In the second half of the 20th century, the world became sick with ultra-deep drilling. In the United States, a new program for studying the ocean floor (Deep Sea Drilling Project) was being prepared. Built specifically for this project, the Glomar Challenger vessel spent several years in the waters of various oceans and seas, drilling almost 800 wells in their bottom, reaching a maximum depth of 760 m. By the mid-1980s, the results of offshore drilling confirmed the theory of plate tectonics. Geology as a science was born again. Meanwhile, Russia went its own way. Interest in the problem, awakened by the success of the United States, resulted in the program "Study of the bowels of the Earth and ultra-deep drilling", but not in the ocean, but on the continent. Despite centuries of history, continental drilling seemed to be a completely new thing. After all, it was about previously unattainable depths - more than 7 kilometers. In 1962, Nikita Khrushchev approved this program, although he was guided by political motives rather than scientific ones. He did not want to lag behind the United States.
The well-known oilman, Doctor of Technical Sciences Nikolay Timofeev, headed the newly created laboratory at the Institute of Drilling Technology. He was instructed to substantiate the possibility of ultra-deep drilling in crystalline rocks - granites and gneisses. The research took 4 years, and in 1966 the experts issued a verdict - it is possible to drill, and not necessarily with the technology of tomorrow, the equipment that is already there is enough. The main problem is the heat at depth. According to calculations, as it penetrates into the rocks that make up the earth's crust, the temperature should increase by 1 degree every 33 meters. This means that at a depth of 10 km we should expect about 300°C, and at 15 km - almost 500°C. Drilling tools and devices will not withstand such heating. It was necessary to look for a place where the bowels are not so hot ...
Such a place was found - an ancient crystalline shield of the Kola Peninsula. The report, prepared at the Institute of Physics of the Earth, said: over the billions of years of its existence, the Kola shield has cooled down, the temperature at a depth of 15 km does not exceed 150 ° C. And geophysicists have prepared an approximate section of the bowels of the Kola Peninsula. According to them, the first 7 kilometers are granite strata of the upper part of the earth's crust, then the basalt layer begins. Then the idea of a two-layer structure of the earth's crust was generally accepted. But as it turned out later, both physicists and geophysicists were wrong. The drilling site was chosen on the northern tip of the Kola Peninsula near Lake Vilgiskoddeoaivinjärvi. In Finnish, it means "Under the wolf mountain", although there is no mountain or wolves in that place. Drilling of the well, the design depth of which was 15 kilometers, began in May 1970.
But
From here you can listen to hellish sounds from the well.
Film: Kola Superdeep: Last Salute
Ultra deep drilling
According to the existing classification, wells with a depth of 3,000-6,000 m are classified as deep, and wells with a depth of 6,000 m or more are classified as ultra-deep.
In 1958, the Mohol ultra-deep drilling program appeared in the United States. This is one of the most daring and mysterious projects of post-war America. Like many other programs, Mohol was designed to overtake the USSR in scientific rivalry by setting a world record in ultra-deep drilling. The name of the project comes from the words "Mohorovicic" - the name of a Croatian scientist who identified the interface between the earth's crust and mantle - the Moho border, and "hole", which in English means "well". The creators of the program decided to drill in the ocean, where, according to geophysicists, the earth's crust is much thinner than on the continents. It was necessary to lower the pipes several kilometers into the water, go 5 kilometers of the ocean floor and reach the upper mantle.
In April 1961, off the island of Guadeloupe in the Caribbean Sea, where the water column reaches 3.5 km, geologists drilled five wells, the deepest of which entered the bottom at 183 meters. According to preliminary calculations, in this place, under sedimentary rocks, they expected to meet the upper layer of the earth's crust - granite. But the core lifted from under the sediments contained pure basalts - a kind of antipode of granites. The result of drilling discouraged and at the same time inspired scientists, they began to prepare a new phase of drilling. But when the cost of the project exceeded $100 million, the US Congress stopped funding. "Mohol" did not answer any of the questions posed, but it showed the main thing - ultra-deep drilling in the ocean is possible.
Since then, the world has become ill with ultra-deep drilling. In the United States, a new program for studying the ocean floor (Deep Sea Drilling Project) was being prepared. Built specifically for this project, the Glomar Challenger vessel spent several years in the waters of various oceans and seas, drilling almost 800 wells in their bottom, reaching a maximum depth of 760 m. By the mid-1980s, the results of offshore drilling confirmed the theory of plate tectonics. Geology as a science was born again. Meanwhile, Russia went its own way. Interest in the problem, awakened by the success of the United States, resulted in the program "Study of the bowels of the Earth and ultra-deep drilling", but not in the ocean, but on the continent. Despite centuries of history, continental drilling seemed to be a completely new thing. After all, it was about previously unattainable depths - more than 7 kilometers. In 1962, Nikita Khrushchev approved this program, although he was guided by political motives rather than scientific ones. He did not want to lag behind the United States.
The well-known oilman, Doctor of Technical Sciences Nikolay Timofeev, headed the newly created laboratory at the Institute of Drilling Technology. He was instructed to substantiate the possibility of ultra-deep drilling in crystalline rocks - granites and gneisses. The research took 4 years, and in 1966 the experts issued a verdict - it is possible to drill, and not necessarily with the technology of tomorrow, the equipment that is already there is enough. The main problem is the heat at depth. According to calculations, as it penetrates into the rocks that make up the earth's crust, the temperature should increase by 1 degree every 33 meters. This means that at a depth of 10 km we should expect about 300°C, and at 15 km - almost 500°C. Drilling tools and devices will not withstand such heating. It was necessary to look for a place where the bowels are not so hot ...
Such a place was found - an ancient crystalline shield of the Kola Peninsula. The report, prepared at the Institute of Physics of the Earth, said: over the billions of years of its existence, the Kola shield has cooled down, the temperature at a depth of 15 km does not exceed 150 ° C. And geophysicists have prepared an approximate section of the bowels of the Kola Peninsula. According to them, the first 7 kilometers are granite strata of the upper part of the earth's crust, then the basalt layer begins. Then the idea of a two-layer structure of the earth's crust was generally accepted. But as it turned out later, both physicists and geophysicists were wrong. The drilling site was chosen on the northern tip of the Kola Peninsula near Lake Vilgiskoddeoaivinjärvi. In Finnish, it means "Under the wolf mountain", although there is no mountain or wolves in that place. Drilling of the well, the design depth of which was 15 kilometers, began in May 1970. The drilling of the Kola well SG-3 did not require the creation of fundamentally new devices and giant machines. We started working with what we already had: the Uralmash 4E unit with a lifting capacity of 200 tons and light-alloy pipes. What was really needed at that time was non-standard technological solutions. Indeed, in solid crystalline rocks no one has drilled to such a great depth, and what will be there, they imagined only in general terms. Experienced drillers, however, understood that no matter how detailed the project was, the real well would be much more complicated. After 5 years, when the depth of the SG-3 well exceeded 7 kilometers, a new drilling rig "Uralmash 15,000" was installed - one of the most modern at that time. Powerful, reliable, with an automatic tripping mechanism, it could withstand a pipe string up to 15 km long. The drilling rig has turned into a fully sheathed tower 68 m high, recalcitrant to the strong winds raging in the Arctic. A mini-factory, scientific laboratories and a core storage facility have grown up nearby. When drilling to shallow depths, a motor that rotates a string of pipes with a drill at the end is installed on the surface. The drill is an iron cylinder with teeth made of diamonds or hard alloys - a crown. This crown bites into the rocks and cuts out of them a thin column - core. To cool the tool and remove small debris from the well, drilling fluid is injected into it - liquid clay, which circulates all the time through the wellbore, like blood in vessels. After some time, the pipes are raised to the surface, freed from the core, the crown is changed and the column is lowered into the bottomhole again. This is how normal drilling works. And if the barrel length is 10-12 kilometers with a diameter of 215 millimeters? The string of pipes becomes the thinnest thread lowered into the well. How to manage it? How to see what is happening in the face? Therefore, at the Kola well, miniature turbines were installed at the bottom of the drill string, they were launched by drilling fluid injected through pipes under pressure. The turbines rotated the carbide bit and cut out the core. The whole technology was well developed, the operator on the control panel saw the rotation of the crown, knew its speed and could control the process. Every 8-10 meters, a multi-kilometer column of pipes had to be lifted up. The descent and ascent took a total of 18 hours. 7 kilometers - the mark for the Kola superdeep fatal. Behind it began the unknown, many accidents and a continuous struggle with rocks. The barrel could not be kept upright. When 12 km were covered for the first time, the well deviated from the vertical by 21°. Although the drillers had already learned to work with the incredible curvature of the trunk, it was impossible to go any further. The well had to be re-drilled from the mark of 7 kilometers. To get a vertical hole in hard formations, you need a very rigid bottom of the drill string so that it enters the subsoil like butter. But another problem arises - the well is gradually expanding, the drill dangles in it, as in a glass, the walls of the barrel begin to collapse and can crush the tool. The solution to this problem turned out to be original - the pendulum technology was applied. The drill was artificially swung in the well and suppressed strong vibrations. Due to this, the trunk turned out vertical.
The most common accident on any drilling rig is a pipe string break. Usually the pipes try to seize again, but if this happens at a great depth, then the problem becomes unrecoverable. It is useless to look for a tool in a 10-kilometer well, they threw such a hole and started a new one, a little higher. Breakage and loss of pipes on SG-3 happened many times. As a result, in its lower part, the well looks like the root system of a giant plant. The branching of the well upset the drillers, but turned out to be happiness for geologists, who unexpectedly received a three-dimensional picture of an impressive segment of ancient Archean rocks that formed more than 2.5 billion years ago.
In June 1990, SG-3 reached a depth of 12,262 m. They began to prepare the well for drilling up to 14 km, and then an accident occurred again - at the level of 8,550 m, the pipe string broke. The continuation of the work required a long preparation, updating equipment and new costs. In 1994, drilling of the Kola Superdeep was stopped. After 3 years, she got into the Guinness Book of Records and still remains unsurpassed. Now the well is a laboratory for studying deep bowels. SG-3 was a secret facility from the very beginning. Both the border zone, and strategic deposits in the district, and scientific priority are to blame. The first foreigner to visit the rig was one of the leaders of the Academy of Sciences of Czechoslovakia. Later, in 1975, an article about the Kola Superdeep was published in Pravda signed by the Minister of Geology Alexander Sidorenko. There were still no scientific publications on the Kola well, but some information leaked abroad. The world began to learn more from rumors - the deepest well is being drilled in the USSR.
