This is a brave effort, butreaching through five miles of rock is presently almost normal drilling practice,or at least the first four miles certainly is. Certainly a lot of important science will be determined and if theeffort is duplicated in the
Atlantic andseveral other locations, we may have surety in our knowledge of the oceaniccrust.
The temperature handled is thereal limit here, but 600 F is a long way form the information I would like tosee.
I wonder if it may be possible topush a graphite head bit through able to handle the heat behind a hydraulicpressure head. Fluid recovery maysuffice to characterize the material been passed through. How about titanium with a graphenelayer? My point is that we have not runout of tricks and it is worth the effort from a scientific and engineeringperspective.
The interesting question is howfar down on the sea bed we can really drill. We may be about to find out.
Scientists plan to drill all the way down to the Earth's mantle
March 25, 2011 byBob Yirka
Credit: World Book illustration by Raymond Perlman and StevenBrayfield, Artisan-Chicago
(PhysOrg.com) -- In what can only be described as a mammothundertaking, scientists, led by British co-chiefs, Dr Damon Teagle of theNational Oceanography Centre in Southampton, England and Dr Benoit Ildefonsefrom Montpellier University in France, have announced jointly in an articlein Nature that they intend to drill a hole through the Earth’s crustand into the mantle; a feat never before accomplished, much less seriouslyattempted.
The Earth’smantle is the part of the planet that lies between the crust and the iron ballat its center, and to reach it, would require drilling down from a position inthe ocean, because the crust is much thinner there. Even still, it would meandrilling through five miles of solid rock. And if that doesn’t sound hardenough, temperatures increase the farther down you go, and could reach as highas 570 degrees Fahrenheit; high enough to render useless most modern drillbits. Last but not least is the problem of atmospheric pressure, whichincreases the deeper you go, to somewhere in the neighborhood of 4 millionpounds per square foot near the mantle. That last one may not seem like much ofa problem, but with exploratory drilling, it becomes a problem rather quicklywhen you remember that it’s not just a hole they plan to dig, but a hole thatcan be used to extract samples from very far below.
To retrieve a sample, the drillers would have to rely on drills withouta riser (drills that use double pipes for venting gases) which would meanpumping seawater down into the hole through the drill pipe with sufficientpressure to force whatever is being dug back up to the surface so that it canbe examined.
This would not be the first time that a sample of the mantle would be recoveredhowever, as volcanoes and such have been forcing under-crust material to thesurface for eons; it would be the first time that a sample was found thoughthat hasn’t been tainted by the process that brought it up to us, and thatscientists say, is worth whatever the cost might add up to over time as theproject carries on through years of laborious drilling.
The pair plan to begin searching for a suitable site somewhere in thePacific this spring, but don’t expect the technology, nor the funding to allowthem to start drilling tillperhaps 2018.
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