In one of the scientific programs they gave a simple example that allows you to realize how huge our planet is. Imagine a big hot air balloon. This is the whole planet. And the thinnest walls are the zone where there is life. But people have actually mastered only one layer of atoms surrounding this wall.

But humanity is constantly striving to expand its knowledge about the planet and the processes occurring on it. We launch spaceships and satellites, maintain submarines, but the hardest thing is to find out what is under our feet, inside the earth.

Wells bring relative understanding. With their help, you can find out the composition of rocks, study changes in physical conditions, and also conduct mineral exploration. And the deepest well in the world will, of course, bring the most information. The only question is where exactly it is. This is what we will try to figure out today.

OR-11

It is not surprising that the longest well was made quite recently, in 2011. New, more advanced technologies, durable and reliable materials, and accurate calculation methods made it possible to achieve this result.

Surely you will be pleased to know that it is located in Russia, and was drilled as part of the Sakhalin-1 project. All work required only 60 days, which far exceeds the results of previous surveys.

The total length of this record-breaking well is 12 kilometers 345 meters, which remains an unsurpassed record. Another achievement is the maximum length of the horizontal trunk, which is 11 kilometers 475 meters. So far no one has been able to surpass this result. But that's it for now.

BD-04A

This oil well in Qatar is famous for its record depth at that time. Its total length is 12 kilometers 289 meters, of which 10,902 meters is a horizontal trunk. By the way, it was built in 2008, and held the record for three whole years.

But this deep well is known not only for its impressive size, but also for a very sad fact. It was built next to an oil shelf for geological exploration, and in 2010 it suffered a serious accident.

This is what the well looks like now

Drilled during the USSR, the Kola superdeep well lost its title of leader in 2008. But still, it remains one of the most famous objects of this type and continues to hold third place.

Preparatory work for drilling began back in 1970. It was planned that this well would become the deepest on Earth, reaching 15 kilometers. True, such a result was never achieved. In 1992, work was suspended when the depth reached an impressive 12 kilometers 262 meters. Further research had to be stopped due to lack of funding and government support.

With its help, it was possible to obtain a lot of interesting scientific data and gain a deeper understanding of the structure of the earth’s crust. This is not surprising, since the project was initially completely scientific, not related to geological exploration or the study of mineral deposits.

By the way, the popular legend about the “well to hell” is associated with the Kola superdeep well. They say that when they reached the 11-kilometer mark, scientists heard terrifying screams. And soon after that the drill broke. According to legend, this indicates the existence of hell underground, in which sinners are tormented. It was their screams that were heard by scientists.

True, the legend does not stand up to criticism. If only because no acoustic equipment could operate at pressure and temperature at these levels. But, on the other hand, it is quite interesting to speculate that the deepest borehole will be able to reach, if not hell, then some other legendary and mythical places.

For now, they just help scientists better understand how our planet lives. And although the journey to the center of the earth is still very far away, people are clearly striving for it.

Hundreds of thousands of wells were drilled into 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 inevitably involves deep drilling. But among all these wells there is only one on the planet - the legendary Kola Superdeep (SG), the depth of which still remains unsurpassed - more than twelve kilometers. In addition, SG is one of the few that was drilled not for exploration or mining, but for purely scientific purposes: to study the most ancient rocks of our planet and learn the secrets of the processes taking place in them.

Today there is no drilling on the Kola superdeep; it was stopped in 1992. SG was not the first and not the only one in the program for studying the deep structure of the Earth. Three of the foreign wells reached a depth of 9.1 to 9.6 km. It was planned that one of them (in Germany) would surpass the Kola one. However, drilling at all three, as well as at SG, was stopped due to accidents and for technical reasons cannot yet be continued.

Apparently, it is not for nothing that the complexity of drilling ultra-deep wells is compared with a flight into space, with a long 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 geological exploration expedition (Kola Geological Exploration Expedition) was created to drill the SG. The drilling location was also, of course, not chosen by chance - the Baltic Shield in the Kola Peninsula area. Here, the oldest igneous rocks about 3 billion years old (and the Earth is only 4.5 billion years old) come to the surface. It was interesting to drill in the oldest igneous rocks, because sedimentary rocks down to a depth of 8 km have already been well studied for oil production. And during mining, they usually only penetrate 1-2 km into igneous rocks. The choice of location 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 this is where 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.

Before drilling began, a section of the earth's crust was constructed based on seismological data. It served as a forecast for the appearance of those earth layers that the well intersected. It was assumed that a granite strata extends to a depth of 5 km, after which stronger and more ancient basaltic rocks were expected.

So, the drilling site was chosen in the north-west of the Kola Peninsula, 10 km from the city of Zapolyarny, not far from our border with Norway. 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 buildings. 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 a ravine, the buildings and tall chimneys of a nickel plant are visible; behind it, along the mountainside, are dark dumps of waste rock from a nearby quarry. Near the town there is a highway to the city of Nikel and to a small lake, on the other side of which is Norway.

The soil of those places contains abundant traces of the past war. When you take a bus from Murmansk to Zapolyarny, about halfway along the 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, facing the Barents Sea. Although there were fierce battles all the time and losses on both sides were huge. The Germans unsuccessfully tried 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.

The pipe string was lowered and raised on this hook. On the left - in the basket - there are 33-meter pipes - "candles" - prepared for descent.

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 were encountered). In this section, the upper part (up to 7 km) is a Proterozoic strata with layers of volcanic (diabase) and sedimentary rocks (sandstones, dolomites). Below 7 km there is an Archean sequence with repeating units of rocks (mainly gneisses and amphibolites). Its age is 2.86 billion years. B. A well bore with many drilled and lost boreholes (below 7 km) is shaped like the branched roots of a giant plant. The well seems to be twisting because the drill is constantly deviating towards less durable rocks.

From Zapolyarny to Superglubokaya - 10 km. The road goes past the plant, then along the edge of the quarry and then climbs up the mountain. From the pass a small basin opens, in which the drilling rig is installed. Its height is as high as a twenty-story building. “Shift workers” came here from Zapolyarny for 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 could be heard from the drilling rig around the clock. The silence meant that for some reason there was a break in the drilling. In winter, during the long polar night - and it lasts there from November 23 to January 23 - the entire drilling rig glowed with lights. Often the light of the aurora was added to them.

