Drilling Into The Earth

[Deepwater6]

http://www.cnn.com/2012/10/01/tech/mantle-earth-drill-mission/index.html?hpt=hp_t3

 

This CNN article tells of a $1 billion mission to reach the Earths mantle. Unless I missed it they did not say what kind of drill bits they would use.

 

I would think the bits would change with different elevations depending on what they are trying to penetrate to speed the process? Or do they always use the same kind not knowing when they will need the strongest bit? Diamond tipped the most durable or is there something stronger?

 

How deep could we feasible go?

Edited October 2, 2012 by Deepwater6

[belovelife]

i know there is a bit harder than diamond, but using fracking and other processes make the drilling easier,

 

i was communicating with chevron before the global climate change confrence in africa

 

they asked what i would say if i went

 

i told them, if i were chevron, i would say, since we have the most advanced drilling procedures in the world

we are going to usher in a new era of geothermal power production

 

a few months later, they sent me a layer in google maps that defined the amount of energy was availible in the us based

on depth and heat

 

pretty cool layer for my google maps :)

[Guest MacPhee]

http://www.cnn.com/2012/10/01/tech/mantle-earth-drill-mission/index.html?hpt=hp_t3

 

This CNN article tells of a $1 billion mission to reach the Earths mantle. Unless I missed it they did not say what kind of drill bits they would use.

 

I would think the bits would change with different elevations depending on what they are trying to penetrate to speed the process? Or do they always use the same kind not knowing when they will need the strongest bit? Diamond tipped the most durable or is there something stronger?

 

How deep could we feasible go?

 

Using "drill bits" seems a rather old-fashioned way to penetrate the Earth's depths. It sounds like a 19th-Century Jules Verne novel - Yankee engineers build a giant 1,000ft long steam-powered drill! Such crude low-tech methods need not concern us today. If we really want to penetrate the Earth's crust, we could use a nuclear bomb.

 

A bomb of really high-yield, say 20+ megatons. This could be sunk down to the ocean-floor. Such as the floor of the Mariana Trench, which is some 7 miles deep. At that depth, the massive nuclear detonation would cause little harm up on the surface.

 

But the explosion would punch a big hole in the ocean-floor. The hole might breach the crust. If it didn't, we could just send a second bomb down, to explode at the bottom of the first bomb's crater. Then another bomb if necessary. Eventually, we'd blast our way through into the mantle.

 

Then we'd see what happened. Wouldn't it be exciting!

Edited October 3, 2012 by MacPhee

[Turtle]

http://www.cnn.com/2012/10/01/tech/mantle-earth-drill-mission/index.html?hpt=hp_t3

 

This CNN article tells of a $1 billion mission to reach the Earths mantle. Unless I missed it they did not say what kind of drill bits they would use.

 

I would think the bits would change with different elevations depending on what they are trying to penetrate to speed the process? Or do they always use the same kind not knowing when they will need the strongest bit? Diamond tipped the most durable or is there something stronger?

 

How deep could we feasible go?

 

i think this is a worthy project, especially because in many ways we know more about what's outside our earth than in it.

 

to the best of my knowledge we can in theory go into the mantle until the temperature is high enough to melt the bit. reading your article they mention techniques being used for oil and gas extraction, however drilling for mineral exploration uses some different techniques that seem better suited to this project. here's a snippet on such a technique; the entire article fills is the whole field. ;) if i recall correctly, RAB is the technique they used to rescue those miners in Chile.

 

the greatest challenge in this effort is not the bit, it's threading that bit in a ~1 foot hole at the bottom of the ocean. this has to be done everytime the bit breaks or wears out.

 

drilling rigs

...

Percussion rotary air blast drilling (RAB)

 

RAB drilling is used most frequently in the mineral exploration industry. (This tool is also known as a Down-the-hole drill.) The drill uses a pneumatic reciprocating piston-driven "hammer" to energetically drive a heavy drill bit into the rock. The drill bit is hollow, solid steel and has ~20 mm thick tungsten rods protruding from the steel matrix as "buttons". The tungsten buttons are the cutting face of the bit.

 

The cuttings are blown up the outside of the rods and collected at surface. Air or a combination of air and foam lift the cuttings.

