[Bass]

Neil
Just for fun, I once visited the 9000 foot level of an operating mine.  I pity the miners that work at that depth- bad air, excessive heat, rock bursts, scalding water- but I had fun.  The ride down the hoist- basically free-fall in an open cage for 7000 feet, then 2000 feet to slow down and stop, was definitely one of the highlights.  They should probably advertise and charge folks for that ride!
Like I said, just for fun.

Subduction causes orogeny.

[another_someone]

quote:Originally posted by JimBob
I must agree with Bass. Not likely due to the high pressures which increase viscosity so much.

But if you punch a hole down to that depth, unless you maintain substantial pressure within the hole, is it not going to have the consequence of a pressure release?

George

[JimBob]

We already have these holes to the mantle. They are called mid-ocean ridges and there is no massive pressure release there.



The mind is like a parachute. It works best when open.  -- A. Einstein

[another_someone]

quote:Originally posted by JimBob
We already have these holes to the mantle. They are called mid-ocean ridges and there is no massive pressure release there.

Not comparable.  I am not saying they are irrelevant, only that it is not the same situation.

Mid oceanic ridges push the match up a 10 Km gap, before reaching cold air – that is 10Km of rock pushing back down against the flow of lava.

This is why I allowed the possibility that a bore hole down to the mantle might need positive pressure to hold back the lava.  Otherwise, rather that the lava having to push back against 10Km of basalt, it merely has to push back against 10Km of air.  A significant difference.

Beyond that, we really don't know at first hand what happens 10Km beneath the mid oceanic ridges; we see them only as they arrive at water level.  By comparison, if we drill down to meet the mantle, we would have to be concerned very much about what happens to the drill mechanism at 10Km (or 35 Km, depending on where the bore hole happens to be) beneath the surface, where the crust meets the mantle.

I never suggested that the mantle would gush to the surface, but the fact that the mantle is capable of providing enough pressure to push basalt 10Km up through the crust at mid oceanic ridges clearly indicates that the pressure available there must be comparable to the weight of 10Km of basalt rock.

George

[Bass]

George
Keep in mind that the basalt that erupts at the mid-oceanic ridge is not the same material that you would hit if you drilled down 10 km to the top of the mantle.  The basalt has differentiated- probably several times- before reaching the surface.  Seismic evidence suggests that even the upper mantle behaves like a high-viscosity plastic material (I always imagined a crystal mush).  
Pulling tectonic plates apart at the mid-oceanic plates creates lower pressure zones that allow the more liquid part (basalt) of the magma to ascend, leaving behind the more crystalline portion (peridotite).
Also, the mantle material would be pushing back against a 10km hydrostatic head, not merely air pressure.  The small diameter of any borehole would not release enough pressure to cause an eruption of mantle material.

Subduction causes orogeny.

[tanian]

I know this is a bit of a tngent, but I find the idea very interesting.

I was recently reading an article that compared the rotation of the earth and the earths orbit around the sun to a centrifuge.

If you fill a jar with nuts of different sizes, what you eventually get is the nuts seperating according to size- finer particles at the bottom and larger ones at the top. If you spin the jar on a centrifuge the process reverses- large at the bottome, small at the top. The argument goes that the Earth has formed the same way, that sand etc. wouild be the smaller particles and that therefore the denser particles are locked down underneath the earths surface. The argument goes thus- if we have discovered all the elements at this level, then there is no reason to say there arent other elements locked deep within the earth theat we have yet to discover.

Thr Rusians in the good old evil empire days have acchieved the deepest penetration into the earths crust. They used a 2 inch drill bit and spend millions of $ for several years to acchieve this before the project was finally scrapped. I have the figure 13 km in my head but find this ridiculously high. I'm assuming I am wrong but cannot locate the article at present, either way the earth is something far far higher than this in depth.

Anyway, what do you think are the chances of finding unique elemental materials at lower depths?

[another_someone]

quote:Originally posted by tanian
Anyway, what do you think are the chances of finding unique elemental materials at lower depths?

We may well find new minerals at great depth, but unlikely to be new elements.

Bear in mind that we have already synthesised elements up to atomic number 111 under laboratory conditions.  None of the transuranic elements have long term (stability plutonium has a half-life of 80 million years, and neptunium-237 of 2 million years, but other elements can have half-lives measured in milliseconds), and so unless they are being continually renewed (as might be the case in the nuclear furnace at the core or the Earth), then all that would remain (if it ever existed) is a very, very, small proportion of what was there at the time when the Earth was first formed.

George

[tanian]

Essentially ultra-rare items and/or absurdly high proportions of lead then?

[pignut]

On a slightly different tack, the earth is very big, very heavy, spinning and orbiting the sun at an extremely high speed....maybe we just need to attach the earth to a very big dynamo :-)

[another_someone]

quote:Originally posted by pignut

On a slightly different tack, the earth is very big, very heavy, spinning and orbiting the sun at an extremely high speed....maybe we just need to attach the earth to a very big dynamo :-)

It already is – that is what is generating the Earth's magnetic field.

George

[Matthewsb]

quote:Originally posted by neilep

Hello all,

What a wonderful day !!..

I know our ability to drill deep into the Earth is very very limited...but do you think as our progress continues to dig deeper, that the heat of the planet could be a source of energy ?

whajafink ?

Men are the same as women, just inside out !

[Matthewsb]

That is a good topic. We need more scientists to do R and D on the Energy inside the earth and how to tap into it.
Matthews Bantsijang

[JimBob]

See current discussion under "Geology/Paleontology" http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=4559



The mind is like a parachute. It works best when open.  -- A. Einstein

[Atomic-S]

quote:I was thinking either of some very aggressive cooling

If the well requires very aggressive cooling, then it may be ready to produce power already!  Which can be commenced while drilling continues for even more power.

quote:With non contact drilling the shaft will need be reinforced somehow unless the nature of the drilling will create a clean & secure surface, effectively creating a solid pipe from the very material you're drilling through.