A little about the staff. The Kola geological exploration expedition created for drilling brought together a good, highly qualified team of workers. The head of the GRE, a talented leader who selected the team, was almost always D. Guberman. Chief engineer I. Vasilchenko was responsible for drilling. The drilling rig was commanded by A. Batishchev, whom everyone simply called Lekha. Geology was in charge of V. Laney, and geophysics was in charge of Yu. Kuznetsov. A huge amount of work on processing the core and creating a core storage facility was carried out by geologist Yu. Smirnov - the same one who had the “treasured cabinet”, which we will tell you about later. More than 10 research institutes took part in conducting research on SG. The team also had its own “Kulibins” and “left-handers” (S. Tserikovsky was especially distinguished), who invented and manufactured various devices that sometimes made it possible 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

Well drilling began in 1970. Drilling to a depth of 7263 m took 4 years. It was carried out using a serial installation, which is usually used in oil and gas production. Due to constant winds and cold, the entire tower had to be covered to the top with wooden panels. Otherwise, it is simply impossible for someone who must stand at the top while lifting a pipe string to work.

Then there was a year-long break associated with the construction of a new tower and the installation of a specially designed drilling rig - Uralmash-15000. It was with its 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 column rotates, but only the drilling head. Drilling fluid was fed through the column under pressure, rotating a multi-stage turbine located below. Its total length is 46 m. ​​The turbine ends with a drill head with a diameter of 214 mm (it is often called a crown), which has a ring 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 along with the drilling fluid is carried down the well to the surface.

On the core samples on the right, oblique stripes are clearly visible, meaning that here the well passed through obliquely located formations.

The mass of the column immersed in a well with drilling fluid is about 200 tons. This is despite the fact that specially designed light alloy pipes were used. If a column is made from ordinary steel pipes, it will burst from its own weight.

Many difficulties, sometimes completely unexpected, arise in the process of drilling at great depths and with core sampling.

The penetration in one trip, determined by the wear of the drill head, is usually 7-10 m. (A trip, or cycle, is the lowering of the string with the turbine and drilling tool, the actual drilling and the complete lifting of the string.) Drilling itself takes 4 hours. And the descent and ascent of the 12-kilometer column takes 18 hours. When lifted, the column 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. This is the extent of their wear.

Up to a depth of approximately 7 km, the well intersected strong, relatively homogeneous rocks, and therefore the borehole was smooth, almost corresponding to the diameter of the drill head. The work progressed, one might say, calmly. However, at a depth of 7 km, less durable fractured rocks appeared, interbedded with small very hard layers - gneisses, amphibolites. Drilling became more difficult. The trunk took on an oval shape, and many cavities appeared. Accidents have become more frequent.

The figure shows the initial forecast of the geological section and the one compiled on the basis of drilling data. It is interesting to note (column B) that the inclination angle of the formations along the well is about 50 degrees. Thus, it is clear that the rocks intersected by the well come to the surface. This is where we can remember the already mentioned “cherished cabinet” of geologist Yu. Smirnov. There, on one side, he had samples obtained from the well, and on the other, samples taken on the surface at the distance from the drilling site where the corresponding formation comes up. The match between the breeds is almost complete.

The year 1983 was marked by a hitherto unsurpassed record: the drilling depth exceeded 12 km. Work was suspended.

The International Geological Congress was approaching, which, according to plan, was held in Moscow. The Geoexpo exhibition was being prepared for it. It was decided not only to read reports on the results achieved at the SG, but also to show the participants of the congress the work in situ 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 record depth. There were impressive graphs telling about drilling techniques and technology, extracted rock samples, photographs of equipment and staff at work. But the greatest attention of the participants and guests of the congress was attracted by one detail that was unconventional for an exhibition display: the most ordinary and already slightly rusty drill head with worn-out carbide teeth. The label stated that it was exactly what 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 at the SG next to the drilling rig there was a large pile of exactly the same already rusted drill heads: after all, they had to be replaced with new ones approximately every drilled 7-8 m.

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 actually been achieved in the Union. Such a departure took place. A section of the congress held a meeting there on site. The delegates were shown the drilling rig, where they lifted the column from the well, disconnecting 33-meter sections from it. Photos and articles about SG circulated in newspapers and magazines in almost all countries of the world. A postage stamp was issued and special cancellation of envelopes was organized. I will not list the names of laureates of various prizes and those awarded for their work...

But the holidays were over, it was necessary to continue drilling. And it began with the biggest accident on the first flight on September 27, 1984 - a “black date” in the history of the SG. The well does not forgive when it is left without attention for a long time. During the time that drilling was not carried out, changes inevitably occurred in its walls, those that were not secured with a cemented steel pipe.

At first everything went casually. The drillers carried out their usual operations: one by one they lowered sections of the drill string, connected the drilling fluid supply pipe to the last, upper one, and turned on the pumps. We started drilling. The instruments on the console in front of the operator showed the normal operating mode (number of revolutions of the drill head, its pressure on the rock, fluid flow to rotate the turbine, etc.).

Having drilled another 9-meter section at a depth of more than 12 km, which took 4 hours, we reached a depth of 12.066 km. We got ready to lift the column. We tried it. Doesn't work. “Sticking” has been observed more than once at such depths. This is when some section of the column seems to stick to the walls (maybe something fell off from above and it jammed a little). To move a column, a force exceeding its weight (about 200 tons) is required. They did the same this time, but the column did not move. We increased the force a little, and the instrument needle sharply decreased the readings. The column became much lighter; such weight loss could not have happened during the normal course of the operation. We started lifting: we unscrewed the sections one by one. During the last lift, a shortened piece of pipe with an uneven bottom edge was hanging on a hook. This meant that not only the turbo drill remained in the well, but also 5 km of drill pipes...

They tried to get them for seven months. After all, they lost not just 5 km of pipes, but the results of five years of work.

Then all attempts to recover what was lost were stopped and drilling began again from a depth of 7 km. It must be said 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 it is even more difficult. Drilling, operation of equipment and equipment are carried out at maximum speed.

Therefore, accidents can be expected here at any moment. They are preparing for them. Methods and means of their elimination are thought out in advance. A typical complex accident is the breakage of the drilling assembly along with part of the drill pipe string. The main method of eliminating it is to create a bench just above the lost part and from this place drill a new bypass shaft. A total of 12 such bypass trunks were drilled in the well. Four of them range from 2200 to 5000 m in length. The main cost of such accidents is years of lost labor.