The veil of secrecy, probably, would have hung over the well until the very “perestroika” had it not been for the World Geological Congress in Moscow in 1984. Carefully prepared for such a major event in the scientific world, a new building was even built for the Ministry of Geology - many participants were expecting it. But foreign colleagues were primarily interested in the Kola Superdeep! The Americans did not believe that we had it at all. The depth of the well by that time had reached 12,066 meters. There was no point in hiding the object anymore. In Moscow, the congress participants were treated to an exhibition of achievements in Russian geology, one of the stands was dedicated to the SG-3 well. Experts from all over the world looked in bewilderment at an ordinary drill head with worn carbide teeth. And this is how they drill the deepest well in the world? Incredible! A large delegation of geologists and journalists went to the village of Zapolyarny. Visitors were shown the drilling rig in action, and 33-meter pipe sections were taken out and disconnected. There were heaps of exactly the same drilling heads around, like the one that lay on the stand in Moscow.
From the Academy of Sciences, the delegation was received by a well-known geologist, Academician Vladimir Belousov. During a press conference from the audience, he was asked a question:
- What is the most important thing shown by the Kola well?
- Lord! The main thing is that it showed that we know nothing about the continental crust, - the scientist answered honestly.
Of course, they knew something about the earth's crust of the continents. The fact that the continents are composed of very ancient rocks, aged from 1.5 to 3 billion years, was not refuted even by the Kola well. However, the geological section compiled on the basis of the SG-3 core turned out to be exactly the opposite of what scientists imagined earlier. The first 7 kilometers were composed of volcanic and sedimentary rocks: tuffs, basalts, breccias, sandstones, dolomites. Deeper lay the so-called Conrad section, after which the velocity of seismic waves in the rocks increased sharply, which was interpreted as the boundary between granites and basalts. This section was passed long ago, but the basalts of the lower layer of the earth's crust did not appear anywhere. On the contrary, granites and gneisses began.
The section of the Kola well refuted the two-layer model of the earth's crust and showed that the seismic sections in the bowels are not the boundaries of layers of rocks of different composition. Rather, they indicate a change in the properties of the stone with depth. At high pressure and temperature, the properties of rocks, apparently, can change dramatically, so that granites in their physical characteristics become similar to basalts, and vice versa. But the “basalt” raised to the surface from a depth of 12 km immediately became granite, although it experienced a severe attack of “caisson disease” along the way - the core crumbled and disintegrated into flat plaques. The further the well went, the fewer quality samples fell into the hands of scientists. The depth contained many surprises. It used to be natural to think that with distance from the earth's surface, with increasing pressure, rocks become more monolithic, with a small number of cracks and pores. SG-3 convinced scientists otherwise. Starting from 9 kilometers, the strata turned out to be very porous and literally crammed with cracks through which aqueous solutions circulated. Later, this fact was confirmed by other ultra-deep wells on the continents. At depth it turned out to be much hotter than expected: by as much as 80 °! At the mark of 7 km the temperature in the face was 120°C, at 12 km it reached 230°C. In the samples of the Kola well, scientists discovered gold mineralization. Inclusions of the precious metal were found in ancient rocks at a depth of 9.5-10.5 km. However, the concentration of gold was too low to declare a deposit - an average of 37.7 mg per ton of rock, but sufficient to expect it in other similar places. The demonstration of the Kola well in 1984 made a deep impression on the world community. Many countries have begun to prepare projects for scientific drilling on the continents. Such a program was approved in Germany in the late 1980s. The ultra-deep well KTB Hauptborung was drilled from 1990 to 1994, according to the plan, it was supposed to reach a depth of 12 km, but due to unpredictably high temperatures, it was only possible to reach the mark of 9.1 km. Thanks to the openness of data on drilling and scientific work, good technology and documentation, the KTV ultra-deep well remains one of the most famous in the world.
The location for drilling this well was chosen in the southeast of Bavaria, on the remains of an ancient mountain range, whose age is estimated at 300 million years. Geologists believed that somewhere here there is a zone of connection of two plates, which were once the shores of the ocean. According to scientists, over time, the upper part of the mountains was erased, exposing the remains of the ancient oceanic crust. Even deeper, ten kilometers from the surface, geophysicists discovered a large body with an abnormally high electrical conductivity. Its nature was also hoped to be clarified with the help of a well. But the main task was to reach a depth of 10 km in order to gain experience in ultra-deep drilling. Having studied the materials of the Kola SG-3, the German drillers decided to first go through a test well 4 km deep in order to get a more accurate idea of the working conditions in the bowels, test the equipment and take a core. At the end of the pilot work, much of the drilling and scientific equipment had to be redone, something to be created anew.
The main - ultra-deep - well KTV Hauptborung was laid just two hundred meters from the first one. For the work, they built an 83-meter tower and created the most powerful drilling rig at that time with a lifting capacity of 800 tons. Many drilling operations have been automated, primarily the mechanism for lowering and retrieving a pipe string. A self-guided vertical drilling system made it possible to make an almost sheer shaft. Theoretically, with such equipment it was possible to drill to a depth of 12 kilometers. But the reality, as always, turned out to be more complicated, and the plans of scientists did not come true.
Problems at the KTV well began after a depth of 7 km, repeating much of the fate of the Kola Superdeep. At first, it is believed that due to the high temperature, the vertical drilling system broke down and the shaft went sideways. At the end of the work, the bottomhole deviated from the vertical by 300 m. Then, more complicated accidents began - a break in the drill string. As well as on Kolskaya, new shafts had to be drilled. The narrowing of the well caused certain difficulties - at the top its diameter was 71 cm, at the bottom - 16.5 cm.
It cannot be said that the scientific results of the KTV Hauptborung captured the imagination of scientists. At depth, amphibolites and gneisses, ancient metamorphic rocks, were mainly deposited. The zone of convergence of the ocean and the remains of the oceanic crust were not found anywhere. Perhaps they are in another place, there is also a small crystalline massif, uplifted to a height of 10 km. A graphite deposit was discovered a kilometer from the surface.
In 1996, the KTV well, which cost the German budget $338 million, came under the patronage of the Research Center for Geology in Potsdam, and it was turned into a laboratory for deep subsurface observations and a tourist attraction.
Currently, 2 wells have been drilled, which have surpassed the Kola well in terms of the length of the wellbore. These are OR-I (Odoptu field, Sakhalin, Russia) - 12,345 m, Maersk Oil BD-04A (Qatar) - 12,290 m.
The deepest oil deposit in our country was discovered in the area of Grozny (Chechen Republic) at a depth of 5300 m, and industrial gas flow was obtained in the Caspian depression from a depth of 5370 km. Abroad, the largest depth from which gas is produced is 7460 m (USA, Texas).
Udmurtia also has its own “super-deep” well. This is a parametric well drilled in 19991 in the Sarapul region, its depth is 5500 m.
All ultra-deep wells have a telescopic design: drilling starts with the largest diameter, and then moves on to smaller ones. Thus, in the Kola well (Russia), the diameter decreased from 92 cm in the upper part to 21.5 cm at a depth of 12,262 m. And in the KTB-Oberpfalz well (Germany), from 71 cm to 16.5 cm at a depth of 7,500 m. The mechanical speed of drilling ultra-deep wells is 1-3 m/hour. It is possible to go deep by 6-10 m in one run between round-trip operations. The average speed of lifting a drill string is 0.3-0.5 m/s In general, drilling one ultra-deep well takes years. The practice of drilling wells in difficult geological conditions, scientific developments in the field of drilling and casing, carried out in recent years, have made it possible to increase the depth of wells (up to 7,000 m or more) and improve their design in the following areas: , the use of bits of reduced and small diameters; the use of the method of sectional running of casing strings and the fastening of wellbores with intermediate liner strings; the use of casing pipes with welded connecting elements and sleeveless casing pipes with special threads when assembling intermediate and, in some cases, production strings; reducing the final diameter of wells and production columns.
Ultra-deep drilling is based on the technology of rotary drilling and sequential fixation of the passed intervals with casing strings. Characteristic features of technology: *increase with depth of temperature and hydrostatic pressure; "loss of stability of rocks under the influence of the difference between rock and hydrostatic pressures; "an increase in the mass of the drill and casing strings; "deceleration of the rate of deepening due to an increase in the time of descent / retrieval of the drill string and deterioration of the drillability of rocks; "an increase in energy losses during the transfer of force effects from the surface to the bottom; "the need to take cores in large volumes and conduct downhole geophysical surveys.
For ultra-deep drilling, drilling rigs with a lifting capacity of up to 11 MN (1100 tons) with a total capacity of up to 18 thousand kW with pumps (2-4 units) for an operating pressure of 40-50 MPa with a capacity of up to 1,600 kW each have been created and are being used. As a rule, such installations are electrically driven from a direct current source, which allows for stepless regulation of the operation of the main mechanisms. The descent / retrieval of the drill string is carried out mainly with elongated "candles" up to 37 m with maximum mechanization and automation of the process. Installations of this type are produced by such domestic manufacturers as the Ural Heavy Machine Building Plant (UZTM) and the Volgograd Drilling Equipment Plant (VZBT).
The division of drilling rigs into deep and ultra-deep drilling rigs is determined by many factors:
1) technical characteristics of the installation; hook load, pressure and delivery of drilling pumps, type and power of the main drive; 2) the mass of ground equipment (as a consequence of the technical characteristics of the drilling rig); 3) .way of installation, dismantling and transportation; 4) the time spent building the drilling rig; 5) well drilling time; 6) organization of drilling operations.
In ultra-deep drilling, a rotary or turbine drilling method is used, both are possible with interval alternation. The first of them has found wide distribution in the West, the second - in Russia. The turbine method makes it possible to successfully use drill rods made of light (heat-resistant, aluminum) alloys (LBT). According to the criterion of allowable stresses in pipes, the turbine method in combination with LBT makes it possible to increase the drilling depth by 1.5-2 times compared to the rotary method in combination with steel pipes (SBT) at the same load capacity. This advantage is confirmed by the practice of drilling the Kola well: when drilling it, a composite string of LBT (bottom) and SBT (top), approximately 2,000 m, was used, using aluminum alloys, which were 2.4 times lighter than steel. The general trend of oil and gas production from ever deeper horizons can be illustrated by the following figures. Even 20 years ago, the main oil production (66%) was carried out from the youngest Cenozoic rocks. 19% of oil was extracted from older Mesozoic rocks, and 15% from the most ancient Paleozoic rocks. Now the situation has changed: Mesozoic rocks have become the main suppliers of oil, followed by Paleozoic rocks.