 

RAB drilling is used primarily for mineral exploration, water bore drilling and blast-hole drilling in mines, as well as for other applications such as engineering, etc. RAB produces lower quality samples because the cuttings are blown up the outside of the rods and can be contaminated from contact with other rocks. RAB drilling at extreme depth, if it encounters water, may rapidly clog the outside of the hole with debris, precluding removal of drill cuttings from the hole. This can be counteracted, however, with the use of "stabilisers" also known as "reamers", which are large cylindrical pieces of steel attached to the drill string, and made to perfectly fit the size of the hole being drilled. These have sets of rollers on the side, usually with tungsten buttons, that constantly break down cuttings being pushed upwards.

 

The use of high-powered air compressors, which push 900-1150 cfm of air at 300-350 psi down the hole also ensures drilling of a deeper hole up to ~1250 m due to higher air pressure which pushes all rock cuttings and any water to the surface. This, of course, is all dependent on the density and weight of

...

[CraigD]

http://www.cnn.com/2012/10/01/tech/mantle-earth-drill-mission/index.html?hpt=hp_t3

 

This CNN article tells of a $1 billion mission to reach the Earths mantle. Unless I missed it they did not say what kind of drill bits they would use.

The CNN article doesn’t. This NPR interview transcript does:

"Dr. TEAGLE: The kind of drill bits are it's a little bit - actually adapted industry bits, and they are generally made of hardened steel with, sort of, roller cones of tungsten carbide. Ideally, when drilling hard rock, you'd want to have some and if you were doing this on land, you would have your drill bits impregnated with diamonds."

I would think the bits would change with different elevations depending on what they are trying to penetrate to speed the process? Or do they always use the same kind not knowing when they will need the strongest bit? Diamond tipped the most durable or is there something stronger?

I get the impression that the sort of drill bits used are made to be as hard and durable as possible, not finely customized for the material through which they’re drilling.

 

Though I’m only casually acquainted with drilling technology, the impression I get is that the actual drill heads and shafts haven’t changed dramatically since the last major attempt to drill through the thin ocean crust to reach the mantle, 1961’s Project Mohole.

 

The failure of Project Mohole wasn’t due to technical failures, but administrative ones: the planned transfer of project control from the informal group of scientist who started it and completed its first phase, the drilling of several small (less than 200 m) holes in about 3600 m deep water to the NSF was troubled, then the projects US government funding was eliminated.

 

The improvements that should result in the success of the planned drilling through to the mantle by the drilling ship Chikyū are in large parts administrative: rather than relying on a single government or agency, the project is managed by an program involving scientist, institutions and agencies from many nations, making it less likely that political misfortunes in any one country could (pardon the pun) sink it.

 

The major technical improvements since the 1960s, as best I can tell, are in the ships’ postion-holding ability, which is greatly improved by computer control systems and GPS.

 

How deep could we feasible go?

From the NPR interview, I gather that the project plans to go only a few hundreds meters deeper than the crust (which is about 7000 m thick) – not necessarily because it couldn’t go deeper, but because it’s more scientifically valuable to sample the mantle horizontally than vertically.

 

Using "drill bits" seems a rather old-fashioned way to penetrate the Earth's depths.

It is fairly old fashion. It also works. Conventional drilling bits, shafts, and the rest have been used, in dry-land installations, to drilled deeper than 12000 m.

 

As I mentioned above, had it not been killed by administrative and political mishaps and misfortunes, Project Mohole would likely have successfully reached the mantle in the 1960s, using conventional drilling technology.

 

If we really want to penetrate the Earth's crust, we could use a nuclear bomb. A bomb of really high-yield, say 20+ megatons. This could be sunk down to the ocean-floor.

...

But the explosion would punch a big hole in the ocean-floor. ...

This is an interesting idea, and has precedents in the US’s Operation Plowshare and the USSR’s Nuclear Explosions for the National Economy.

 

There’s a fundamental physical problem, however, with attempting drill a 7000 m long, less than 1 m diameter shaft using explosives, nuclear or otherwise: explosives are useful for excavating large volumes of material, producing a roughly conical crater. They aren’t for boring long, thin shafts.

