Drilling into active magma

I'd like to know what really happens. Presumably the drill bit can handle the temperature, as presumably the temperature gardient is small enough that several meters before it was nearly as hot? If the stuff is viscous, and not under much pressure, I'd presume not too much. But, can you withdraw the drill bit intact? Or does it get too gummed up? Could you avoid hitting magma, by monitoring drillhole temperature, and stopping when it gets too high? If the magma was under pressure, is the combination of viscosity, and thermal conductivity high enough it would only squeeze up a little way, than harden -or could the result be more dramatic?

When drilling geothermal wells we need to pump cold drilling fluids down the borehole to keep the equipment functioning. The bottom hole temperatures while we're drilling, even into magma, is only about 30 degrees C. We can't tell how hot it is down there in the formation while drilling, and in fact formation temperatures can only be determined some months later after the well is equilibrated. But we've had a lot of trouble drilling this well, and there was certainly evidence that well was hot before we started getting explosions down-hole and recovering cuttings of quenched glass and crystal mush. The drill bit came up completely intact after being stuck for some hours, and when it was recovered, it had no glass attached to it, looked to be in good condition, and had only minor blackening on the outside of the bottom hole assembly.

@bigTom: No, the drill bit cannot withstand the temperature; when it gets too hot the physical properties change and the bit fails.

"Drill fluid" is continuously pumped as the drill operates - this serves to wash out the stuff being ground away and also keep the drill bit cool.

I don't know what sensors can be put into the drills (if any); you'd have to ask someone from the oil and gas industry. Personally I would have expected the drill fluid to increase in temperature rather dramatically as the magma was approached, but I'm only guessing.

At 5km depth, the magma will be under very high pressure - perhaps 30-40MPa. The stuff is rather viscuous though and I wouldn't even expect it to make it out of the drill hole; it will cool down and plug itself. These holes really aren't that large - for oil and gas we're looking at typical sizes of 10-15cm diameter and occasionally a bit larger than that.

I like the story about drilling which is alleged to have triggered a "mud eruption" in Indonesia. :) About a year ago at a conference, a number of groups got together and said that drilling caused the eruption; the company that was drilling vehemently denies it of course since that would make them liable for the damage caused. I find it rather amazing that mud is being pumped out; I can imagine water being pushed out under pressure as with an artesian well, but mud is really something. Perhaps there is an aquifer with extensive horizontal silty layers which have not cemented into rock and that's the stuff being washed out.

Rhyolite magmas in Iceland? I thought Iceland was basaltic? Where do you get silicic magma in a spreading zone? Just curious...

Cheers,

N.

PS. Great blog BTW

Yes, there are temperature indicators you can put on the bit to determine temperature, but not until you've pulled the bit out of the well, nothing real-time. Also there are logging tools that are lowered down the well after the drill assembly is pulled out of the hole, but these are recording temps while cooling fluids are being pumped down-hole at a fairly high rate.
Also, there's plenty of rhyolite and granophyre in Iceland:) Obviously there's a lot more basalt though.

Re 4:
Extensive fractional crystallisation. MORB is generally tholeiite, and thus qtz normative, so fractionate enough mafics out and you get a silicic magma.

You can find (small) felsic residual layers in many large basaltic provences. For example:
http://lablemminglounge.blogspot.com/2009/01/non-basaltic-rocks-seen-in…

I am wondering if there have been any attempts to generate a
controlled flow of lava through a borehole for energy generation.
The pipes would need some sort of thermal insulation and/or pre-
heating to avoid solidification when the lava first flows through the relatively cool bore-hole, but presumably that can be achieved.
When the lava is sufficiently low in viscosity, one could
maintain a steady flow, which keeps the surroundings of the
bore-hole hot and prevents the lava from clogging to the walls.
I realize that its easier to extract energy from steam
than from sticky lava, but the large availability of lava near
the surface in some locations combined with the high energy release when solidifying could give it some potential. Any thoughts?.

In light of the discoveries of mega-volcanoes such as Yellowstone which is overdue to erupt, and Toba maybe it would be possible in the far future to create a controlled magma release preventing eruptions. Perhaps the Iceland experiments would be the forerunner of such controlled releases.

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