Prevention of superdeep wells curvature is an important condition for their successful drilling. To maintain the forces of resistance to the movement of the drill string and the wear of the casing strings within acceptable limits, it is sought that the intensity of the curvature does not exceed 2-3° per 1 km, while maintaining the constancy of the azimuth of the curvature, and the absolute value of the zenith angle does not exceed 10-12°. Particularly stringent requirements are imposed on the verticality of the upper part of the trunk. To combat curvature, rigid bottomhole assembly (BHA) with full-size centralizers is usually used, and in the absence of the desired effect, pendulum-type BHA. In the upper part of the wells (up to 3-4 km), jet-turbine drills are successfully used when drilling a large diameter borehole.
The development of ultra-deep drilling in the foreseeable future is likely to be based on rotary drilling technology. As the depth increases (more than 10 km), the downhole bit drive will replace the rotary method, opening the way for realizing the fundamental advantages of drill pipes made of light metal alloys based on aluminum and titanium. The focus is likely to be on the heat-resistant geared turbodrill.
There are plans to drill a 20-kilometer well from the bottom of the Pacific Ocean.
It is not for nothing that ultra-deep drilling is compared with the conquest of space. Such programs, on a global scale, absorbing all the best that humanity currently has, give impetus to the development of many industries, technology, and ultimately pave the way for a new breakthrough in science. Table 23 provides information about deepest wells in the world, Figure 36 shows the location superdeep wells on the territory of the former USSR.
Table 23. The deepest wells in the world
| Well name | Location | Drilling time | Drilling depth, m | Purpose of drilling | |
| Design | Actual | ||||
| Aralsor SG-1 | Caspian lowland | 1962 -1971 | 6 800 | Search for oil and gas | |
| Biikzhalskaya SG-2 | Caspian lowland | 1962 -1971 | 6 200 | Search for oil and gas | |
| Kola SG-3 | Kola Peninsula | 1970 -1992 | 15 000 | 12 262 | scientific drilling |
| Saatlinskaya | Azerbaijan | 1977 -1990 | 11 500 | 8 324 | Search for oil and gas |
| Kolvinskaya | Arhangelsk region | 7 057 | |||
| Muruntauskaya SG-10 | Uzbekistan | 7 000 | 3 000 | Search for gold | |
| Timan-Pechora SG-5 | Northeast Russia | 1984 -1993 | 7 000 | 6 904 | |
| Tyumenskaya SG-6 | Western Siberia | 1987 -1996 | 8 000 | 7 502 | Search for oil and gas |
| Novo-Elkhovskaya | Tatarstan | 5 881 | |||
| Vorotilovskaya | Volga region | 1989 -1992 | 5 374 | Search for diamonds, study of the Puchezh-Katunkka astrobleme. | |
| Krivorozhskaya SG-8 | Ukraine | 1984-1993 | 12 000 | 5 382 | Search for ferruginous quartzites |
| Ural SG-4 | Middle Ural | 15 000 | 6 100 | Search for copper ores, Studying the structure of the Urals | |
| En-Yakhtinskaya SG-7 | Western Siberia | 7 500 | 6 900 | Search for oil and gas | |
| Sarapulskaya Parametric | Udmurtia | 5 500 | 5 500 | scientific drilling | |
| University | USA | 70s of the twentieth century | 8 686 | Search for oil and gas | |
| baden unit | USA | 9 159 | Search for oil and gas | ||
| Bertha Rogers | USA | 9 583 | Search for oil and gas | ||
| Zisterdorf | Austria | 8 553 | Search for oil and gas | ||
| Silyan Ring | Sweden | 6 800 | Search for oil and gas | ||
| Bighorn | USA, Wyoming | 1980s | 7 583 | scientific drilling | |
| KTV Hauptbohrung | Germany | 1990-1994 | 12 000 | 9 101 | scientific drilling |
| Mirow-1 | Germany | 1974-1979 | Search for oil and gas | ||
| Maersk Oil BD-04A | Qatar | 12 290 | Search for oil and gas | ||
| OP-I | Sakhalin, Russia | 12 345 | 12 345 | Search for oil and gas |
Rice. 36. Map of the location of deep and ultra-deep wells in Russia
Hundreds of thousands of wells have been drilled in the earth's crust over the last decades of the last century. And this is not surprising, because the search and extraction of minerals in our time is inevitably associated with deep drilling. But among all these wells there is only one on the planet - the legendary Kola Superdeep (SG), the depth of which is still unsurpassed - more than twelve kilometers. In addition, the SG is one of the few that was drilled not for the sake of exploration or mining, but for purely scientific purposes: to study the most ancient rocks of our planet and learn the secrets of the processes going on in them.
Today, no drilling is carried out at the Kola Superdeep, it was stopped in 1992. SG was not the first and not the only one in the program of studying the deep structure of the Earth. Of the foreign wells, three reached depths of 9.1 to 9.6 km. It was planned that one of them (in Germany) would surpass the Kola. However, drilling on all three, as well as on the SG, was stopped due to accidents and for technical reasons cannot be continued yet.
It can be seen that it is not in vain that the tasks of drilling ultra-deep wells are compared in complexity with a flight into space, with a long-term space expedition to another planet. Rock samples extracted from the earth's interior are no less interesting than samples of lunar soil. The soil delivered by the Soviet lunar rover was studied at various institutes, including the Kola Science Center. It turned out that the composition of the lunar soil almost completely corresponds to the rocks extracted from the Kola well from a depth of about 3 km.
SITE SELECTION AND FORECAST
A special exploration expedition (Kola GRE) was created to drill the SG. The place of drilling was also, of course, not chosen by chance - the Baltic Shield in the area of the Kola Peninsula. Here, the oldest igneous rocks with an age of about 3 billion years come to the surface (and the Earth is only 4.5 billion years old). It was interesting to drill in the most ancient igneous rocks, because the sedimentary rocks to a depth of 8 km have already been well studied in oil production. And in igneous rocks during mining, they usually get only 1-2 km. The choice of a place for the SG was also facilitated by the fact that the Pecheneg trough is located here - a huge bowl-like structure, as if pressed into ancient rocks. Its origin is associated with a deep fault. And it is here that large copper-nickel deposits are located. And the tasks assigned to the Kola geological expedition included identifying a number of features of geological processes and phenomena, including ore formation, determining the nature of the boundaries separating layers in the continental crust, and collecting data on the material composition and physical state of rocks.
Prior to drilling, a section of the earth's crust was built on the basis of seismological data. It served as a forecast for the appearance of those earth layers that the well crossed. It was assumed that a granite sequence extends to a depth of 5 km, after which stronger and more ancient basalt rocks were expected.
So, the north-west of the Kola Peninsula, 10 km from the city of Zapolyarny, not far from our border with Norway, was chosen as the drilling site. Zapolyarny is a small town that grew up in the fifties next to a nickel plant. Among the hilly tundra on a hillock blown by all the winds and snowstorms, there is a "square", each side of which is formed from seven five-story houses. Inside there are two streets, at their intersection there is a square where the House of Culture and the hotel stand. A kilometer from the town, behind the ravine, the buildings and tall chimneys of the nickel plant are visible, behind it, along the mountain slope, waste rock dumps from the nearest quarry darken. Near the town there is a highway to the city of Nikel and to a small lake, on the other side of which is already Norway.
The land of those places in abundance keeps traces of the past war. When you travel by bus from Murmansk to Zapolyarny, about half way you cross the small river Zapadnaya Litsa, on its bank there is a memorial obelisk. This is the only place in all of Russia where the front stood motionless during the war from 1941 to 1944, resting against the Barents Sea. Although there were fierce battles all the time and the losses on both sides were huge. The Germans tried unsuccessfully to break through to Murmansk, the only ice-free port in our North. In the winter of 1944, Soviet troops managed to break through the front.
On this hook, a string of pipes was lowered and raised. On the left - in a basket - there are 33-meter pipes prepared for descent - "candles".
Kola superdeep well. In the figure on the right: A. Forecast of the geological section. B. Geological section constructed on the basis of SG drilling data (arrows from column A to column B indicate at what depth the predicted rocks are encountered). In this section, the upper part (up to 7 km) is a Proterozoic sequence with layers of volcanic (diabase) and sedimentary rocks (sandstones, dolomites). Below 7 km there is an Archean stratum with repeating rock units (mainly gneisses and amphibolites). Its age is 2.86 billion years. C. The borehole with many drilled and lost boreholes (below 7 km) is shaped like the branched roots of a giant plant. The well seems to meander, because the drill is constantly deviated towards less durable rocks.
From Zapolyarny to Superdeep - 10 km. The road goes past the plant, then along the edge of the quarry and then climbs uphill. A small basin opens from the pass, in which a drilling rig is installed. Its height is from a twenty-story building. "Shift workers" came here from Zapolyarny to each shift. In total, about 3,000 people worked on the expedition, they lived in the city in two houses. The grumbling of some mechanisms was heard around the clock from the drilling rig. Silence meant that for some reason there was a break in drilling. In winter, during the long polar night - and it lasts there from November 23 to January 23 - the entire drilling rig was lit up with lights. Often, the light of the aurora was added to them.
A little about the staff. A good, highly qualified team of workers gathered in the Kola geological exploration expedition, created for drilling. D. Huberman was almost always the head of the GRE, a talented leader who selected the team. Chief engineer I. Vasilchenko was responsible for drilling. The rig was commanded by A. Batishchev, whom everyone called simply Lekha. V. Laney was in charge of geology, and Yu. Kuznetsov was in charge of geophysics. Huge work on core processing and creation of the core storage was carried out by geologist Yu. Smirnov - the one who had the "cherished locker", which we will tell about later. More than 10 research institutes took part in the research on the SG. The team also had its own "kulibins" and "left-handers" (S. Tserikovsky was especially distinguished), who invented and manufactured various devices, sometimes allowing them to get out of the most difficult, seemingly hopeless situations. They themselves created many of the necessary mechanisms here in well-equipped workshops.
DRILLING HISTORY
Drilling of the well began in 1970. Sinking to a depth of 7263 m took 4 years. It was driven by a serial installation, which is usually used in the extraction of oil and gas. Because of the constant winds and cold, the entire tower had to be sheathed to the top with wooden shields. Otherwise, it is simply impossible for someone who must stand at the top during the lifting of the pipe string to work.
Then there was a one-year break associated with the construction of a new derrick and the installation of a specially designed drilling rig - "Uralmash-15000". It was with her help that all further ultra-deep drilling was carried out. The new installation has more powerful automated equipment. Turbine drilling was used - this is when not the entire string rotates, but only the drill head. Drilling fluid was fed through the column under pressure, which rotated the multi-stage turbine below. Its total length is 46 m. The turbine ends with a drilling head with a diameter of 214 mm (it is often called a crown), which has an annular shape, so an undrilled column of rock remains in the middle - a core with a diameter of 60 mm. A pipe passes through all sections of the turbine - a core receiver, where columns of mined rock are collected. The crushed rock, together with the drilling fluid, is carried along the well to the surface.