Only in everyday life is a well 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 super-deep and intersects inclined formations of varying densities. Then it seems to squirm, because the drill constantly deviates towards less durable rocks. After each measurement showing that the well's inclination exceeds the permissible one, an attempt must be made to “put it back in place.” To do this, special “deflectors” are lowered along with the drilling tool, which help reduce the inclination angle of the well during drilling. Accidents often occur with the loss of drilling tools and parts of pipes. After this, the new trunk has to be made, as we have already said, by stepping aside. So imagine what a well looks like in the ground: something like the roots of a giant plant branching at depth.

This is the reason for the special duration of the last drilling phase.

After the largest accident - the "black date" of 1984 - they again approached a depth of 12 km only after 6 years. In 1990, the maximum was reached - 12,262 km. After several more accidents, we became convinced that we couldn’t get any deeper. All possibilities of modern technology have been exhausted. It seemed as if the Earth no longer wanted to reveal its secrets. Drilling stopped in 1992.

RESEARCH WORK. 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 well. And this task is completed. The longest core in the world was marked like a ruler into 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 all that remains is to study the core, which is truly 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 fluid. Even if you recreate deep conditions in a special chamber, the parameters measured on the sample still differ from those in the array. And one more small “hiccup”: for every 100 m of a drilled well, 100 m of core is not obtained. In the SG, from depths of more than 5 km, the average core yield 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 layers.

So, a core recovered from a borehole using SG does not provide complete information about deep-seated rocks.

The wells were drilled for scientific purposes, so the whole range of modern research methods was used. In addition to core extraction, studies of the properties of rocks in their natural occurrence were necessarily carried out. The technical condition of the well was constantly monitored. They measured the temperature throughout the wellbore, natural radioactivity - gamma radiation, induced radioactivity after pulsed neutron irradiation, electrical and magnetic properties of rocks, the speed of propagation of elastic waves, and studied the composition of gases in the well fluid.

Up to a depth of 7 km, serial devices were used. Working at greater depths and at higher temperatures required the creation of special heat- and pressure-resistant devices. Particular difficulties arose during the last stage of drilling; when the temperature in the well approached 200°C and the pressure exceeded 1000 atmospheres, serial devices could no longer work. 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 we worked only on domestic equipment.

In short, the well was explored in sufficient detail to its entire depth. Research was carried out in stages, approximately once a year, after deepening the well by 1 km. Each time after this, an assessment was made of the reliability of the materials received. The corresponding calculations made it possible to determine the parameters of a particular breed. They discovered a certain alternation of layers and already knew what rocks the caverns were associated with and the partial loss of information associated with them. We learned to literally identify rocks from “crumbs” and, on this basis, to recreate a complete picture of what the well “hidden.” In short, it was possible to construct a detailed lithological column - to show the alternation of rocks and their properties.

FROM OWN EXPERIENCE

About 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 measurements that were entrusted to me. At this time, the well was usually washed out and made available for research for a month. The time of the planned stop was always known in advance. The telegram calling for the work also arrived in advance. The equipment has been checked and packaged. 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 borehole tool developer, a developer of new ground-based equipment, and I, 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 the equipment. We are waiting for a call - a call from the well. It’s our turn to “dive” third, but if our predecessors refuse, the well will be provided to us. This time everything is fine with them, they say that they will finish by tomorrow morning. With us in the same team are geophysicists - operators who record signals received from equipment in the well and command all operations for lowering and raising downhole equipment, as well as mechanics on the hoist, they control the unwinding of those same 12 km of cable from the drum and onto it. , on which the device is lowered into the well. Drillers are also on duty.

Work has begun. The device is lowered into the well several meters. Last check. Let's 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. This means 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 turned out to be faulty. He is being replaced. This takes more than a day. The new descent took 10 hours. Finally, the person watching the signal said: “We have arrived at the eleventh kilometer.” Command to operators: “Start recording.” What and how is planned in advance according to the program. Now you need to lower and raise the downhole tool several times at a given interval to take measurements. This time the equipment worked fine. Now it's a full rise. They raised it to 3 km, and suddenly the winchman called (he is a man with humor): “The rope is over.” How?! What?! Alas, the cable broke... The downhole tool and 8 km of cable remained lying at the bottom... Fortunately, a day later the drillers were able to pick it all up, using methods and devices developed by local craftsmen to eliminate such emergencies.

RESULTS

The objectives set in the ultra-deep drilling project have been completed. Special equipment and technology for ultra-deep drilling, as well as for studying wells drilled to great depths, 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 core samples to a depth of 12,262 m.

The well gave an excellent gift to the homeland at shallow depths - in the range of 1.6-1.8 km. Industrial copper-nickel ores were opened there - a new ore horizon was discovered. And it comes in handy, because the local nickel plant is already running short of ore.

As noted above, the geological forecast of the well section did not come true (see figure on page 39.). The picture that was expected during the first 5 km in the well extended 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 greatest reflection during seismic sounding is the level where the granites transform into a more durable basalt layer. In reality, it turned out that less strong and less dense fractured rocks are located there - Archean gneisses. This was never expected. And this is fundamentally new geological and geophysical information, which allows us to interpret the data of deep geophysical research differently.

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. Thus, at depths of 9-12 km, highly porous fractured rocks were encountered, saturated with highly mineralized underground waters. 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 considered suitable for industrial development). But will it ever be profitable to mine gold from such depths?

Ideas about the thermal regime of the earth's interior and the deep distribution of temperatures in 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 flow is of radiogenic origin.

Having drilled the unique Kola superdeep 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. OSADCHY.

LITERATURE

Kola superdeep. M.: 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 villages from HABITAT

Sredao.ru townhouses from the real estate office HABITAT

The Kola superdeep well is the deepest borehole in the world (from 1979 to 2008). It is located in the Murmansk region, 10 kilometers west of the city of Zapolyarny, on the territory of the geological Baltic shield. Its depth is 12,262 meters. Unlike other ultra-deep wells that were made for oil production or geological exploration, SG-3 was drilled solely to study the lithosphere in the place where the Mohorovicic boundary is. (abbreviated Moho boundary) is the lower boundary of the earth’s crust, at which there is an abrupt increase in the velocities of longitudinal seismic waves.