 

A bomb exploded on the surface of the ocean floor will not “punch through” it, but expend most of its energy moving the water above it. In order to make a substantial “dent” in the sea floor, it is necessary to bore a hole in it, place the explosive at the bottom of the hole, and explode it, producing a crater slightly less deep than the bore hole.

 

Although this has never been tested underwater, it has on land. The largest such test was the 1962 Sedan test. Using a 104 kt fission/fusion bomb exploded in a 193 m deep hole, it produced a roughly 100 m deep, 390 m diameter crater, removing about 5,000,000 m³ of material.

 

At that depth, the massive nuclear detonation would cause little harm up on the surface.

I agree. This was demonstrated by 1955’s Operation Wigwam, which exploded a 30 kt fission bomb 660 m underwater (about 4600 m above the ocean floor). Although this produced a 270 m high spray dome, almost no radiation was detected in its aftermath.

 

Boring a hole in the ocean floor with nuclear explosives is an interesting idea, but for it to be done, you’d need to do more than just exploding nuclear bombs on it. You must designed a means to contain the explosion, forcing it in a narrow path – a ““nuclear shaped charge”. Though some research into this has been done, I think serious, well-funded research ended in 1963, due to the Limited Test Ban Treaty.

[Eclogite]

I get the impression that the sort of drill bits used are made to be as hard and durable as possible, not finely customized for the material through which they’re drilling.

This would be incorrect. In drill bit design we focus, largely, on four key performance indices: rate of pentration durability, stability and steerability. Since increasingly drilling is done with bits fitted with many polycrystaline diamond cutters, the bit can be 'tuned' to deliver the required balance of these indices for a particular lithology and application. This is done by varying the number and size of cutter, the specific type of cutter manufacturing process, the profile of the bit, the orientation and exposure of the cutters, use of secondary cutting elements, geometry of gauge pads, body material, hydraulic arrangements etc.

 

In some instances we manufacture a specific bit with precise characteristics for a single application, though it is more likely to fit a generic, though closely constrained application.

 

Though I’m only casually acquainted with drilling technology, the impression I get is that the actual drill heads and shafts haven’t changed dramatically since the last major attempt to drill through the thin ocean crust to reach the mantle, 1961’s Project Mohole.

While superficially this is true - we have a long string of pipe turning to the right with a bit with cutting elements on the end - the details have advanced dramatically. If I use a single example to illustrate. Using current technology the 12 1/4" hole section in a typical Central North Sea well may be drilled with one bit. If we go back thirty years, not fifty, we find that same section required twenty to twenty five bits to drill. Progress is, if anything, accelerating.

[belovelife]

does anyone know the mix to create bits harder than diamond?

[Eclogite]

does anyone know the mix to create bits harder than diamond?

The issue with such a bit is that there is typically a trade off between abrasion resistance and impact resistance. Any artificially constructed material harder than diamond would likely be more brittle than diamond. Many of the advances in the performance of PDC bits (Polycrystaline diamond compacts) have revolved around addressing this trade off. There is still a considerable way to go along current development lines: seeking to use the harder material does not look like an economically viable approach at this time.

[sunshaker]

I do not think it will be how hard we can make the drill bits, it will mostly be done through some kind of "vibration drilling", everything as a frequency, we can break anything down once we have the right frequency.

Resonant shattering of neutron star crusts

http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.108.011102 vibration

Edited October 9, 2012 by sunshaker

[Lancewen]

Deepest Hole Ever Drilled (temperature seems to be a big problem)

 

 

 

The deepest hole ever drilled is the Kola Superdeep Borehole, on the Kola peninsula in the northwest corner of Russia, located near Finland. It was drilled for scientific research by the USSR. Like many large research boreholes, it had a number of offshoots from the central branch, and the deepest, SG-3, was 12,262 meters (7.6 miles) deep. The borehole reached this depth in 1981. The temperature at this depth was 180°C (356°F), at which point the rock became more like a plastic than a solid, stopping further drilling.