On the core samples on the right, oblique stripes are clearly visible, which means that here the well passed through the layers located obliquely.
The mass of the string immersed in the well with drilling fluid is about 200 tons. This despite the fact that specially designed pipes made of light alloys were used. If the column is made of ordinary steel pipes, it will break from its own weight.
There are many difficulties, sometimes completely unexpected, in the process of drilling at great depths and with the selection of cores.
Penetration in one trip, determined by the wear of the drill head, is usually 7-10 m. (A trip, or a cycle, is the descent of a string with a turbine and a drilling tool, the actual drilling and a complete rise of the string.) The drilling itself takes 4 hours. And the descent and ascent of the 12-kilometer column takes 18 hours. When lifting, the string is automatically disassembled into sections (candles) 33 m long. On average, 60 m were drilled per month. 50 km of pipes were used to drill the last 5 km of the well. That's how worn they are.
Up to a depth of about 7 km, the well crossed strong, relatively homogeneous rocks, and therefore the wellbore was flat, almost corresponding to the diameter of the drill head. Work progressed, one might say, calmly. However, at a depth of 7 km, less strong fractured, interbedded with small very hard interlayers of rocks - gneisses, amphibolites - went. Drilling has become more difficult. The trunk took an oval shape, many cavities appeared. Accidents have become more frequent.
The figure shows the initial forecast of the geological section and the one made on the basis of drilling data. It is interesting to note (column B) that the formation inclination along the well is about 50 degrees. Thus, it is clear that the rocks intersected by the well come to the surface. It is here that one can recall the already mentioned "cherished locker" of the geologist Y. Smirnov. There, on one side, he had samples obtained from the well, and on the other, taken on the surface at that distance from the drilling rig, where the corresponding layer goes up. The coincidence of breeds is almost complete.
The year 1983 was marked by a hitherto unsurpassed record: the drilling depth exceeded 12 km. Work has been suspended.
The International Geological Congress was approaching, which, according to the plan, was held in Moscow. The Geoexpo exhibition was being prepared for it. It was decided not only to read the reports on the results achieved at the SG, but also to show the congress participants the work in kind and the extracted rock samples. The monograph "Kola Superdeep" was published for the congress.
At the Geoexpo exhibition, there was a large stand dedicated to the work of the SG and the most important thing - achieving a record depth. There were impressive graphs telling about the technique and technology of drilling, mined rock samples, photographs of equipment and the team at work. But the greatest attention of the participants and guests of the congress was attracted by one non-traditional detail for an exhibition show: the most common and already slightly rusted drill head with worn carbide teeth. The label said that it was she who was used when drilling at a depth of more than 12 km. This drill head amazed even specialists. Probably, everyone involuntarily expected to see some kind of miracle of technology, maybe with diamond equipment ... And they still did not know that a large pile of exactly the same already rusted drill heads was assembled on the SG next to the drilling rig: after all, they had to be replaced with new ones for about every 7-8 meters drilled.
Many congress delegates wanted to see with their own eyes the unique drilling rig on the Kola Peninsula and make sure that a record drilling depth had indeed been achieved in the Union. Such a departure took place. There, a meeting of the congress section was held on the spot. The delegates were shown the drilling rig, while they were lifting a string from the well, disconnecting 33-meter sections from it. Photos and articles about the SG were published in newspapers and magazines in almost all countries of the world. A postage stamp was issued, special cancellation of envelopes was organized. I will not list the names of the winners of various awards and those awarded for their work ...
But the holidays were over, we had to continue drilling. And it began with the largest accident on the very first flight on September 27, 1984 - a "black date" in the history of the SG. The well does not forgive when it is left unattended for a long time. During the time until drilling was carried out, changes inevitably occurred in its walls, those that were not fixed with a cemented steel pipe.
At first everything went smoothly. The drillers carried out their usual operations: one by one they lowered the sections of the drill string, to the last, upper one, they connected the drilling fluid supply pipe, turned on the pumps. We started drilling. The instruments on the console in front of the operator showed the normal mode of operation (the number of revolutions of the drill head, its pressure on the rock, the fluid flow rate for the rotation of the turbine, etc.).
Having drilled another 9-meter segment at a depth of more than 12 km, which took 4 hours, they reached a depth of 12.066 km. Prepare for the rise of the column. We tried. Doesn't go. At such depths, "sticking" has been observed more than once. This is when some section of the column seems to stick to the walls (maybe something crumbled from above, and it jammed a little). To move the column from its place, a force exceeding its weight (about 200 tons) is required. So did this time, but the column did not move. We added a little effort, and the arrow of the device sharply slowed down the readings. The column became much lighter, there could not have been such a weight loss during the normal course of the operation. We began to rise: one by one, the sections were unscrewed one after the other. During the last ascent, a shortened piece of pipe with an uneven bottom edge hung on a hook. This meant that not only the turbodrill, but also 5 km of drill pipes remained in the well...
Seven months trying to get them. After all, we lost not just 5 km of pipes, but the results of five years of work.
Then all attempts to return the lost were stopped and they began to drill again from a depth of 7 km. I must say that it is after the seventh kilometer that the geological conditions here are especially difficult for work. The drilling technology of each step is worked out by trial and error. And starting from a depth of about 10 km - even more difficult. Drilling, operation of equipment and equipment are at the limit.
Therefore, accidents here have to be expected at any moment. They are preparing for them. Methods and means of their elimination are thought over in advance. A typical complex accident is a breakage of the drilling assembly along with part of the drill string. The main method of eliminating it is to create a ledge just above the lost part and from this place to drill a new bypass hole. A total of 12 such bypass holes were drilled in the well. Four of them are from 2200 to 5000 m long. The main cost of such accidents is years of lost labor.
Only in the everyday view, a well is a vertical "hole" from the surface of the earth to the bottom. In reality, this is far from the case. Especially if the well is ultra-deep and crosses inclined seams of various densities. Then it seems to meander, because the drill constantly deviates towards less durable rocks. After each measurement, showing that the inclination of the well exceeds the allowable one, it must be tried to "return to its place". To do this, together with the drilling tool, special "deflectors" are lowered, which help to reduce the angle of inclination of the well during drilling. Accidents often occur with the loss of drilling tools and parts of pipes. After that, a new trunk has to be done, as we have already said, stepping aside. So imagine what a well looks like in the ground: something like the roots of a giant plant branched at a depth.
This is the reason for the special duration of the last phase of drilling.
After the largest accident - the "black date" of 1984 - they again approached a depth of 12 km only after 6 years. In 1990, a maximum was reached - 12,262 km. After a few more accidents, we were convinced that we couldn’t get deeper. All the possibilities of modern technology have been exhausted. It seemed as if the Earth no longer wanted to reveal its secrets. Drilling was stopped in 1992.
RESEARCH. OBJECTIVES AND METHODS
One of the very important goals of drilling was to obtain a core column of rock samples along the entire length of the borehole. And this task has been completed. The longest core in the world was marked out like a ruler in meters and placed in the appropriate order in boxes. The box number and sample numbers are indicated at the top. There are almost 900 such boxes in stock.
Now it remains only to study the core, which is really indispensable in determining the structure of the rock, its composition, properties, and age.
But a rock sample raised to the surface has different properties than in the massif. Here, at the top, he is freed from the enormous mechanical stresses that exist at depth. During drilling, it cracked and became saturated with drilling mud. Even if deep conditions are recreated in a special chamber, the parameters measured on the sample still differ from those in the array. And one more small "hack": for every 100 m of a drilled well, 100 m of core are not obtained. On the SG from depths of more than 5 km, the average core recovery was only about 30%, and from depths of more than 9 km, these were sometimes only individual plaques 2-3 cm thick, corresponding to the most durable interlayers.
So, the core taken from the well on the SG does not provide complete information about deep rocks.
The wells were drilled for scientific purposes, so the whole range of modern research methods was used. In addition to extracting the core, studies of the properties of rocks in their natural occurrence were necessarily carried out. The technical condition of the well was constantly monitored. The temperature was measured throughout the wellbore, natural radioactivity - gamma radiation, induced radioactivity after pulsed neutron irradiation, electrical and magnetic properties of rocks, elastic wave propagation velocity, and the composition of gases in the well fluid.
To a depth of 7 km, serial instruments were used. Work at greater depths and at higher temperatures required the creation of special heat and pressure resistant instruments. Particular difficulties arose during the last stage of drilling; when the temperature in the well approached 200°C and the pressure exceeded 1000 atmospheres, the serial instruments could no longer work. The geophysical design bureaus and specialized laboratories of several research institutes came to the rescue, producing single copies of heat and pressure resistant instruments. Thus, all the time they worked only on domestic equipment.
In a word, the well was investigated in sufficient detail to its entire depth. The studies were carried out in stages, approximately once a year, after deepening the well by 1 km. Each time after that, the reliability of the received materials was assessed. Appropriate calculations made it possible to determine the parameters of a particular breed. We discovered a certain alternation of layers and already knew what rocks the caverns are confined to and the partial loss of information associated with them. We learned to identify rocks literally by "crumbs" and on this basis to recreate a complete picture of what the well "hidden". In short, we managed to build a detailed lithological column - to show the alternation of rocks and their properties.
FROM OWN EXPERIENCE
Approximately once a year, when the next stage of drilling was completed - deepening the well by 1 km, I also went to the SG to take the measurements that I was entrusted with. The well at this time was usually washed out and provided for research for a month. The time of the planned stop was always known in advance. The telegram-call for work also came in advance. The equipment has been checked and packaged. The formalities related to closed work in the border zone have been completed. Finally everything is settled. Let's go.
Our group is a small friendly team: a downhole tool developer, a developer of new ground equipment, and I am a methodologist. We arrive 10 days before measurements. We get acquainted with the data on the technical condition of the well. We draw up and approve a detailed measurement program. We assemble and calibrate equipment. We are waiting for a call - a call from the well. Our turn to "dive" is the third, but if there is a refusal from the predecessors, the well will be provided to us. This time they are all right, they say that tomorrow morning they will finish. With us in the same team of geophysicists - operators who register the signals received from the equipment in the well and command all operations for lowering and raising the downhole tool, as well as mechanics on the lift, they control the winding from the drum and winding on it those same 12 km of cable on which the tool is lowered into the well. Drillers are also on duty.