The Kola superdeep well was laid in honor of the 100th anniversary of Lenin’s birth, in 1970. Sedimentary rock strata by that time had been well studied during oil production. It was more interesting to drill where volcanic rocks about 3 billion years old (for comparison: the age of the Earth is estimated at 4.5 billion years) come to the surface. To extract minerals, such rocks are rarely drilled deeper than 1-2 km. It was assumed that already at a depth of 5 km the granite layer would be replaced by a basalt one. On June 6, 1979, the well broke the record of 9583 meters, previously held by the Bertha-Rogers well (an oil well in Oklahoma). In the best years, 16 research laboratories worked at the Kola superdeep well, they were personally supervised by the Minister of Geology of the USSR.

Although it was expected that a clear boundary between granites and basalts would be discovered, only granites were found in the core throughout the entire depth. However, due to the high pressure, the compressed granites greatly changed their physical and acoustic properties. As a rule, the lifted core crumbled from active gas release into slurry, since it could not withstand a sharp change in pressure. It was possible to remove a strong piece of core only with a very slow lifting of the drill, when the “excess” gas, still pressed to high pressure, managed to escape from the rock. The density of cracks at great depths, contrary to expectations, increased. There was also water at depth that filled the cracks.

It is interesting that when the International Geological Congress was held in Moscow in 1984, at which the first results of research on the well were presented, many scientists jokingly suggested burying it immediately, since it destroys all ideas about the structure of the earth’s crust. Indeed, strange things began even in the first stages of penetration. For example, theorists, even before the start of drilling, promised that the temperature of the Baltic shield would remain relatively low to a depth of at least 5 kilometers, the ambient temperature exceeded 70 degrees Celsius, at seven - over 120 degrees, and at a depth of 12 it was hot stronger than 220 degrees - 100 degrees higher than predicted. Kola drillers questioned the theory of the layered structure of the earth's crust - at least in the interval up to 12,262 meters.

“We have the deepest hole in the world - so we must use it!” - David Guberman, the permanent director of the Kola Superdeep Research and Production Center, exclaims bitterly. In the first 30 years of the Kola Superdeep, Soviet and then Russian scientists broke through to a depth of 12,262 meters. But since 1995, drilling has been stopped: there was no one to finance the project. What is allocated within the framework of UNESCO's scientific programs is only enough to maintain the drilling station in working condition and study previously extracted rock samples.

Huberman recalls with regret how many scientific discoveries took place at the Kola Superdeep. Literally every meter was a revelation. The well showed that almost all of our previous knowledge about the structure of the earth's crust is incorrect. It turned out that the Earth is not at all like a layer cake.

Another surprise: life on planet Earth turns out to have arisen 1.5 billion years earlier than expected. At depths where it was believed that there was no organic matter, 14 species of fossilized microorganisms were discovered - the age of the deep layers exceeded 2.8 billion years. At even greater depths, where there are no longer sediments, methane appeared in huge concentrations. This completely and completely destroyed the theory of the biological origin of hydrocarbons such as oil and gas. There were almost fantastic sensations. When, in the late 70s, the Soviet automatic space station brought 124 grams of lunar soil to Earth, researchers at the Kola Science Center found that it was like two peas in a pod to samples from a depth of 3 kilometers. And a hypothesis arose: the Moon broke away from the Kola Peninsula. Now they are looking for where exactly. By the way, the Americans, who brought half a ton of soil from the Moon, did nothing meaningful with it. They were placed in airtight containers and left for research by future generations.

Quite unexpectedly for everyone, Alexei Tolstoy’s predictions from the novel “Engineer Garin’s Hyperboloid” were confirmed. At a depth of over 9.5 kilometers, a real treasure trove of all kinds of minerals, in particular gold, was discovered. A real olivine layer, brilliantly predicted by the writer. It contains 78 grams of gold per ton. By the way, industrial production is possible at a concentration of 34 grams per ton. But, what is most surprising, at even greater depths, where there are no longer sedimentary rocks, natural methane gas was found in huge concentrations. This completely and completely destroyed the theory of the biological origin of hydrocarbons such as oil and gas

Not only scientific sensations were also associated with the Kola well, but also mysterious legends, most of which turned out to be fictions of journalists when verified. According to one of them, the primary source of information (1989) was the American television company Trinity Broadcasting Network, which, in turn, took the story from a report by a Finnish newspaper. Allegedly, when drilling a well, at a depth of 12 thousand meters, the scientists' microphones recorded screams and moans.) Journalists, without even thinking that it was simply impossible to insert a microphone to such a depth (what kind of sound recording device can work at temperatures above two hundred degrees?) wrote that the drillers heard a “voice from the underworld.”

After these publications, the Kola superdeep well began to be called “the road to hell,” claiming that every new kilometer drilled brought misfortune to the country. They said that when the drillers were drilling the thirteenth thousand meters, the USSR collapsed. Well, when the well was drilled to a depth of 14.5 km (which actually did not happen), they suddenly came across unusual voids. Intrigued by this unexpected discovery, the drillers sent down a microphone capable of operating at extremely high temperatures and other sensors. The temperature inside allegedly reached 1,100 °C - there was the heat of fiery chambers, in which human screams could allegedly be heard.

This legend still roams the vast expanses of the Internet, having outlived the very culprit of these gossips - the Kola well. Work on it was stopped back in 1992 due to lack of funding. Until 2008, it was in a mothballed state. A year later, the final decision was made to abandon the continuation of research and to dismantle the entire research complex and “bury” the well. The final abandonment of the well occurred in the summer of 2011.
So, as you can see, this time scientists were not able to get to the mantle and examine it. However, this does not mean that the Kola well did not give anything to science - on the contrary, it turned all their ideas about the structure of the earth’s crust upside down.

RESULTS

The objectives set in the ultra-deep drilling project have been completed. Special equipment and technology for ultra-deep drilling, as well as for studying wells drilled to great depths, 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 core to a depth of 12,262 m. The well gave an excellent gift to the homeland at shallow depths - in the range of 1.6-1. 8 kilometers. Industrial copper-nickel ores were opened there - a new ore horizon was discovered. And it comes in handy, because the local nickel plant is already running short of ore.

