also depends on the temperature of the magma that has intruded into the rock layers.
Large accumulations of ores are of industrial importance. They are called deposits.
Groups of closely spaced deposits of the same mineral are called mineral pools.
The richness of ores, their reserves and the depth of occurrence in different deposits are not the same. In the young mountains, many deposits are located under the thickness of sedimentary rocks crumpled into folds and it can be difficult to detect them.
With the destruction of mountains, accumulations of ore minerals are gradually exposed and are near the surface of the earth. It is easier and cheaper to get them here.
Deposits of iron ores (Western Sayan) and polymetallic ores (Eastern Transbaikalia), gold (highlands of Northern Transbaikalia), mercury (Altai), etc. are confined to the ancient folded regions.
The Urals are especially rich in various ore minerals, precious and semi-precious stones. There is a deposit of iron and copper, chromium and nickel, platinum and gold.
In the mountains northeastern Siberia and the Far East are concentrated deposits of tin and tungsten, gold, in the Caucasus - polymetallic ores.
Minerals platforms.
On platforms, ore deposits are confined to shields or to those parts of the plates where the thickness of the sedimentary cover is small and the foundation comes close to the surface. Iron ore basins are located here: the Kursk Magnetic Anomaly (KMA), the deposit of South Yakutia (Aldan Shield). On the Kola Peninsula there are deposits of apatite - the most important raw material for the production of phosphate fertilizers.
However, for platforms, fossils of sedimentary origin are most characteristic, concentrated in the rocks of the platform cover. Mostly these are non-metallic mineral resources. The leading role among them is played by fossil fuels: gas, coal, oil shale.
They were formed from the remains of plants and animals accumulated in the coastal parts of shallow seas and lacustrine-marsh land conditions. These abundant organic remains could accumulate only in sufficiently humid and warm conditions favorable for the increased development of vegetation.
The largest coal basins in Russia are:
- Tunguska, Lena, South Yakutsk (central Siberia)
- Kuznetsk, Kansk-Achinsk (in the marginal parts of the mountains of Southern Siberia)
- Pechorsky, Podmoskovny (on the Russian Plain)
Oil and gas fields are concentrated in the Ural part of the Russian Plain. From the Barents coast to the Caspian Sea, in Ciscaucasia.
But the largest oil reserves - in the bowels of the central part of Western Siberia - Samotlor and other gas - in its northern regions (Urengoy, Yamburg, etc.)
In hot dry conditions, salts accumulated in shallow seas and coastal lagoons. In the Cis-Urals, in the Caspian region and in the southern part of Western Siberia, there are large deposits of them.
Chapter X
IX 5. Time of formation of deposits
From the point of view of the sedimentary-migration theory of the origin of oil, the question of the time of formation of deposits can be solved on a geological basis using geochemical and physical parameters oil. Such data include: the age of host rocks, the time of formation of traps, the entry of host strata into the GZN, etc. It should be noted that the formation of a deposit is not a short-term process, but occurs over a long geological time (millions of years).
A deposit cannot be older than the strata in which it occurs. With the entry of sedimentary strata into the GZN, a mass migration of hydrocarbons from the source strata begins. This time interval is the most favorable for the formation of oil and gas accumulations. The deposit cannot be older than the trap in which it lies. Saturation pressure is also used to determine the age of the deposit. Gas cannot be released into the free phase until the saturation pressure is equal to the formation pressure. An oil deposit could not have formed at a pressure below the elasticity of the gases dissolved in it. Therefore, for oil deposits, saturation pressure can serve as a criterion for the depth and time of their initial formation. Calculations based on such initial data showed that the deposits of the Samara Volga and Trans-Volga regions, occurring in the Devonian deposits, were formed in the Carboniferous, or in the Early Permian, i.e. 250-300 million years ago.
Accumulations of oil and gas are known in sediments of all ages, from the Proterozoic to the Quaternary. However, their main reserves are confined to sedimentary rocks of a certain age, while in rocks of other ages they are present only in small amounts. Experience shows that the same deposits are highly productive in some areas and not productive in others. From the point of view of the sedimentary-migration theory of the origin of oil, such an uneven distribution of deposits is explained by the lithofacies conditions for the formation of host strata and features tectonic structure and development of a particular region and district.
The main part of the world's proven oil reserves is concentrated in the Paleozoic and Mesozoic deposits, and the main part of the gas reserves - in the Cretaceous and Cenozoic deposits (Fig. 10). In Precambrian and Quaternary sediments, accumulations of oil and gas are very rare and on a small scale.
According to A.Ya. Krems, in 1954 in the world oil was extracted from Paleozoic deposits - 33%, Mesozoic deposits - 19%, Cenozoic deposits - 45%. In 1965, in the USSR, gas was extracted from the Cenozoic - 21%, Mesozoic - 40%, Paleozoic - 39%; oil from the Cenozoic - 8.5%, Mesozoic - 7.5%, Paleozoic - 74%. With the introduction of Western Siberian fields into development in the 1960s, these ratios have undergone significant changes. Now oil and gas in Russia is mainly extracted from the deposits of the Mesozoic group.
Each continent and each oil and gas basin has its own regularities in the distribution of oil and gas reserves over stratigraphic complexes. Moreover, the main reserves are confined to large and giant deposits.
The uneven distribution of oil and gas reserves along the stratigraphic section is explained by the periodicity (cyclicity) of geological processes, namely, the cyclicity of accumulation processes organic matter in sedimentary strata. Those deposits where the maximum oil and gas reserves are concentrated contain the maximum volumes of stone and brown coal. This indicates that the oil and gas bearing strata were formed during the heyday of organic world, during periods of thalassocratic modes of development of the continents, when a significant part of them was covered with relatively shallow seas, in which there was a rapid development of micro- and microorganisms. Such regimes dominated in the Devonian, Carboniferous, in the Jurassic and Cretaceous periods, in the Zocene, Oligocene and Miocene. In the Triassic deposits, the formation of which took place under the conditions of the geocratic regime of the continents, when the continents were uplifted and mostly represented land, oil and gas bearing strata practically did not form. They contain minimum stocks oil and gas.
X.2. Patterns of distribution of oil and gas by area. Oil and gas provinces (basins)
Oil and gas bearing territories occupy only about 30% of the surface of the continents, the rest of the territory does not contain oil and gas accumulations. Oil and gas containing strata are absent on the shields of ancient platforms and within mountain systems composed of geosynclinal folded metamorphosed formations. On the continents, plains and lowlands located between mountain systems and shields are oil and gas bearing. Within them, the sedimentary strata lie on a folded base, are metamorphosed very weakly or not metamorphosed at all, deformed into flat platform-type folds. However, oil and gas deposits are formed only in sedimentary basins with a platform cover thickness of at least 1.5-2.0 km. Only such pools have a sufficient volume of dispersed matter to convert them into liquid and gaseous hydrocarbons on an industrial scale.
Oil and gas provinces (basins) are understood as large areas long-term dives made by weakly metamorphosed sedimentary strata and containing oil and gas deposits. Currently, about 160 oil and gas bearing basins are known on the continents and islands of the globe, which differ from each other in their size, age of sedimentary strata, their association with large tectonic elements of the earth's crust, and other indicators.