Work has begun. The device is lowered into the well for several meters. Last check. Go. The descent is slow - about 1 km / h, with continuous monitoring of the signal coming from below. So far so good. But at the eighth kilometer, the signal twitched and disappeared. So something is wrong. Full lift. (Just in case, we have prepared a second set of equipment.) We begin checking all the details. This time the cable was faulty. He is being replaced. This takes more than a day. The new descent took 10 hours. Finally, the observer of the signal said: "Arrived at the eleventh kilometer." Command to operators: "Start recording". What and how is pre-scheduled according to the program. Now you need to lower and raise the downhole tool several times in a given interval in order to take measurements. This time the equipment worked fine. Now full lift. We climbed up to 3 km, and suddenly the call of the winch (he is our man with humor): "The rope is over." How?! What?! Alas, the cable broke... The downhole tool and 8 km of cable were left lying at the bottom... Fortunately, a day later, the drillers managed to pick it all up, using the methodology and devices developed by local craftsmen to eliminate such emergencies.
RESULTS
The tasks set in the ultra-deep drilling project have been fulfilled. Special equipment and technology for ultra-deep drilling, as well as for the study of wells drilled to a great depth, have been developed and created. We received information, one might say, "first-hand" about the physical state, properties and composition of rocks in their natural occurrence and from the core to a depth of 12,262 m.
The well gave out an excellent gift to the motherland at a shallow depth - in the range of 1.6-1.8 km. Industrial copper-nickel ores were discovered there - a new ore horizon was discovered. And very handy, because the local nickel plant is already running out of ore.
As noted above, the geological forecast of the well section did not come true (see the figure on page 39.). The picture that was expected during the first 5 km in the well stretched for 7 km, and then completely unexpected rocks appeared. The basalts predicted at a depth of 7 km were not found, even when they dropped to 12 km.
It was expected that the boundary that gives the most reflection in seismic sounding is the level where the granites pass into a more durable basalt layer. In reality, it turned out that less durable and less dense fractured rocks - Archean gneisses - are located there. This was not expected at all. And this is a fundamentally new geological and geophysical information that allows you to interpret the data of deep geophysical surveys in a different way.
The data on the process of ore formation in the deep layers of the earth's crust also turned out to be unexpected and fundamentally new. So, at depths of 9-12 km, highly porous fractured rocks saturated with underground highly mineralized waters were encountered. These waters are one of the sources of ore formation. Previously, it was believed that this was possible only at much shallower depths. It was in this interval that an increased gold content was found in the core - up to 1 g per 1 ton of rock (a concentration that is considered suitable for industrial development). But will it ever be profitable to mine gold from such a depth?
The ideas about the thermal regime of the earth's interior, about the deep distribution of temperatures in the areas of basalt shields, have also changed. At a depth of more than 6 km, a temperature gradient of 20°C per 1 km was obtained instead of the expected (as in the upper part) 16°C per 1 km. It was revealed that half of the heat flux is of radiogenic origin.
Having drilled the unique Kola super-deep well, we learned a lot and at the same time realized how little we still know about the structure of our planet.
Candidate of Technical Sciences A. OSADCHI.
LITERATURE
Kola superdeep. Moscow: Nedra, 1984.
Kola superdeep. Scientific results and research experiences. M., 1998.
Kozlovsky E. A. World Forum of Geologists. "Science and Life" No. 10, 1984.
Kozlovsky E. A. Kola superdeep. "Science and Life" No. 11, 1985.
Sredao.ru cottage settlements from HABITAT
Sredao.ru townhouses from real estate agency HABITAT
The 20th century was marked by the triumph of man in the air and the conquest of the deepest depressions in the oceans. Only the dream of penetrating to the heart of our planet and knowing the hitherto hidden life of its bowels still remains unattainable. "Journey to the Center of the Earth" promises to be extremely difficult and exciting, fraught with a lot of surprises and incredible discoveries. The first steps on this path have already been taken - several dozen ultra-deep wells have been drilled in the world. The information obtained with the help of ultra-deep drilling turned out to be so stunning that it shook the well-established ideas of geologists about the structure of our planet and provided the richest materials for researchers in various fields of knowledge.
touch the mantle
Hardworking Chinese in the 13th century dug wells 1,200 meters deep. Europeans broke the Chinese record in 1930, having learned to pierce the earth's firmament with the help of drilling rigs for 3 kilometers. In the late 1950s, the wells were extended to 7 kilometers. The era of ultra-deep drilling began.
Like most global projects, the idea to drill into the Earth's upper shell arose in the 1960s, at the height of space flight and belief in the limitless possibilities of science and technology. The Americans conceived nothing less than to penetrate the entire earth's crust with a borehole and obtain samples of the rocks of the upper mantle. Ideas about the mantle then (as, indeed, now) were based only on indirect data - the speed of propagation of seismic waves in the depths, the change in which was interpreted as the boundary of rock layers of different ages and compositions. Scientists believed that the earth's crust is like a sandwich: young rocks on top, ancient ones on the bottom. However, only ultra-deep drilling could give a true picture of the structure and composition of the outer shell of the Earth and the upper mantle.
Mohol project
In 1958, the Mohol ultra-deep drilling program appeared in the United States. This is one of the most daring and mysterious projects of post-war America. Like many other programs, Mohol was designed to overtake the USSR in scientific rivalry by setting a world record in ultra-deep drilling. The name of the project comes from the words "Mohorovicic" - the name of a Croatian scientist who identified the interface between the earth's crust and mantle - the Moho border, and "hole", which in English means "well". The creators of the program decided to drill in the ocean, where, according to geophysicists, the earth's crust is much thinner than on the continents. It was necessary to lower the pipes several kilometers into the water, go 5 kilometers of the ocean floor and reach the upper mantle.
In April 1961, off the island of Guadeloupe in the Caribbean Sea, where the water column reaches 3.5 km, geologists drilled five wells, the deepest of which entered the bottom at 183 meters. According to preliminary calculations, in this place, under sedimentary rocks, they expected to meet the upper layer of the earth's crust - granite. But the core lifted from under the sediments contained pure basalts - a kind of antipode of granites. The result of drilling discouraged and at the same time inspired scientists, they began to prepare a new phase of drilling. But when the cost of the project exceeded $100 million, the US Congress stopped funding. "Mohol" did not answer any of the questions posed, but it showed the main thing - ultra-deep drilling in the ocean is possible.
Funeral postponed
Ultra-deep drilling made it possible to look into the bowels and understand how rocks behave at high pressures and temperatures. The idea that rocks become denser with depth and their porosity decreases turned out to be wrong, as well as the point of view about dry bowels. This was first discovered when drilling the Kola Superdeep, other wells in ancient crystalline strata confirmed the fact that at a depth of many kilometers the rocks are broken by cracks and penetrated by numerous pores, and aqueous solutions move freely under a pressure of several hundred atmospheres. This discovery is one of the most important achievements of ultra-deep drilling. It made us turn again to the problem of radioactive waste disposal, which was supposed to be placed in deep wells, which seemed completely safe. Given the information on the state of the subsoil, obtained during ultra-deep drilling, projects for the creation of such burial sites now look very risky.
In search of the cooled hell
Since then, the world has become ill with ultra-deep drilling. In the United States, a new program for studying the ocean floor (Deep Sea Drilling Project) was being prepared. Built specifically for this project, the Glomar Challenger vessel spent several years in the waters of various oceans and seas, drilling almost 800 wells in their bottom, reaching a maximum depth of 760 m. By the mid-1980s, the results of offshore drilling confirmed the theory of plate tectonics. Geology as a science was born again. Meanwhile, Russia went its own way. Interest in the problem, awakened by the success of the United States, resulted in the program "Study of the bowels of the Earth and ultra-deep drilling", but not in the ocean, but on the continent. Despite centuries of history, continental drilling seemed to be a completely new thing. After all, it was about previously unattainable depths - more than 7 kilometers. In 1962, Nikita Khrushchev approved this program, although he was guided by political motives rather than scientific ones. He did not want to lag behind the United States.
The well-known oilman, Doctor of Technical Sciences Nikolay Timofeev, headed the newly created laboratory at the Institute of Drilling Technology. He was instructed to substantiate the possibility of ultra-deep drilling in crystalline rocks - granites and gneisses. The research took 4 years, and in 1966 the experts issued a verdict - it is possible to drill, and not necessarily with the technology of tomorrow, the equipment that is already there is enough. The main problem is the heat at depth. According to calculations, as it penetrates into the rocks that make up the earth's crust, the temperature should increase by 1 degree every 33 meters. This means that at a depth of 10 km we should expect about 300°C, and at 15 km - almost 500°C. Drilling tools and devices will not withstand such heating. It was necessary to look for a place where the bowels are not so hot ...
Such a place was found - an ancient crystalline shield of the Kola Peninsula. The report, prepared at the Institute of Physics of the Earth, said: over the billions of years of its existence, the Kola shield has cooled down, the temperature at a depth of 15 km does not exceed 150 ° C. And geophysicists have prepared an approximate section of the bowels of the Kola Peninsula. According to them, the first 7 kilometers are granite strata of the upper part of the earth's crust, then the basalt layer begins. Then the idea of a two-layer structure of the earth's crust was generally accepted. But as it turned out later, both physicists and geophysicists were wrong. The drilling site was chosen on the northern tip of the Kola Peninsula near Lake Vilgiskoddeoaivinjärvi. In Finnish, it means "Under the wolf mountain", although there is no mountain or wolves in that place. Drilling of the well, the design depth of which was 15 kilometers, began in May 1970.
The disappointment of the Swedes
In the late 1980s, in Sweden, in search of non-biological natural gas, a well was drilled to a depth of 6.8 km. Geologists decided to test the hypothesis that oil and gas are formed not from dead plants, as most scientists believe, but through mantle fluids - hot mixtures of gases and liquids. Fluids saturated with hydrocarbons seep from the mantle into the earth's crust and accumulate in large quantities. In those years, the idea of the origin of hydrocarbons not from the organic matter of sedimentary strata, but through deep fluids was a novelty, many wanted to test it. It follows from this idea that hydrocarbon reserves may contain not only sedimentary, but also volcanic and metamorphic rocks. That is why Sweden, mostly located on an ancient crystalline shield, undertook to make an experiment.
Silyan Ring crater with a diameter of 52 km was chosen for drilling. According to geophysical data, at a depth of 500-600 meters there were calcined granites - a possible seal for the underlying hydrocarbon reservoir. Measurements of the acceleration of gravity, the change in which can be used to judge the composition and density of rocks occurring in the bowels of the rocks, indicated the presence of highly porous rocks at a depth of 5 km - a possible reservoir of oil and gas. The drilling results disappointed scientists and investors who invested $60 million in these works. The passed strata did not contain commercial reserves of hydrocarbons, only manifestations of oil and gas of clearly biological origin from ancient bitumen. In any case, no one has been able to prove the opposite.
