Activists who are against natural gas in the United States have invented a variety of problems; flaming tap water, earthquakes, headaches, even that it will cause the earth to deflate.
Good thing they don't live in Norway, where energy extraction by the Nextdrill research project is going thousands of meters into the ground, in order to exploit another of nature's bounties: tinkering with the Earth’s molten core and radioactive isotopes in the Earth’s crust. The project is drilling down to where temperatures are so high it can be used for district heating and electricity generation.
As in all drilling operations, they need to rush in order to keep costs at a minimum. If geothermal heat is to be competitive as a source of energy, they need to be able to drill at high speed - and they don't want loss of time, like having to bring the drill-bit to the surface for replacement.
Three members of the Nextdrill project – SINTEF, the Swedish company Sandvik and Germany’s H.C. Starck – are collaborating on the development of materials for a drill-bit with a long working life. Another participant is the Norwegian technology company Resonator, which is in the process of developing an electric percussion rotary drill, a tool that crushes rock by dealing it hammer-like blows as the drill-bit turns. Electrical operation offers the possibility of remote control and more energy-efficient drilling systems than technology based on today’s pneumatic or hydraulic systems.
Like with fracking, two types of well need to be drilled to exploit this energy; one to pump cold water down, and the other to bring hot water up again. The drill-bit that does this job must be able to crush hard rock types such as granite. The main aim of the Nextdrill project is to identify a combination of hard-wearing, durable materials and technical solutions that can do this.
Right: In future drilling in hard rock that lacks natural cracks, as in Norway, drilling a series of radiating bore-holes between the wells is a possibility. An alternative method is to create such cracks by subjecting the bedrock to extremely high hydraulic pressure (so-called “fracking”). Illustration: SINTEF/Knut Gangåssæter.
The first test will be in August
In the course of this year the Nextdrill project will carry out its first small-scale drilling trials near Ås in Akershus County. In August and again in November, a specially designed version of Resonator’s percussion rotary drill will tackle hard rock. It will be fitted in turn with commercially available drill-bits and bits made of the highly wear-resistant materials that are being developed by the project.
The trials have two main purposes. They will provide new knowledge about how wear occurs on drill-bits when rock is crushed using an electric percussion rotary drill. The tests will also show how the number of impacts per unit time affects the speed of drilling.
“Although we will not be drilling very deep during these tests we do expect to gather important data for the next stages of our efforts to develop highly durable materials,” says Kane.
SINTEF’s project manager Alexandre Kane checks out a drill-bit that the Swedish company Sandvik has developed for mining operations. In future commercial drilling for deep geothermal energy, wells may need to be as much as a metre in diameter. Photo: SINTEF/Thor Nielsen
The drill-bit needs to be able to withstand a high level of friction, in addition to enormous amounts of mechanical abuse resulting from the high-frequency hammer impacts.
“Laboratory trials and virtual experiments performed by computer models have taught us a great deal about drilling through granite, and have enabled us to develop models that we use to find the optimal form and composition of the drill-bit. The drilling trials at Ås will give us measurements that will let us further improve the computer model,” says Kane.
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