<p>The only reasonable hypothesis is that it is filled with whatever it was filled with when the well was sealed. </p>

<p>A 12km long pipe with a sealed end is not going to have its contents replaced with something else easily. You could theorise that an intrusion of gas at the bottom opening of the pipe could expel liquid by replacement - possible, but slow.</p>

CC BY-SA 4.0
2019-05-06T13:17:28.553Z
I was hoping for something like giant ants from the center of the Earth, or red-hot magma.
uhoh
CC BY-SA 4.0
2019-05-06T13:19:46.470Z
Heh - I'm with you on this - I always dreamt it would be like opening a plug, and lava emptying from the bowels of the earth.
Rory Alsop
CC BY-SA 4.0
2019-05-06T13:15:27.460Z
2019-05-06T13:15:27.460Z
Rory Alsop
<p>During the drilling, the hole was filled with &quot;drilling mud&quot;, which served to lubricate the bit, carry the cuttings to the surface and power the bit via a turbine.</p>
<blockquote>
<p>When  the  well  reaches  a highest  depth,  there  is  a  significant  difference between  the  hydrostatic  pressure of the mud column and the lithostatic pressure due to the weight of the rocks. As a result, the walls of
the  well  can  be  destroyed (bend  in),  which leads  to  serious  complications  during drilling.  In  order  to  balance the rock pressure, there is an increase of density of the drilling mud to about 2 g per centimeter cubic.</p>
</blockquote>
<p><a href="https://iopscience.iop.org/article/10.1088/1755-1315/459/5/052066/pdf" rel="nofollow noreferrer">Application of Superdeep Drilling Technology for Study of the Earth Crust, O V Savenok et al 2020</a></p>
<p>I expect they would not have gone to the expense of pumping out the mud (if even possible) as it would result in the hole caving in.</p>

CC BY-SA 4.0
2021-09-03T16:18:01.120Z
The hole very likely collapsed whether not not there was mud in it . Collapse resistance depends on the collapse strength of the casing.
blacksmith37
CC BY-SA 4.0
2021-09-05T08:52:17.357Z
You have to pump out the mud, and all the cuttings resulting from the borehole drilling, otherwise your bit will get stuck. Plus, it was a scientific borehole, so the goal was to perform some study at depth.
In fact, mud and resulting cuttings were brought to the surface (see page 5 of this report https://iopscience.iop.org/article/10.1088/1755-1315/459/5/052066/pdf )
EarlGrey
CC BY-SA 4.0
2021-09-05T16:28:21.657Z
@EarlGrey  The mud and cuttings were brought up to the surface by pumping more (filtered) mud down the drill pipe. They would not be able to pump all the mud out of the hole (if that is what you are saying) with the equipment described.
Keith McClary
CC BY-SA 4.0
2021-09-08T08:48:22.133Z
You are right, in principle the mud at the bottom of the borehole would have a pressure of max ~240MPa (2g/cm3, times g times 12 km) ... unlikely to flush it out with N2 (or other gas) injection.
EarlGrey
CC BY-SA 4.0
2021-09-03T02:31:24.700Z
2021-09-03T02:48:24.587Z
2021-09-03T02:48:24.587Z
Keith McClary
<p>Water has likely seeped in to the point of filling the hole up to sea level along with a high concentration of mineral deposits as a suspension of solids with the <a href="https://www.atlasobscura.com/places/kola-superdeep-borehole?mc_cid=69025636df&amp;mc_eid=34be11d5e3" rel="nofollow noreferrer">180° Celsius bottom</a> creating a lava lamp like movement of those solids as they cool near the surface. Also assuming they left the drill and shafts inside, a whole lot of rusting metal.</p>