Tool for the underworld
The drilling of the Kola well SG-3 did not require the creation of fundamentally new devices and giant machines. We started working with what we already had: the Uralmash 4E unit with a lifting capacity of 200 tons and light-alloy pipes. What was really needed at that time was non-standard technological solutions. Indeed, in solid crystalline rocks no one has drilled to such a great depth, and what will be there, they imagined only in general terms. Experienced drillers, however, understood that no matter how detailed the project was, the real well would be much more complicated. After 5 years, when the depth of the SG-3 well exceeded 7 kilometers, a new drilling rig "Uralmash 15,000" was installed - one of the most modern at that time. Powerful, reliable, with an automatic tripping mechanism, it could withstand a pipe string up to 15 km long. The drilling rig has turned into a fully sheathed tower 68 m high, recalcitrant to the strong winds raging in the Arctic. A mini-factory, scientific laboratories and a core storage facility have grown up nearby.
When drilling to shallow depths, a motor that rotates a string of pipes with a drill at the end is installed on the surface. The drill is an iron cylinder with teeth made of diamonds or hard alloys - a crown. This crown bites into the rocks and cuts out of them a thin column - core. To cool the tool and remove small debris from the well, drilling fluid is injected into it - liquid clay, which circulates all the time through the wellbore, like blood in vessels. After some time, the pipes are raised to the surface, freed from the core, the crown is changed and the column is lowered into the bottomhole again. This is how normal drilling works.
And if the barrel length is 10-12 kilometers with a diameter of 215 millimeters? The string of pipes becomes the thinnest thread lowered into the well. How to manage it? How to see what is happening in the face? Therefore, at the Kola well, miniature turbines were installed at the bottom of the drill string, they were launched by drilling fluid injected through pipes under pressure. The turbines rotated the carbide bit and cut out the core. The whole technology was well developed, the operator on the control panel saw the rotation of the crown, knew its speed and could control the process.
Every 8-10 meters, a multi-kilometer column of pipes had to be lifted up. The descent and ascent took a total of 18 hours.
Diamond dreams of the Volga region
When small diamonds were found in the Nizhny Novgorod region, this puzzled geologists a lot. Of course, it was easiest to assume that the gems were brought by a glacier or river waters from somewhere in the north. But what if the local subsoil hides a kimberlite pipe - a reservoir of diamonds? It was decided to test this hypothesis in the late 1980s, when the scientific drilling program in Russia was gaining momentum. The location for drilling was chosen to the north of Nizhny Novgorod, in the center of a giant ring structure, which stands out well in the relief. Some considered it to be a meteorite crater, others - an explosion pipe or a volcano vent. Drilling was stopped when the Vorotilovskaya well reached a depth of 5,374 m, of which more than a kilometer was in the crystalline basement. Kimberlites were not found there, but in fairness it should be said that the dispute about the origin of this structure was also not put an end to. The facts extracted from the depths were equally suitable for the supporters of both hypotheses, in the end, each remained unconvinced. And the well was turned into a deep geolaboratory, which still operates today.
The insidiousness of the number "7"
7 kilometers - the mark for the Kola superdeep fatal. Behind it began the unknown, many accidents and a continuous struggle with rocks. The barrel could not be kept upright. When 12 km were covered for the first time, the well deviated from the vertical by 21°. Although the drillers had already learned to work with the incredible curvature of the trunk, it was impossible to go any further. The well had to be re-drilled from the mark of 7 kilometers. To get a vertical hole in hard formations, you need a very rigid bottom of the drill string so that it enters the subsoil like butter. But another problem arises - the well is gradually expanding, the drill dangles in it, as in a glass, the walls of the barrel begin to collapse and can crush the tool. The solution to this problem turned out to be original - the pendulum technology was applied. The drill was artificially swung in the well and suppressed strong vibrations. Due to this, the trunk turned out vertical.
The most common accident on any drilling rig is a pipe string break. Usually the pipes try to seize again, but if this happens at a great depth, then the problem becomes unrecoverable. It is useless to look for a tool in a 10-kilometer well, they threw such a hole and started a new one, a little higher. Breakage and loss of pipes on SG-3 happened many times. As a result, in its lower part, the well looks like the root system of a giant plant. The branching of the well upset the drillers, but turned out to be happiness for geologists, who unexpectedly received a three-dimensional picture of an impressive segment of ancient Archean rocks that formed more than 2.5 billion years ago.
In June 1990, SG-3 reached a depth of 12,262 m. They began to prepare the well for drilling up to 14 km, and then an accident occurred again - at the level of 8,550 m, the pipe string broke. The continuation of the work required a long preparation, updating equipment and new costs. In 1994, drilling of the Kola Superdeep was stopped. After 3 years, she got into the Guinness Book of Records and still remains unsurpassed. Now the well is a laboratory for studying deep bowels.
Secret subsoil
SG-3 was a secret facility from the very beginning. Both the border zone, and strategic deposits in the district, and scientific priority are to blame. The first foreigner to visit the rig was one of the leaders of the Academy of Sciences of Czechoslovakia. Later, in 1975, an article about the Kola Superdeep was published in Pravda signed by the Minister of Geology Alexander Sidorenko. There were still no scientific publications on the Kola well, but some information leaked abroad. The world began to learn more from rumors - the deepest well is being drilled in the USSR.
The veil of secrecy, probably, would have hung over the well until the very “perestroika” had it not been for the World Geological Congress in Moscow in 1984. Carefully prepared for such a major event in the scientific world, a new building was even built for the Ministry of Geology - many participants were expecting it. But foreign colleagues were primarily interested in the Kola Superdeep! The Americans did not believe that we had it at all. The depth of the well by that time had reached 12,066 meters. There was no point in hiding the object anymore. In Moscow, the congress participants were treated to an exhibition of achievements in Russian geology, one of the stands was dedicated to the SG-3 well. Experts from all over the world looked in bewilderment at an ordinary drill head with worn carbide teeth. And this is how they drill the deepest well in the world? Incredible! A large delegation of geologists and journalists went to the village of Zapolyarny. Visitors were shown the drilling rig in action, and 33-meter pipe sections were taken out and disconnected. There were heaps of exactly the same drilling heads around, like the one that lay on the stand in Moscow.
From the Academy of Sciences, the delegation was received by a well-known geologist, Academician Vladimir Belousov. During a press conference from the audience, he was asked a question:
- What is the most important thing shown by the Kola well?
- Lord! The main thing is that it showed that we know nothing about the continental crust, - the scientist answered honestly.
Deep Surprise
Of course, they knew something about the earth's crust of the continents. The fact that the continents are composed of very ancient rocks, aged from 1.5 to 3 billion years, was not refuted even by the Kola well. However, the geological section compiled on the basis of the SG-3 core turned out to be exactly the opposite of what scientists imagined earlier. The first 7 kilometers were composed of volcanic and sedimentary rocks: tuffs, basalts, breccias, sandstones, dolomites. Deeper lay the so-called Conrad section, after which the velocity of seismic waves in the rocks increased sharply, which was interpreted as the boundary between granites and basalts. This section was passed long ago, but the basalts of the lower layer of the earth's crust did not appear anywhere. On the contrary, granites and gneisses began.
The section of the Kola well refuted the two-layer model of the earth's crust and showed that the seismic sections in the bowels are not the boundaries of layers of rocks of different composition. Rather, they indicate a change in the properties of the stone with depth. At high pressure and temperature, the properties of rocks, apparently, can change dramatically, so that granites in their physical characteristics become similar to basalts, and vice versa. But the “basalt” raised to the surface from a depth of 12 km immediately became granite, although it experienced a severe attack of “caisson disease” along the way - the core crumbled and disintegrated into flat plaques. The further the well went, the fewer quality samples fell into the hands of scientists.
The depth contained many surprises. It used to be natural to think that with distance from the earth's surface, with increasing pressure, rocks become more monolithic, with a small number of cracks and pores. SG-3 convinced scientists otherwise. Starting from 9 kilometers, the strata turned out to be very porous and literally crammed with cracks through which aqueous solutions circulated. Later, this fact was confirmed by other ultra-deep wells on the continents. At depth it turned out to be much hotter than expected: by as much as 80 °! At the mark of 7 km the temperature in the face was 120°C, at 12 km it reached 230°C. In the samples of the Kola well, scientists discovered gold mineralization. Inclusions of the precious metal were found in ancient rocks at a depth of 9.5-10.5 km. However, the concentration of gold was too low to declare a deposit - an average of 37.7 mg per ton of rock, but sufficient to expect it in other similar places.
Warmth of the home planet
The high temperatures met by underground drillers led scientists to the idea of using this almost inexhaustible source of energy. For example, in young mountains (which are the Caucasus, the Alps, the Pamirs), at a depth of 4 km, the temperature of the bowels will reach 200°C. This natural battery can be made to work for you. It is necessary to drill two deep wells side by side and connect them with horizontal drifts. Then water is pumped into one well, and hot steam is extracted from the other, which will be used to heat the city or receive another type of energy. A serious problem for such enterprises can be caustic gases and fluids, which are not uncommon in seismically active areas. In 1988, the Americans had to complete the drilling of a well on the shelf of the Gulf of Mexico off the coast of Alabama, reaching a depth of 7,399 m. The reason for this was the subsurface temperature, which reached 232 ° C, very high pressure and acid gas emissions. In those areas where there are deposits of hot groundwater, they can be extracted directly from wells from fairly deep horizons. Such projects are suitable for the regions of the Caucasus, the Pamirs, the Far East. However, the high cost of the work limits the depth of production to four kilometers.
Following the Russian trail
The demonstration of the Kola well in 1984 made a deep impression on the world community. Many countries have begun to prepare projects for scientific drilling on the continents. Such a program was approved in Germany in the late 1980s. The ultra-deep well KTB Hauptborung was drilled from 1990 to 1994, according to the plan, it was supposed to reach a depth of 12 km, but due to unpredictably high temperatures, it was only possible to reach the mark of 9.1 km. Thanks to the openness of data on drilling and scientific work, good technology and documentation, the KTV ultra-deep well remains one of the most famous in the world.