Chilled lava might do the job.

quote:Maybe pump coolant down a channel, and into the space between the drill mechanism and the bore hole wall, and then use acoustics or magnetic fields to push the coolant away from the drill mechanism, thus simultaneously ensuring that hot coolant it kept away from the drill mechanism, and that the drill mechanism stays away from the bore hold walls.

If the coolant is being pumped in and out, (In through the pipe, and out around it) does this not take care of all difficulties?

quote:Another option would be to have two or three large wheels, or cylinders, around the drill mechanism. The wheels will be constantly rolling around the perimeter of the bore hole.

Like roller bearings.

quote: They would both smooth out, and compact the side of the bore hole, as well as ensuring the the drill mechanism itself is kept away from the sides of the bore hole.

Is this for thermal purposes or to reduce frictional wear?

quote: Because they are large diameter wheels, only a very small proportion of the rim is in contact with the wall at any one time, and since it is constantly rolling, that small part is never in contact for very long, and so will not absorb a great deal of heat. It will still be necessary to aggressively cool the wheels, but they need to actually have any part that will get that hot, so long as the heat can effectively be dissipated from those parts of the wheel that are not in contact with the wall, so they are cool enough once they come back in contact with the wall.

. I am not quite sure I understand this; in particular, just what coolant will be present, and how it will be circulated. It would seem to me that if coolant is pumped in through the drill pipe and out around it, this basically eliminates all questions of overheating; and that if the heat is so great that it does not, then these rolling cylinders will not be of much use in any case, because the temperature at any one depth will be nearly uniform at all radii from the axis of the pipe to the wall of the hole.

[realmswalker]

what about a laser based drill?
It could reduce the rock to gaseous particles that could then be sucked out the top.
it would also melt the walls so they would be stable.

[JimBob]

Laser drilling is in development. The drilling mud (fluid) is already the first or second most expensive cost of drilling, after total rig costs - crew and machine rental, a package deal. The drilling mud does four things, cool the bit and the drill string, lubricates the bit and, because of the high viscosity of the mud, brings the rock chips up. It also exerts a hydrostatic pressure on the porous rocks to keep the fluid in the rocks from coming to the surface

The typical drill bit is a 3-cone bit that turns and chips away rock as it turns. Drilling mud is pumped down the inside of the drill pipe, jetted out of the nozzels on the upper part of the bit and back up the outside of the drilling pipe (pictures on Wikipedia http://en.wikipedia.org/wiki/Drill_bit)

Drill pipe is made of steel and a substitue has yet to be found. The problem is that with all current technology, a huge amount of weight is needed to cause the bit to chip the rocks. Another material will not put the weight on the bit that steel does.




The mind is like a parachute. It works best when open.  -- A. Einstein

[Atomic-S]

So according to this, when drilling into hot material, the drill mud should cool it, rendering it solid and therefore drillable using conventional means?

[JimBob]

I very much doubt drilling mud would be capable of cooling much above 350 degrees F. The drilling fluid (even if oil-based) would vaporize very quickly, causing a gas bubble down-hole. This is a very bad thing. The rapidly expanding gas from the phase change causes the mud above it to be blown back up the hole and the well becomes unstable. People get killed on the surface when something like this happens. Not many peoole in their right mind would even consider continued drilling to be possible, much less safe.



The mind is like a parachute. It works best when open.  -- A. Einstein

[heikki]

[]

Hi.

We cannot make deep hole to center of earth by usin todays drilling-systems so that drilling-machine is surface and we use long drilling-rod and diamond or etc. drilling-head.

What we need?

Drilling machine which can go down the hole like canal-hole (england-france) drilling maker but directly vertical direction.
Also it need vertical lift to carried up  that drilled stuff and drilling equipments to maintenance for while( if machine is full automatic version).

Scientifical it is quite interesting and important project, but technical, is it possible? Also what happend if under drilling tunnel-hole is big pressure which comes out through tunnelhole?

Lift-tunnelhole-drilling-machine, vertical direction, full automatic.

How long it take to make deep hole (squaremeter 25m2 or something size to center of earth, hole distance 6500km=6500000meter?

Hmm. If machine can make 1m/24h then one year it goes 365m and ten year it goes 3650m = 3,65km. Diameter of earth ball is ab.13000km.
 
13000km/3,65km=3561year/2=1780year.

So, it speed is 1m/24h then year 3786 drilling head is center the earth.

Lift high is 6500km = 6 500 000m? Technics is problem because todays higher lift is probably few hundred meter.

Hmm. Unpossible work to do, i think.

 []

[Atomic-S]

quote:I very much doubt drilling mud would be capable of cooling much above 350 degrees F. The drilling fluid (even if oil-based) would vaporize very quickly, causing a gas bubble down-hole. This is a very bad thing. The rapidly expanding gas from the phase change causes the mud above it to be blown back up the hole and the well becomes unstable. People get killed on the surface when something like this happens. Not many peoole in their right mind would even consider continued drilling to be possible, much less safe.

Well, now let's see: if we have that kind of steam pressure available, it suggests the possibility of capturing it to drive a turbine. Now of course drilling mud may not be the ideal fluid for driving a turbine, but is there some way we could get around that problem? Would there be some way of circulating drilling mud in the lower portions of the hole, where resistance to pressure is most needed, but then, at a depth somewhat lower than that at which the water could vaporize, put it through some kind of a heat exchanger so as to transfer the heat to plain water for the rest of the trip up the hole. That circuit would be handled as a pressurized steam system, and connect into a turbine, so that geothermal energy would be harnessed even while drilling was in progress.