As noted above, the geological forecast of the well section did not come true. The picture that was expected during the first 5 km in the well extended 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 greatest reflection during seismic sounding is the level where the granites transform into a more durable basalt layer. In reality, it turned out that less strong and less dense fractured rocks are located there - Archean gneisses. This was never expected. And this is fundamentally new geological and geophysical information, which allows us to interpret the data of deep geophysical research differently.

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. Thus, at depths of 9-12 km, highly porous fractured rocks were encountered, saturated with highly mineralized underground waters. 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 considered suitable for industrial development). But will it ever be profitable to mine gold from such depths?

Ideas about the thermal regime of the earth's interior and the deep distribution of temperatures in 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 flow is of radiogenic origin.

The depths of the earth contain as many mysteries as the vast expanses of the Universe. This is exactly what some scientists think, and they are partly right, because people still don’t know exactly what is under our feet, deep underground. Over the entire existence of earthly civilization, we have been able to go deeper into the planet a little more than 10 kilometers. This record was set back in 1990 and lasted until 2008, after which it was updated several times. In 2008, Maersk Oil BD-04A, a 12,290 meter long inclined oil well, was drilled (Al Shaheen oil basin in Qatar). In January 2011, an inclined oil well with a depth of 12,345 meters was drilled at the Odoptu-Sea field (Sakhalin-1 project). The record for drilling depth currently belongs to the Z-42 well of the Chayvinskoye field, the depth of which is 12,700 meters.

What is stopping you from drilling a well to the center of the Earth and finding out what is there? We know much more about the structure of space than about how the Earth works. Although attempts to penetrate deep into the Earth have been made more than once. The first two ultra-deep wells were drilled in the state of Louisiana in North America. Project managers equipped the well with meter-diameter casing pipes extending to a depth of 1 km, with three powerful automatic emergency valves. A special concrete plant was located next to the drilling rig, which in the event of an accident would supply a quick-hardening solution into the casing pipe. Up to a depth of 9 km, mining proceeded as usual. But deeper down they encountered increasing internal pressure, and hydrogen sulfide began to be released from the well. The drillers joked that they had drilled to hell. From a depth of 9.6 km, molten sulfur came out of the well, and the miners began to lose consciousness. The emergency shutters closed. And the concrete plant provided the supply of special solution to the o! casing pipe, and the well was plugged.

In the USSR they also tried to drill several ultra-deep wells, but domestic drillers suffered the same sad fate. While drilling the Kumzha-9 well on the Pechora River in the Arkhangelsk region, a powerful fountain of gas, oil and drilling fluid unexpectedly erupted from a depth of 7 km. So much so that the drill simply “flew” into the zone of abnormally high reservoir pressure. Pipes from the drilling rig scattered like pasta from a pan. A torch 150 meters high immediately hit. We tried to extinguish the torch with tanks, but it was unsuccessful. The fountain hummed like a jet engine. As a result, it was only possible to extinguish it with the help of underground nuclear explosions. To do this, an inclined well was drilled towards the emergency shaft. They brought a nuclear mine over it and detonated it at a depth of 1.5 km. An underground chamber was formed, and a zone of lateral pressure blocked the wellbore.

The ultra-deepest well - SGS-3 with a depth of 12.3 km - was drilled on the Kola Peninsula near the village of Nikel. The work was carried out by a special institute of geophysics with a total number of employees of 5,000 people, and 520 people worked at the mine itself during the Soviet years. The estimated drilling depth was set at 30 km. Up to 7 km drilling proceeded as usual. The surprises began at a depth of 7.5 km, the temperature where the drill was in direct contact with the basalt rose to 100 ° C, and the density of the samples raised to the surface decreased by 20%. Geochemists discovered various gases in the rock - hydrogen and helium, and biologists - unknown bacteria. These bacteria, extracted into an oxygen atmosphere, died, and therefore they were called aerophobic (afraid of air). Suddenly the drill jammed tightly, then they began sinking the second shaft. At a depth of 8 km, the temperature rose to 120°C, the cores became porous, and the number of bacteria increased. Conventional steel pipes were replaced with! new ones, made of high-strength steel, the drill was made of molybdenum, the diamond grains were replaced with the artificial material elbor, which was superior to diamond in fire resistance, strength and hardness. Finally, the wellbore reached a depth of 12,240 m. The drill jammed again and the machine went silent.

A little about the characteristics of the drilling rig (Uralmash-15000). The drill string below 2000 meters was assembled with pipes made of light aluminum alloys (steel would simply burst from its weight). The weight of the column is about 200 tons.

Turbodrill - a turbine 46 meters long, operating from the pressure of the drilling fluid, rotates the drill bit (bit).

A core receiver is a removable pipe inside a turbodrill that is used for collecting rock samples (core).

Conventional carbide drill bits were used. One bit lasts approximately 4 hours, during which time it is possible to drill 7-10 meters. It takes up to 18 hours to lower and raise the column. In this case, the column is disassembled into sections of several pipes.

The first 7 kilometers are composed of volcanic and sedimentary rocks: tuffs, basalts, breccias, sandstones, dolomites. Deeper lies the so-called Conrad section, after which the speed of seismic waves in the rocks increases sharply, which was previously interpreted as the boundary between granites and basalts. This section at the Kola well was passed a long time ago, but the basalts of the lower layer of the earth’s crust never appeared anywhere. On the contrary, granites and gneisses began to appear.

The Kola well section disproved the two-layer model of the earth's crust, according to which, under the granitoid crust of the continents, there should be a basaltic crust in which the continents, according to the theory of plate tectonics, move along the surface of the planet. Seismic sections in the interior of the planet turned out to be not the boundaries of layers of rocks of different compositions. Rather, they indicate a change in the properties of the stone with depth. The sample raised to the surface from a 12-kilometer depth turned out to be not basalt, as expected by theory, but granite.

Previously, it was thought that with distance from the earth's surface and increasing pressure, rocks become more monolithic and the number of cracks in them decreases. But the well showed the opposite - starting from 9 km, the strata turned out to be very porous and literally stuffed with cracks through which aqueous solutions circulated. At depth, the temperature turned out to be higher than expected: +80°C. At the 7 km mark the temperature in the face was 120°C, and at 12 km – +230°C. Scientists discovered gold mineralization in samples from the Kola well. Insertion of the precious metal was found in ancient rocks at a depth of 9.5–10.5 km (an average of 37.7 mg of gold per ton of rock).