CC BY-SA 4.0
2020-03-25T03:08:41.613Z
Welcome to Stack Exchange and thanks for your answer! I don't doubt that something like this is correct. In Stack Exchange it's important to include supporting links or sources for at least some aspects of answers (even though [this answer](https://earthscience.stackexchange.com/a/16882/6031) didn't). Is it possible to add for example something about how you arrived at the 180° C figure? Thanks!
uhoh
CC BY-SA 4.0
2021-08-28T20:33:08.903Z
Not so much rust as there is no continuous source for oxygen. they would not have left the drill string ( unless a big problem) . But the casing strings will be roughly one inch thick (25 mm) thick. Drill strings are normally leased and returned.
blacksmith37
CC BY-SA 4.0
2020-03-25T02:20:44.700Z
2022-08-30T00:27:46.800Z
2022-08-30T00:27:46.800Z
Phillip C Niethe
<p>The BBC News article <a href="http://www.bbc.com/future/story/20190503-the-deepest-hole-we-have-ever-dug" rel="nofollow noreferrer">The Deepest Hole we have Ever dug</a> says:</p>
<blockquote>
<p>This is the Kola Superdeep Borehole, the deepest man made hole on Earth and deepest artificial point on Earth. The 40,230ft-deep (12.2km) construction is so deep that locals swear you can hear the screams of souls tortured in hell. It took the Soviets almost 20 years to drill this far, but the drill bit was still only about one-third of the way through the crust to the Earth’s mantle when the project came grinding to a halt in the chaos of post-Soviet Russia.</p>
</blockquote>
<p>The first image below shows the top of the Kola Superdeep Borehole, and the caption says that it is welded shut.</p>
<p>Is there any way to form a reasonable hypothesis what would happen if it were opened today? Would the 12 km deep well have filled with water, or helium, or natural gas, or is it likely to be filled with air? Would it be under tremendous pressure on the other side of the bolted-down cap?</p>
<p><a href="https://i.sstatic.net/GCWFf.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/GCWFf.jpg" alt="Kola Superdeep Borehole BBC" /></a></p>
<p><strong>above:</strong> The borehole still exists - but the entrance has been welded shut (Credit: Rakot13/CC BY-SA 3.0), <strong>below:</strong> The borehole is located in the wilds of Russia's northern Kola Peninsula (Credit: Getty Images)</p>
<p><a href="https://i.sstatic.net/UgKbp.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/UgKbp.jpg" alt="Kola Superdeep Borehole BBC" /></a></p>
<hr />
<p><a href="https://www.youtube.com/watch?v=Qu6KyDUKViY" rel="nofollow noreferrer">https://www.youtube.com/watch?v=Qu6KyDUKViY</a></p>

CC BY-SA 4.0
2019-05-06T13:57:42.007Z
I'm not sure what they've lined it with, but it's entirely likely that the bottom stretch of the hole has closed up due to plastic deformation.
Spencer
CC BY-SA 4.0
2019-05-06T16:26:07.467Z
It is difficult enough to keep an operating well open; that is why "high collapse" strength casing is often used.
blacksmith37
CC BY-SA 4.0
2019-05-06T16:28:42.013Z
A well this deep would have well over 5 strings of concentric casing. The outer one would be about 3 ft diameter
blacksmith37
CC BY-SA 4.0
2019-05-07T12:46:29.060Z
@blacksmith37 And the bottom?
Spencer
CC BY-SA 4.0
2019-05-08T18:24:34.307Z
One could only guess; 0, 1, or 1 plus drill pipe; depending what was going on when they abandoned the hole. O = open hole with no casing yet run on the bottom . 1 = waiting for the next action , like cement to harden.  And for a well that deep there would be "tieback" casings and others I don't understand.
blacksmith37
CC BY-SA 4.0
2020-03-25T15:18:08.643Z
If the Russians followed normal safe practice for abandonment  ;They would have set a plug and pumped several hundred feet + of cement . It would be very risky to rely on a bolted or welded flange to seal a very deep well.
blacksmith37
<geology><crust><drilling>
If the Kola Superdeep Borehole were opened today, what would come out of it?
uhoh
# If the Kola Superdeep Borehole were opened today, what would come out of it?

(Asked by: username_0 on 2019-05-06)

The BBC News article [The Deepest Hole we have Ever dug](http://www.bbc.com/future/story/20190503-the-deepest-hole-we-have-ever-dug) says:

> This is the Kola Superdeep Borehole, the deepest man made hole on Earth and deepest artificial point on Earth. The 40,230ft-deep (12.2km) construction is so deep that locals swear you can hear the screams of souls tortured in hell. It took the Soviets almost 20 years to drill this far, but the drill bit was still only about one-third of the way through the crust to the Earth’s mantle when the project came grinding to a halt in the chaos of post-Soviet Russia.

The first image below shows the top of the Kola Superdeep Borehole, and the caption says that it is welded shut.

Is there any way to form a reasonable hypothesis what would happen if it were opened today? Would the 12 km deep well have filled with water, or helium, or natural gas, or is it likely to be filled with air? Would it be under tremendous pressure on the other side of the bolted-down cap?