The location for drilling this well was chosen in the southeast of Bavaria, on the remains of an ancient mountain range, whose age is estimated at 300 million years. Geologists believed that somewhere here there is a zone of connection of two plates, which were once the shores of the ocean. According to scientists, over time, the upper part of the mountains was erased, exposing the remains of the ancient oceanic crust. Even deeper, ten kilometers from the surface, geophysicists discovered a large body with an abnormally high electrical conductivity. Its nature was also hoped to be clarified with the help of a well. But the main task was to reach a depth of 10 km in order to gain experience in ultra-deep drilling. Having studied the materials of the Kola SG-3, the German drillers decided to first go through a test well 4 km deep in order to get a more accurate idea of the working conditions in the bowels, test the equipment and take a core. At the end of the pilot work, much of the drilling and scientific equipment had to be redone, something to be created anew.
The main - ultra-deep - well KTV Hauptborung was laid just two hundred meters from the first one. For the work, they built an 83-meter tower and created the most powerful drilling rig at that time with a lifting capacity of 800 tons. Many drilling operations have been automated, primarily the mechanism for lowering and retrieving a pipe string. A self-guided vertical drilling system made it possible to make an almost sheer shaft. Theoretically, with such equipment it was possible to drill to a depth of 12 kilometers. But the reality, as always, turned out to be more complicated, and the plans of scientists did not come true.
Problems at the KTV well began after a depth of 7 km, repeating much of the fate of the Kola Superdeep. At first, it is believed that due to the high temperature, the vertical drilling system broke down and the shaft went sideways. At the end of the work, the bottomhole deviated from the vertical by 300 m. Then, more complicated accidents began - a break in the drill string. As well as on Kolskaya, new shafts had to be drilled. The narrowing of the well caused certain difficulties - at the top its diameter was 71 cm, at the bottom - 16.5 cm.
It cannot be said that the scientific results of the KTV Hauptborung captured the imagination of scientists. At depth, amphibolites and gneisses, ancient metamorphic rocks, were mainly deposited. The zone of convergence of the ocean and the remains of the oceanic crust were not found anywhere. Perhaps they are in another place, there is also a small crystalline massif, uplifted to a height of 10 km. A graphite deposit was discovered a kilometer from the surface.
In 1996, the KTV well, which cost the German budget $338 million, came under the patronage of the Research Center for Geology in Potsdam, and it was turned into a laboratory for deep subsurface observations and a tourist attraction.
Why isn't the moon made of cast iron?
“Because there would not be enough iron for the Moon” - probably, this is how the opponents of the hypothesis, according to which the Moon broke away from the Earth, could answer its supporters. This hypothesis, however, did not arise from scratch, and scientists are considering several regions of the Earth, from where a piece of the planet the size of the moon could be knocked out. The Kola well offered its own version. In the 1970s, Soviet stations delivered several hundred grams of lunar soil to Earth. The substance was divided among the leading scientific centers of the country in order to conduct independent analyzes. A tiny sample also went to the Kola Science Center. Scientists from all over the region came to take a look at the curiosity, including employees of the well, which later became the deepest in the world. Is it a joke? Touch unearthly dust, look at it through a microscope. Later, experts investigated the lunar soil and published a monograph on this subject. By that time, the well in Zapolyarny had reached a decent depth, and the rocks lifted from the borehole were described in detail. And what? Samples of lunar soil, which the drillers once looked with awe, turned out to be one to one diabases from their well, from a depth of 3 km. Immediately, a hypothesis arose that the Moon broke away only from the Kola Peninsula about 1.5 billion years ago - such is the age of diabases. Although the question involuntarily arose - what was the size of this peninsula then? ..
To drill or not to drill?
The record of the Kola well is still unsurpassed, although it is certainly possible to go 14 or even 15 km deep into the Earth. However, it is unlikely that such a single effort will provide fundamentally new knowledge about the earth's crust, while ultra-deep drilling is a very expensive business. The times when it was used to test a variety of hypotheses are long gone. Wells deeper than 6-7 km for purely scientific purposes have almost ceased to be drilled. For example, only two objects of this kind remained in Russia - the Ural SG-4 and the En-Yakhinskaya well in Western Siberia. They are run by the state enterprise NPC Nedra, located in Yaroslavl. There are so many ultra-deep and deep wells drilled in the world that scientists do not have time to analyze the information. In recent years, geologists have been striving to study and generalize the facts obtained from great depths. Having learned to drill to great depths, people now want to better master the horizon available to them, to concentrate their efforts on practical tasks that will be useful right now. So in Russia, having completed the scientific drilling program, having drilled all 12 planned ultra-deep wells, they are now working on a system for the entire state, in which geophysical data obtained by “transmission” of the subsoil with seismic waves will be linked with information obtained by ultra-deep drilling. Without wells, sections of the earth's crust built by geophysicists are just models. In order for specific rocks to appear on these diagrams, drilling data is needed. Then geophysicists, whose work is much cheaper than drilling and cover a large area, will be able to predict mineral deposits much more accurately.
In the US, they continue to engage in a program of deep drilling of the ocean floor and conduct several interesting projects in zones of volcanic and tectonic activity of the earth's crust. So, in the Hawaiian Islands, researchers hoped to study the underground life of the volcano and get closer to the mantle tongue - the plume, which is believed to have given rise to these islands. The well at the foot of the Mauna Kea volcano was planned to be drilled to a depth of 4.5 km, but due to the enormous temperatures, only 3 km could be mastered. Another project is a deep observatory on the San Andreas Fault. Drilling of the well through this largest fault in the North American continent began in June 2004 and covered 2 out of 3 planned kilometers. In the deep laboratory, they intend to study the origin of earthquakes, which, perhaps, will make it possible to better understand the nature of these natural disasters and make their forecast.
While current ultra-deep drilling programs are no longer as ambitious as they used to be, they clearly have a bright future ahead of them. The day is not far off when the turn of great depths will come - there they will search for and discover new deposits of minerals. Already, oil and gas production in the United States from depths of 6-7 km is becoming commonplace. In the future, Russia will also have to pump hydrocarbons from such levels. As the Tyumen superdeep well showed, there are sedimentary rock strata promising for gas deposits 7 kilometers from the surface.
It is not for nothing that ultra-deep drilling is compared with the conquest of space. Such programs, on a global scale, absorbing all the best that humanity currently has, give impetus to the development of many industries, technology, and ultimately pave the way for a new breakthrough in science.
Devilish machinations
Once the Kola Superdeep was at the center of a global scandal. One fine morning in 1989, the director of the well, David Guberman, received a phone call from the editor-in-chief of the regional newspaper, the secretary of the regional committee, and a host of other people. Everyone wanted to know about the devil that the drillers allegedly raised from the bowels, as reported by some newspapers and radio stations around the world. The director was taken aback, and - it was from what! "Scientists have discovered hell", "Satan has escaped from hell" - read the headlines. As reported in the press, geologists working very far in Siberia, and maybe in Alaska or even the Kola Peninsula (journalists had no consensus on this), were drilling at a depth of 14.4 km, when suddenly the drill began to dangle strongly from side to side. This means that there is a big hole below, the scientists thought, apparently, the center of the planet is empty. Sensors lowered into the depths showed a temperature of 2,000 ° C, and super-sensitive microphones sounded ... the screams of millions of suffering souls. As a result, drilling was stopped due to fears of releasing infernal forces to the surface. Of course, Soviet scientists refuted this journalistic "duck", but the echoes of that old story wandered from newspaper to newspaper for a long time, turning into a kind of folklore. A few years later, when stories about hell had already been forgotten, employees of the Kola superdeep visited Australia with lectures. They were invited to a reception by the Governor of Victoria, a flirtatious lady, who greeted the Russian delegation with the question: “What the hell did you raise from there?”
The deepest wells in the world
1. Aralsor SG-1, Caspian lowland, 1962-1971, depth - 6.8 km. Search for oil and gas.
2. Biikzhalskaya SG-2, Caspian lowland, 1962-1971, depth - 6.2 km. Search for oil and gas.
3. Kola SG-3, 1970-1994, depth - 12,262 m. Design depth - 15 km.
4. Saatlinskaya, Azerbaijan, 1977-1990, depth - 8324 m. Design depth - 11 km.
5. Kolvinskaya, Arkhangelsk region, 1961, depth - 7,057 m.
6. Muruntau SG-10, Uzbekistan, 1984, depth -
3 km. Design depth - 7 km. Search for gold.
7. Timan-Pechora SG-5, North-East of Russia, 1984-1993, depth - 6904 m, design depth - 7 km.
8. Tyumenskaya SG-6, Western Siberia, 1987-1996, depth - 7,502 m. Design depth - 8 km. Search for oil and gas.
9. Novo-Elkhovskaya, Tatarstan, 1988, depth - 5,881 m.
10. Vorotilovskaya well, Volga region, 1989-1992, depth - 5374 m. Search for diamonds, study of the Puchezh-Katunkka astroblem.
11. Krivorozhskaya SG-8, Ukraine, 1984-1993, depth - 5382 m. Design depth - 12 km. Search for ferruginous quartzites.
Ural SG-4, Middle Urals. Founded in 1985. Design depth - 15,000 m. Current depth - 6,100 m. Search for copper ores, study of the structure of the Urals. En-Yakhtinskaya SG-7, Western Siberia. Design depth - 7,500 m. Current depth - 6,900 m. Oil and gas exploration.
Wells for oil and gas
early 70s
University, USA, depth - 8,686 m.
Baden Unit, USA, depth - 9,159 m.
Bertha Rogers, USA, depth - 9,583 m.
80s
Zisterdorf, Austria, depth 8,553 m.
Siljan Ring, Sweden, depth - 6.8 km.
Bighorn, USA, Wyoming, depth - 7,583 m.
KTV Hauptbohrung, Germany, 1990-1994, depth -
9,100 m. Design depth - 10 km. Scientific drilling.
At the edge of life
At the Limits of Life Extremophilic Bacteria Found in Rocks Excavated from a Depth of Several Kilometers DOSSIER One of the most amazing discoveries that scientists have made by drilling is the presence of life deep underground. And although this life is represented only by bacteria, its limits extend to incredible depths. Bacteria are ubiquitous. They mastered the underworld, it would seem, completely unsuitable for existence. Huge pressures, high temperatures, lack of oxygen and living space - nothing could become an obstacle to the spread of life. According to some estimates, the mass of microorganisms living underground can exceed the mass of all living creatures that inhabit the surface of our planet.
As early as the beginning of the 20th century, the American scientist Edson Bastin discovered bacteria in water from an oil-bearing horizon from a depth of several hundred meters. The microorganisms living there did not need oxygen and sunlight, they fed on organic compounds of oil. Bastin suggested that these bacteria have been living in isolation from the surface for 300 million years - since the oil field was formed. But his bold hypothesis remained unclaimed, they simply did not believe in it. Then it was believed that life is just a thin film on the surface of the planet.