 

Even though the borehole in question was 7.6 miles deep, it only penetrated a third of the Baltic continental crust. The rock at the bottom of the hole was about 2.7 billion years old, and samples brought from near the bottom contributed invaluably to the study of geology and geophysics at the time. The original depth goal was 15,000 meters (9.32 miles), but a faster-than-expected increase in temperature forced a premature halt to the project. If the borehole had extended down to 15 km, the projected temperature would have been 300°C (572°F), well over the maximum operating temperature of the drill bit.

 

 

 

http://www.wisegeek.com/what-is-the-deepest-hole-ever-drilled.htm

[Eclogite]

I do not think it will be how hard we can make the drill bits, it will mostly be done through some kind of "vibration drilling", everything as a frequency, we can break anything down once we have the right frequency.

Numerous alternative methods of drilling have been theorised upon, tested in the lab and in the field. Thus far, after over a century, rotary drilling with drill bits reamins the only effective method. Will this change? Probably, but there is nothing on the horizon to suggest it will be soon.

[Deepwater6]

Eclogite you seem to have some experience with this subject. Getting back to drilling in the ocean, wouldn't it be a problem with cool ocean water coming in contact with the higher temps going this deep or deeper?

 

Also just happen to catch a show on the Science channel tonight (Journey to the center of the Earth). It mentioned extreme pressure as a limiting factor as well.

[belovelife]

there seems to be a need to develop some sort of liquid cooling system for the bit,

 

looking at a glass torch, this should not be that difficult

[Eclogite]

Eclogite you seem to have some experience with this subject. Getting back to drilling in the ocean, wouldn't it be a problem with cool ocean water coming in contact with the higher temps going this deep or deeper?

 

Also just happen to catch a show on the Science channel tonight (Journey to the center of the Earth). It mentioned extreme pressure as a limiting factor as well.

You rightly highlight the issue of temperature. The contact with ocean water would, of course, be indirect and not in itself a problem. Drilling muds are continuously recirculated so that the the mud at the surface has time to cool before being circulated back down the drill string. On the way down it is warmed up by the mud passing up the borehole annulus, which is of course simultaneously cooled.

 

The difficulty is that the ambient bottomhole temperature gets to a level that either limits or prohibits the use of many drilling devices. Electronic measuring instruments cease to fucntion; roller cone bits with internal bearings fail as the lubricant is heated; fritctional temperature of PDC cutters against the rock added to ambient temperture lead to thermal degradation of the cutters; downhole drive systems fail because of elastomer content; etc.

 

There are various solutions in use that allow the industry some success - at great expense - of drilling in high temperatures, but none as high as would need to met for this kind of project. I am not saying it is impossible, just that a radical new approach would be required.

[sunshaker]

Intersting videos on sonic drilling, still early days but as potential.

[CraigD]

does anyone know the mix to create bits harder than diamond?

As best I’ve been able to learn from this thread and wider online research, there isn’t currently any material harder than diamond (it’s necessary to be precise here, and say cubic structured diamond) suitable for use in drill bits, though some material scientists are working on changing this.

 

From my reading, the leading candidate materials are 2 synthetic materials,

wurtzite boron nitride (not to be confused with the mineral wurtzite, a kind of zinc ore), which has been shown in computer simulation to be 18% harder than cubic diamond, and hexagonal diamond (also called lonsdaleite), show in sims to be 58% harder. WBN might be the winner between the two, because it’s more chemically stable.

 

According to this 2009 NewScientist article, as of then, there was no good physical testing of either material, because very little of either had been synthesized. Whether the cost of finding and using industrial methods of making enough of such materials for drill bits and other tools are worth their superior hardness seems to me anybody’s guess.

 

Whatever the diamond-or-better hardness material, I think tools made of it will resemble present day one. I found this picture from this 2005 industry journal article

of a PDC drill bit, helpful (and the text of the article, too). Notice the difference between this “scraper” type bit, and this “crusher” type one:

Then note that the kind of bit Damon Teagle is talking about using to drill through the Earth’s crust to its mantle is yet another kind, a core-sampling type bit. Unlike, for example, commercial oil-drillers, whos main goal is to reach and extract oil, geologists like Teagle are interested in learning as much as possible about the structure and composition of what their drilling through, making a less efficient drill bit design their preferred choice.

[Deepwater6]

There is a show on the H2 - History channel (2) called, "Journey to the Earth's Core." Tonight starting at 8pm.