How many scientific discoveries have taken place at the Kola Superdeep Well! Literally every meter was a revelation. The well showed that almost all of our previous knowledge about the structure of the earth's crust is incorrect. It turned out that the Earth is not at all like a layer cake. Up to 4 kilometers everything went according to theory, and then the end of the world began - theorists promised that the temperature of the Baltic Shield would remain relatively low to a depth of at least 15 kilometers. Accordingly, it will be possible to dig a well up to almost 20 kilometers, just up to the mantle. But already at 5 kilometers the ambient temperature exceeded 70°C, at seven - over 120, and at a depth of 12 km it was hotter than 220°C, which is 100° higher than predicted by theorists! The results cast doubt on the theory of the layered structure of the earth's crust - at least up to 12,262 meters.

At school we were taught: there are young rocks, granites, basalts, mantle and core. But the granites turned out to be 3 kilometers lower than expected. No basalts were found at all. All drilling took place in the granite layer. But all our ideas about the origin and distribution of minerals are connected with the theory of the layered structure of the Earth. At depths where it was believed that there was no organic matter, 14 species of microorganisms were discovered - the age of the deep layers exceeded 2.8 billion years. At even greater depths, where there are no longer sediments, methane appeared in huge concentrations. This completely destroyed the theory of the biological origin of hydrocarbons such as oil and gas.

Quite unexpectedly for everyone, Alexei Tolstoy’s predictions from the novel “Engineer Garin’s Hyperboloid” were confirmed. At a depth of over 9.5 kilometers, they discovered a real storehouse of all kinds of minerals, in particular gold - a real olivine layer, brilliantly predicted by the writer.

Problems at a German ultra-deep well in the south-east of Bavaria, founded on the remains of an ancient mountain range 300 million years old, began after reaching a depth of 7 km: at the end of the work, the face deviated from the vertical by 300 m. Just like at Kola, it was necessary drill new shafts. The temperature in the well at a depth was 270°C, and this forced the work to be stopped without achieving the cherished goal. At the maximum depth for drilling, there were mainly amphibolites and gneisses - ancient metamorphic rocks. No zones of transition from granitoid crust to gneiss were found here either.

In the United States, deep drilling of the ocean floor continues in zones of volcanic and tectonic activity in 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 birth to these islands. They planned to drill a well at the foot of the Mauna Kea volcano to a depth of 4.5 km, but due to the extreme temperatures they could only drill 3 km. Another project is a deep observatory on the San Andreas Fault. Drilling a well through this fault of the North American continent began in June 2004 and covered 2 of the 3 planned kilometers. Already, oil and gas production in the United States from depths of 6–7 km has become commonplace. The Tyumen superdeep well showed that 7 kilometers from the surface there are rock strata that are promising for gas fields.

One of the most amazing discoveries made through drilling is the existence 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 underground kingdom, seemingly completely unsuitable for existence. Enormous pressures, high temperatures, lack of oxygen and living space - nothing could become an obstacle to the spread of life in the depths of the lithosphere. According to some estimates, the mass of microorganisms living underground may even exceed the mass of all living creatures inhabiting the surface of our planet.

At the beginning of the 20th century, American scientist Edson Bastin discovered bacteria in water from an oil-bearing horizon from a depth of several hundred meters. The microorganisms that lived 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 then - they simply did not believe in it. At that time it was believed that life was just a thin film on the surface of the planet.

In 1980, the US Department of Energy was looking for safe methods for disposing of radioactive waste. For these purposes, it was supposed to use mines in impenetrable rocks, where bacteria feeding on radionuclides live. In 1987, deep drilling of several wells began in South Carolina. Samples were taken from a depth of half a kilometer and further into the depths, while taking all possible precautions so as not to introduce bacteria and air from the surface of the Earth. Several independent laboratories studied the samples, their results showed that the deep layers were inhabited by anaerobic bacteria that do not require oxygen.

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 ocean floor at temperatures above 100°. As the Kola superdeep well showed, there are conditions for microorganisms to live even at a depth of more than 12 km, since rocks at great depths turned out to be porous, saturated with aqueous solutions.

In an ultra-deep well that opened the Siljan Ring crater in Sweden, microbiologists also discovered colonies of bacteria. It is curious that microorganisms lived in ancient granites. Although these were very dense rocks lying under high pressure, underground, apparently juvenile, waters circulated in them through a system of micropores and cracks. American geologist Thomas Gold believes that magnetite-oil paste at a depth of 4–5 km is nothing more than a product of the vital activity of bacteria that feed on methane coming from the mantle.

The endurance limits of lithospheric bacteria are amazing, but it seems that the lower limit of their habitat is still set by the temperature of the subsoil. They can reproduce at 110°C and can withstand temperatures of 140°C, albeit for a short time. Under the ocean floor, temperatures do not rise as quickly, and the lower limit of life there may lie at a depth of 7 km. This means that the Earth’s biosphere cannot be completely destroyed even in the event of the most serious cataclysms, and on planets without an atmosphere and hydrosphere, microorganisms may well exist in the depths.

Katrina Edwards and her colleagues discovered that exposed hard rock at the bottom of deep ocean trenches harbors 3 to 4 times more bacteria than the ocean's aquatic environment. Life can exist in cold, dark, rocky environments, Santelli says: "However, we did not expect to find such an abundance of microbial life at great depths." Amazed by the presence of a huge diversity of microorganisms, the researchers concluded that rich microbial life was present throughout the surface of the ocean floor. The discovery supports the theory that bacteria survive on endogenous energy coming from deep within the Earth - "a process that will greatly add to our knowledge of the deep carbon cycle and the development of life on earth," says Katrina Edwards.

To date, there are several dozen ultra-deep wells in the world. Here are the most famous of them: Bertha Rogers, USA, - 9,583 m. Beiden Unit, USA, - 9,159 m. KTV Hauptbohrung, Germany - 9,100 m. University, USA - 8,686 m. Zisterdorf, Austria - 8 553 m. Bighorn, USA, Wyoming - 7,583 m. Siljan Ring, Sweden - 6,800 m. The only deeper than the Kola (and not much at all) is the Odoptu well, drilled by Exxon Neftegas Limited (ENL) at the end of 2010 - beginning of 2011 (depth 12,345 m) and a well drilled by Transocean for Maersk Oil in 2008 in Qatar, in the Al Shaheen oil basin, depth 12,289 meters.

