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Drilling cost effectiveness and feasibility of high-temperature drilling - Reykjavik, Iceland, Workshop4
Drilling cost effectiveness and feasibility of high-temperature drilling - Reykjavik, Iceland, Workshop4
1-5 July 2007 ISOR
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Spallation Drilling for Deep Heat Mining
By 2050 at least 100 GW of electricity could be generated by geothermal power 
plants in the U.S. for a maximum investment of 1 billion US Dollars in research 
and development[1]. These numbers show clearly the enormous potential of 
geothermal power. However, temperatures high enough in terms of electricity 
production are commonly only found in holes reaching down to 4-10 km below 
the earth’s surface. The MIT report[1] shows that drilling costs increase 
exponentially with depth. New drilling technologies are therefore needed to 
reduce costs for geothermal wells. Apart from conventional mechanical drilling 
by means of a rotary drilling bit, there is a technology called “Spallation Drilling”. 
Therein, a flame jet or laser is directed to the rock to cause fragmentation. In 
simple terms, spalling is a form of crackling caused by an unequal expansion of 
rock crystals. While this technology, also known as “thermal rock 
fragmentation”, is already used in Russia and the Ukraine to drill large diameter 
holes in surface mining, in our laboratory we aim to investigate the possibility of 
using this technology to drill deep holes for geothermal power plants. Beyond 
3000 meters supercritical conditions for water are found. Our theoretical and 
experimental experience with hydrothermal flames is used and shall allow 
spallation in this supercritical environment. Fundamental experimental and 
theoretical research will been done on heat transfer, transport of spalled 
material and burner nozzle design. Ignition and stability of the flame are further 
investigated, as these are main conditions for the operation downhole. These 
data then allow the design of a pilot facility for geothermal application.

[1]	The Future of Geothermal Energy, MIT press, Cambridge (2006),
Id: 6
Place: ISOR
Grensasvegur 9
Room: Vidgelmir
Starting date:
02-Jul-2007   15:40
Duration: 20'
Primary Authors: Mr. ROTHENFLUH, Tobias (ETH Zürich)
Prof. RUDOLF VON ROHR, Philipp (ETH Zürich)
Presenters: Mr. ROTHENFLUH, Tobias
Material: slides Slides

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