[![Kola Superdeep Borehole BBC](https://i.sstatic.net/GCWFf.jpg)](https://i.sstatic.net/GCWFf.jpg)

**above:** The borehole still exists - but the entrance has been welded shut (Credit: Rakot13/CC BY-SA 3.0), **below:** The borehole is located in the wilds of Russia's northern Kola Peninsula (Credit: Getty Images)

[![Kola Superdeep Borehole BBC](https://i.sstatic.net/UgKbp.jpg)](https://i.sstatic.net/UgKbp.jpg)

---

<https://www.youtube.com/watch?v=Qu6KyDUKViY>

**Tags:** geology, crust, drilling

> **Comments:**
> **username_1**: I'm not sure what they've lined it with, but it's entirely likely that the bottom stretch of the hole has closed up due to plastic deformation.  
> **username_2**: It is difficult enough to keep an operating well open; that is why "high collapse" strength casing is often used.  
> **username_2**: A well this deep would have well over 5 strings of concentric casing. The outer one would be about 3 ft diameter  
> **username_1**: @username_2 And the bottom?  
> **username_2**: One could only guess; 0, 1, or 1 plus drill pipe; depending what was going on when they abandoned the hole. O = open hole with no casing yet run on the bottom . 1 = waiting for the next action , like cement to harden.  And for a well that deep there would be "tieback" casings and others I don't understand.  
> **username_2**: If the Russians followed normal safe practice for abandonment  ;They would have set a plug and pumped several hundred feet + of cement . It would be very risky to rely on a bolted or welded flange to seal a very deep well.  

---

## 3 answers

### Answer by username_3 on 2019-05-06. Score: 1 | Accepted answer

The only reasonable hypothesis is that it is filled with whatever it was filled with when the well was sealed.

A 12km long pipe with a sealed end is not going to have its contents replaced with something else easily. You could theorise that an intrusion of gas at the bottom opening of the pipe could expel liquid by replacement - possible, but slow.

> **Comments:**
> **username_0**: I was hoping for something like giant ants from the center of the Earth, or red-hot magma.  
> **username_3**: Heh - I'm with you on this - I always dreamt it would be like opening a plug, and lava emptying from the bowels of the earth.  

---

### Answer by username_4 on 2021-09-03. Score: 2

During the drilling, the hole was filled with "drilling mud", which served to lubricate the bit, carry the cuttings to the surface and power the bit via a turbine.

> When the well reaches a highest depth, there is a significant difference between the hydrostatic pressure of the mud column and the lithostatic pressure due to the weight of the rocks. As a result, the walls of
> the well can be destroyed (bend in), which leads to serious complications during drilling. In order to balance the rock pressure, there is an increase of density of the drilling mud to about 2 g per centimeter cubic.

[Application of Superdeep Drilling Technology for Study of the Earth Crust, O V Savenok et al 2020](https://iopscience.iop.org/article/10.1088/1755-1315/459/5/052066/pdf)

I expect they would not have gone to the expense of pumping out the mud (if even possible) as it would result in the hole caving in.

> **Comments:**
> **username_2**: The hole very likely collapsed whether not not there was mud in it . Collapse resistance depends on the collapse strength of the casing.  
> **username_5**: You have to pump out the mud, and all the cuttings resulting from the borehole drilling, otherwise your bit will get stuck. Plus, it was a scientific borehole, so the goal was to perform some study at depth. In fact, mud and resulting cuttings were brought to the surface (see page 5 of this report https://iopscience.iop.org/article/10.1088/1755-1315/459/5/052066/pdf )  
> **username_4**: @username_5  The mud and cuttings were brought up to the surface by pumping more (filtered) mud down the drill pipe. They would not be able to pump all the mud out of the hole (if that is what you are saying) with the equipment described.  
> **username_5**: You are right, in principle the mud at the bottom of the borehole would have a pressure of max ~240MPa (2g/cm3, times g times 12 km) ... unlikely to flush it out with N2 (or other gas) injection.  

---

### Answer by username_6 on 2020-03-25. Score: 2

Water has likely seeped in to the point of filling the hole up to sea level along with a high concentration of mineral deposits as a suspension of solids with the [180° Celsius bottom](https://www.atlasobscura.com/places/kola-superdeep-borehole?mc_cid=69025636df&mc_eid=34be11d5e3) creating a lava lamp like movement of those solids as they cool near the surface. Also assuming they left the drill and shafts inside, a whole lot of rusting metal.

> **Comments:**
> **username_0**: Welcome to Stack Exchange and thanks for your answer! I don't doubt that something like this is correct. In Stack Exchange it's important to include supporting links or sources for at least some aspects of answers (even though [this answer](https://earthscience.stackexchange.com/a/16882/6031) didn't). Is it possible to add for example something about how you arrived at the 180° C figure? Thanks!  
> **username_2**: Not so much rust as there is no continuous source for oxygen. they would not have left the drill string ( unless a big problem) . But the casing strings will be roughly one inch thick (25 mm) thick. Drill strings are normally leased and returned.  

---