Ultra-deep drilling made it possible to look into the depths 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 incorrect, as did the point of view about dry subsoil. This was first discovered during the drilling of the Kola superdeep well. Other wells in ancient crystalline strata confirmed the fact that at many kilometers deep, rocks are broken by cracks and penetrated by numerous pores, and aqueous solutions (in science called supercritical fluids) move quite freely under pressure of several hundred atmospheres. Given the information about the state of the subsoil obtained during ultra-deep drilling, projects to create radioactive waste repositories in deep ocean trenches now look very risky. According to the theory of tectonic plates, in the place of these trenches the oceanic plate is “slipped” under the continental one, and then! Radioactive waste deposited in such a trench in containers would also have to be “slipped” under the continental plate and thus buried at a considerable depth. But it turned out that in fact, no slabs in the gutters fit under each other.

Today, humankind's scientific research has reached the boundaries of the solar system: we have landed spacecraft on planets, their satellites, asteroids, comets, sent missions to the Kuiper belt and crossed the heliopause boundary. With the help of telescopes, we see events that took place 13 billion years ago - when the Universe was only a few hundred million years old. Against this background, it is interesting to evaluate how well we know our Earth. The best way to find out its internal structure is to drill a well: the deeper, the better. The deepest well on Earth is the Kola Superdeep Well, or SG-3. In 1990, its depth reached 12 kilometers 262 meters. If we compare this figure with the radius of our planet, it turns out that this is only 0.2 percent of the way to the center of the Earth. But even this was enough to change ideas about the structure of the earth’s crust.

If you imagine a well as a shaft through which you can descend by elevator into the very depths of the earth, or at least a couple of kilometers, then this is not at all the case. The diameter of the drilling tool with which engineers created the well was only 21.4 centimeters. The upper two-kilometer section of the well is a little wider - it was expanded to 39.4 centimeters, but still there is no way for a person to get there. To imagine the proportions of the well, the best analogy would be a 57-meter sewing needle with a diameter of 1 millimeter, slightly thicker at one end.

Well diagram

But this representation will also be simplified. During drilling, several accidents occurred at the well - part of the drill string ended up underground without the ability to extract it. Therefore, the well was started anew several times, from marks of seven and nine kilometers. There are four large branches and about a dozen small ones. The main branches have different maximum depths: two of them cross the 12-kilometer mark, two more do not reach it by only 200-400 meters. Note that the depth of the Mariana Trench is one kilometer less - 10,994 meters relative to sea level.

Horizontal (left) and vertical projections of SG-3 trajectories

Yu.N. Yakovlev et al. / Bulletin of the Kola Scientific Center of the Russian Academy of Sciences, 2014

Moreover, it would be a mistake to perceive the well as a plumb line. Due to the fact that rocks have different mechanical properties at different depths, the drill deviated towards less dense areas during the work. Therefore, on a large scale, the profile of the Kola Superdeep looks like a slightly curved wire with several branches.

Approaching the well today, we will see only the upper part - a metal hatch screwed to the mouth with twelve massive bolts. The inscription on it was made with an error, the correct depth is 12,262 meters.

How was a super-deep well drilled?

To begin with, it should be noted that the SG-3 was originally conceived specifically for scientific purposes. The researchers chose for drilling a place where ancient rocks - up to three billion years old - came to the surface of the earth. One of the arguments during exploration was that young sedimentary rocks were well studied during oil production, and no one had ever drilled deep into ancient layers. In addition, there were large copper-nickel deposits, the exploration of which would be a useful addition to the scientific mission of the well.

Drilling began in 1970. The first part of the well was drilled with a serial Uralmash-4E rig - it was usually used for drilling oil wells. Modification of the installation made it possible to reach a depth of 7 kilometers 263 meters. It took four years. Then the installation was changed to Uralmash-15000, named after the planned depth of the well - 15 kilometers. The new drilling rig was designed specifically for the Kola superdeep: drilling at such great depths required serious modification of equipment and materials. For example, the weight of the drill string alone at a depth of 15 kilometers reached 200 tons. The installation itself could lift loads of up to 400 tons.

The drill string consists of pipes connected to each other. With its help, engineers lower the drilling tool to the bottom of the well, and it also ensures its operation. At the end of the column, special 46-meter turbodrills were installed, driven by the flow of water from the surface. They made it possible to rotate the rock crushing tool separately from the entire column.

The bits with which the drill string bit into the granite evoke futuristic parts from a robot - several rotating spiked disks connected to a turbine on top. One such bit was enough for only four hours of work - this approximately corresponds to a passage of 7-10 meters, after which the entire drill string must be lifted, disassembled and then lowered again. The constant descents and ascents themselves took up to 8 hours.

Even the pipes for the column in the Kola Superdeep Pipe had to be used in unusual ways. At depth, temperature and pressure gradually increase, and, as engineers say, at temperatures above 150-160 degrees, the steel of serial pipes softens and is less able to withstand multi-ton loads - because of this, the likelihood of dangerous deformations and column breakage increases. Therefore, the developers chose lighter and heat-resistant aluminum alloys. Each of the pipes had a length of about 33 meters and a diameter of about 20 centimeters - slightly narrower than the well itself.

However, even specially developed materials could not withstand drilling conditions. After the first seven-kilometer section, further drilling to the 12,000-meter mark took almost ten years and more than 50 kilometers of pipes. Engineers were faced with the fact that below seven kilometers the rocks became less dense and fractured - viscous for the drill. In addition, the wellbore itself distorted its shape and became elliptical. As a result, the column broke several times, and, unable to lift it back, the engineers were forced to concrete the branch of the well and drill the shaft again, losing years of work.

One of these major accidents forced drillers in 1984 to concrete a branch of the well that reached a depth of 12,066 meters. Drilling had to start again from the 7-kilometer mark. This was preceded by a pause in work with the well - at that moment the existence of SG-3 was declassified, and the international geological congress Geoexpo was held in Moscow, whose delegates visited the site.