Interest in deep life forms can be quite practical. In the 1980s, the US Department of Energy was looking for safe methods to dispose of radioactive waste. For these purposes, it was supposed to use mines in impenetrable rocks, where bacteria that feed on radionuclides live. In 1987, deep drilling of several wells began in South Carolina. From a depth of half a kilometer, scientists took samples, observing all kinds of precautions so as not to bring bacteria and air from the surface of the Earth. The samples were studied by several independent laboratories, their results were positive: the so-called anaerobic bacteria lived in the deep layers, which do not need oxygen access.
The bacteria were also found in the rocks of a gold mine in South Africa at a depth of 2.8 km, where the temperature was 60°C. They also live deep under the bottom of the oceans at temperatures above 100 °. As the Kola super-deep well showed, there are conditions for microorganisms to live even at a depth of more than 12 km, since the rocks turned out to be quite porous, saturated with aqueous solutions, and where there is water, life is possible.
Microbiologists also found colonies of bacteria in an ultra-deep well that opened the Siljan Ring crater in Sweden. It is curious that microorganisms lived in ancient granites. Although these were very dense rocks under great pressure, groundwater circulated through a system of micropores and cracks. The rock mass at a depth of 5.5-6.7 km became a real sensation. It was saturated with a paste of oil with magnetite crystals. One possible explanation for this phenomenon was given by the American geologist Thomas Gold, author of The Deep Hot Biosphere. Gold suggested that magnetite-oil paste is nothing more than a waste product of bacteria that feed on methane coming from the mantle.
As studies show, bacteria are content with truly Spartan conditions. The limits of their endurance remain a mystery, but it seems that the temperature of the interior still sets the lower limit for the habitat of bacteria. They can multiply at 110°C and withstand, albeit for a short time, temperatures of 140°C. If we consider that on the continents the temperature increases by 20-25 ° with each kilometer, then living communities can be found up to a depth of 4 km. Under the ocean floor, the temperature does not rise as quickly, and the lower limit of life can lie at a depth of 7 km.
This means that life has a colossal margin of safety. Consequently, the Earth's biosphere cannot be completely destroyed even in the event of the most serious cataclysms, and, probably, on planets devoid of an atmosphere and hydrosphere, microorganisms may well exist in the depths.
An attempt to study the geological section and the thickness of volcanic rocks emerging on the surface of the earth prompted scientific centers and, like them, research organizations to identify the origin of deep faults. The fact is that structural rock samples, previously extracted from the bowels of the Earth and the Moon, were then of equal interest for study. And the choice of the point of laying the mouth fell on the existing huge bowl-like trough, the origin of which is associated with the presence of a deep fault in the area of the Kola Peninsula.
It was believed that the Earth is a kind of sandwich, consisting of a crust, mantle and core. By this time, sedimentary rocks close to the surface had been sufficiently explored in the development of oil fields. Exploration for non-ferrous metals was rarely accompanied by drilling below the 2000-meter mark.
The Kola SG (superdeep), below a depth of 5000 meters, was supposed to find a section of granite and basalt layers. This did not happen. The drilling projectile pierced hard granite rocks up to the mark of 7000 meters. Further, the sinking went through relatively soft soils, which caused the collapse of the walls of the shaft and the formation of cavities. The crumbling soil jammed the tool head so much that when lifting the pipe string broke off, leading to an accident. The Kola well was supposed to confirm or refute these long-established teachings. In addition, scientists did not dare to indicate the intervals where exactly the boundaries between these three layers pass. The Kola well was intended for exploration and study of deposits of mineral resources, determination of patterns and gradual formation of fields of occurrence of raw material reserves. The basis was, first of all, the scientific validity of the theory of physical, hydrogeological and other parameters of the Earth's depths. And reliable information about the geological structure of the subsoil could only be provided by ultra-deep sinking of the shaft.
Meanwhile, the long-term preparation for the start of drilling operations included: the possibility of an increase in temperature as it deepens, an increase in the hydrostatic pressure of the formations, the unpredictability of the behavior of rocks, their stability due to the presence of rock and reservoir pressures.
From a technical point of view, all possible difficulties and obstacles were taken into account that could lead to a slowdown in the deepening process due to loss of time for tripping the projectile, a decrease in drilling speed due to a change in the category of rocks, and an increase in energy costs for downhole thrusters.
The most difficult factor was considered to be the constant increase in the weight of the casing and drill pipe as it went deeper.
Technical developments in the field of:
- increasing the carrying capacity, power and other characteristics of drilling equipment and equipment;
- thermal stability of the rock cutting tool;
- automation of management of all stages of the drilling process;
- processing of information coming from the bottomhole zone;
- warnings about emergencies with a drill pipe or casing string.
The sinking of an ultra-deep shaft was supposed to reveal the correctness or fallacy of the scientific hypothesis about the deep structure of the planet.
The purpose of this very costly construction was to study:
1.
Deep structure of the Pechenga nickel deposit and the crystalline base of the Baltic Shield of the peninsula. Deciphering the contour of the polymetal deposit in Pechenga, coupled with manifestations of ore bodies.
2.
The study of the nature and forces that cause the separation of the sheet boundaries of the continental crust. Identification of reservoir zones, motives and nature of high temperature formation. Determination of the physical and chemical composition of water, gases formed in cracks, pores of rocks.
3.
Obtaining exhaustive material on the material composition of rocks and information on the intervals between the granite and basalt "gaskets" of the crust. Comprehensive study of the physical and chemical properties of the extracted core.
4.
Development of advanced technical means and new technologies for sinking super-deep shafts. Possibility of application of geophysical methods of research in the zone of ore manifestations.
5.
Development and creation of the latest equipment for monitoring, testing, research, control of the drilling process.
The Kola well, for the most part, met scientific goals. The task included the study of the most ancient rocks of which the planet is composed and the knowledge of the secrets of the processes occurring in them.
Geological substantiation of drilling on the Kola Peninsula
Exploration and extraction of deposits of useful ores is always predetermined by the drilling of deep wells. And why on the Kola Peninsula and specifically in the Murmansk region, and definitely in Pechenga. The prerequisite for this was the fact that this region was considered a real pantry of mineral resources, with the richest reserves of a wide variety of ore raw materials (nickel, magnetites, apatites, mica, titanium, copper).
However, the geological calculation, made on the basis of a core from a well, revealed the absurdity of world scientific opinion. The seven-kilometer depth turned out to be composed of volcanic and sedimentary rocks (tuffs, sandstones, dolomites, breccias). Below this interval, as expected, there should have been rocks separating the granitic and basalt structures. But, alas, the basalts never appeared.
In geological terms, the Baltic Shield of the peninsula, with partial coverage of the territories of Norway, Sweden, Finland and Karelia, has been eroded and evolved for millions of centuries. Natural outbursts, destructive processes of volcanism, phenomena of magmatism, metamorphic modifications of rocks, sedimentation are most clearly imprinted on the geological record of Pechenga. This is that part of the Baltic folded shield, where the geological history of stratal and ore manifestations has evolved over billions of years.
Especially, the northern and eastern parts of the shield surface were exposed to centuries-old corrosion. As a result, glaciers, wind, water and other natural disasters, as it were, ripped off (scrapers) the upper layers of rocks.
The choice of the well site was based on the serious erosion of the upper layers and the exposure of the ancient Archean formations of the Earth. These outcrops significantly brought closer and facilitated access to the underground storerooms of nature.
Superdeep well design
Ultra-deep structures have a mandatory telescopic design. In our case, the initial diameter of the mouth was 92 cm, and the final one was 21.5.
The design guide column or the so-called conductor with a diameter of 720 mm provided for penetration to a depth of 39 linear meters. The first technical string (stationary casing), with a diameter of 324 mm and a length of 2000 meters; removable casing 245 mm, with a footage of 8770 meters. Further drilling was planned to be carried out with an open hole to the design mark. Crystalline rocks made it possible to count on the long-term stability of the uncased part of the walls. The second removable column, marked with magnetic marks, would allow continuous core sampling along the entire length of the wellbore. Radioactive markers on the downhole pipe were tuned to record the temperature of the drilling environment.
Technical equipment of a drilling rig for drilling an ultra-deep well
Drilling from scratch was carried out by the Uralmash-4E installation, that is, serial equipment used for drilling deep oil and gas wells. Up to 2000 meters, the shaft was drilled with steel drill pipes, with a turbodrill at the end. This turbine, 46 meters long, with a chisel at the end, was set in rotation under the action of a clay solution, which was pumped into the pipe at a pressure of 40 atmospheres.
Further, the sinking was carried out from an interval of 7264 meters by the domestic installation "Uralmash-15000", from an innovative point of view, a more powerful structure, with a carrying capacity of 400 tons. The complex was equipped with many technical, technological, electronic and other advanced developments.
The Kola well was equipped with a high-tech and automated structure:
1.
Exploration, with a powerful base on which the sectional tower itself is mounted, 68 meters high. Designed to implement:
- sinking of the barrel, operations of descent - lifting of the projectile and other auxiliary actions;
- retention of the leading and the entire pipe string, both on weight and during drilling;
- placement of sections (stands) of drill pipes, including collars, traveling system.
In the inner space of the tower, there were also means of the joint venture (descent - ascent), tools. It also housed the means of security and possible emergency evacuation of the rider (assistant driller).
2. Power and technological equipment, power and pump units.
3. Circulation and blowout control system, cementing equipment.
4. Automation, control, process control system.
5. Electrical supply, means of mechanization.
6. A complex of measuring equipment, laboratory equipment and much more.
In 2008, the Kola super-deep well was completely abandoned, all valuable equipment was dismantled and removed (most of it was sold for scrap).
Until 2012, the main tower of the drilling rig was dismantled.
Now only the Kola Scientific Center of the Russian Academy of Sciences is operating, which to this day is studying core extracted from an ultra-deep well.
The core itself was taken out to the city of Yaroslavl, where it is now stored.
Documentary video about the Kola Superdeep Well
New ultra-deep well records
The Kola superdeep well was considered the deepest well in the world until 2008.
In 2008, the Maersk Oil BD-04A oil well, which is 12,290 meters long, was drilled at an acute angle in the Al Shaheen oil basin.
In January 2011, this record was also broken, and it was broken by an oil well drilled in the Northern Dome (Odoptu-Sea - an oil and gas field in Russia), this well was also drilled at an acute angle to the earth's surface, the length was 12,345 meters.
In June 2013, the Z-42 well of the Chayvinskoye field again broke the depth record with a length of 12,700 meters.