According to eyewitnesses of the accident, after work resumed, the column drilled a hole another nine meters down. After four hours of drilling, the workers prepared to lift the column back, but it “didn’t work.” The drillers decided that the pipe was “stuck” somewhere to the walls of the well, and increased the lifting power. The load has decreased sharply. Gradually dismantling the column into 33-meter candles, the workers reached the next section, ending with an uneven lower edge: the turbo drill and another five kilometers of pipes remained in the well; they could not be lifted.

The drillers managed to reach the 12-kilometer mark again only in 1990, at which time the diving record was set - 12,262 meters. Then a new accident occurred, and since 1994, work on the well was stopped.

Superdeep Scientific Mission

Picture of seismic tests at SG-3

“Kola Superdeep” Ministry of Geology of the USSR, Nedra Publishing House, 1984

The well was studied using a whole range of geological and geophysical methods, ranging from core collection (a column of rocks corresponding to given depths) to radiation and seismological measurements. For example, the core was taken using core receivers with special drills - they look like pipes with jagged edges. In the center of these pipes there are 6-7 centimeter holes where the rock falls.

But even with this seemingly simple (except for the need to lift this core from many kilometers deep) difficulties arose. Because of the drilling fluid, the same one that set the drill in motion, the core became saturated with liquid and changed its properties. In addition, conditions in the depths and on the surface of the earth are very different - the samples cracked due to pressure changes.

At different depths, the core yield varied greatly. If at five kilometers from a 100-meter segment one could count on 30 centimeters of core, then at depths of more than nine kilometers, instead of a rock column, geologists received a set of washers made of dense rock.

Microphotograph of rocks recovered from a depth of 8028 meters

“Kola Superdeep” Ministry of Geology of the USSR, Nedra Publishing House, 1984

Studies of material recovered from the well have led to several important conclusions. Firstly, the structure of the earth's crust cannot be simplified to a composition of several layers. This was previously indicated by seismological data - geophysicists saw waves that seemed to be reflected from a smooth boundary. Studies at SG-3 have shown that such visibility can also occur with a complex distribution of rocks.

This assumption affected the design of the well - scientists expected that at a depth of seven kilometers the shaft would enter basalt rocks, but they did not meet even at the 12-kilometer mark. But instead of basalt, geologists discovered rocks that had a large number of cracks and low density, which could not be expected at all from many kilometers deep. Moreover, traces of underground water were found in the cracks - it was even suggested that they were formed by a direct reaction of oxygen and hydrogen in the thickness of the Earth.

Among the scientific results there were also applied ones - for example, at shallow depths, geologists found a horizon of copper-nickel ores suitable for mining. And at a depth of 9.5 kilometers, a layer of geochemical gold anomaly was discovered - micrometer-sized grains of native gold were present in the rock. Concentrations reached up to a gram per ton of rock. However, it is unlikely that mining from such depths will ever be profitable. But the very existence and properties of the gold-bearing layer made it possible to clarify the models of mineral evolution - petrogenesis.

Separately, we should talk about studies of temperature gradients and radiation. For this kind of experiments, downhole instruments are used, lowered on wire ropes. The big problem was to ensure their synchronization with ground-based equipment, as well as to ensure operation at great depths. For example, difficulties arose with the fact that the cables, with a length of 12 kilometers, stretched by about 20 meters, which could greatly reduce the accuracy of the data. To avoid this, geophysicists had to create new methods for marking distances.

Most commercial instruments were not designed to operate in the harsh conditions of the lower levels of the well. Therefore, for research at great depths, scientists used equipment developed specifically for the Kola Superdeep.

The most important result of geothermal research is much higher temperature gradients than expected. Near the surface, the rate of temperature increase was 11 degrees per kilometer, to a depth of two kilometers - 14 degrees per kilometer. In the interval from 2.2 to 7.5 kilometers, the temperature increased at a rate approaching 24 degrees per kilometer, although existing models predicted a value one and a half times lower. As a result, already at a depth of five kilometers, the instruments recorded a temperature of 70 degrees Celsius, and by 12 kilometers this value reached 220 degrees Celsius.

The Kola superdeep well turned out to be unlike other wells - for example, when analyzing the heat release of rocks of the Ukrainian crystalline shield and Sierra Nevada batholiths, geologists showed that heat release decreases with depth. In SG-3, on the contrary, it grew. Moreover, measurements have shown that the main source of heat, providing 45-55 percent of the heat flow, is the decay of radioactive elements.

Despite the fact that the depth of the well seems colossal, it does not reach even a third of the thickness of the earth’s crust in the Baltic Shield. Geologists estimate that the base of the earth's crust in this area runs approximately 40 kilometers underground. Therefore, even if SG-3 reached the planned 15-kilometer cutoff, we still would not have reached the mantle.

This is the ambitious task that American scientists set for themselves when developing the Mohol project. Geologists planned to reach the border of Mohorovicic - an underground region where there is a sharp change in the speed of propagation of sound waves. It is believed to be associated with the boundary between the crust and the mantle. It is worth noting that the drillers chose the ocean floor near the island of Guadalupe as the location for the well - the distance to the border was only a few kilometers. However, the depth of the ocean itself reached 3.5 kilometers here, which significantly complicated drilling operations. The first tests in the 1960s allowed geologists to drill wells only to 183 meters.

Recently it became known about plans to resurrect the deep ocean drilling project with the help of the research drilling vessel JOIDES Resolution. Geologists chose a point in the Indian Ocean, not far from Africa, as a new target. The depth of the Mohorovicic boundary there is only about 2.5 kilometers. In December 2015 - January 2016, geologists managed to drill a well 789 meters deep - the fifth largest underwater well in the world. But this value is only half of what was required at the first stage. However, the team plans to return and finish what they started.

***

0.2 percent of the path to the center of the Earth is not that impressive compared to the scale of space travel. However, it should be taken into account that the border of the Solar system does not pass along the orbit of Neptune (or even the Kuiper belt). The Sun's gravity prevails over stellar gravity up to distances of two light years from the star. So if you carefully calculate everything, it turns out that Voyager 2 flew only a tenth of a percent of the path to the outskirts of our system.

Therefore, we should not be upset by how poorly we know the “insides” of our own planet. Geologists have their own telescopes - seismic research - and their own ambitious plans to conquer the subsoil. And if astronomers have already managed to touch a significant part of the celestial bodies in the solar system, then for geologists the most interesting things are still ahead.

Vladimir Korolev