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Rising to the challenges of geothermal drilling

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Rising to the challenges of geothermal drilling
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There are already around 130 geothermal power facilities operating in Europe, but that number could double in less than a decade.

There is therefore a need to ensure they are safer, more reliable, increasingly cost‐efficient ‐ and environmentally friendly.

To this end, European scientists have been designing and developing new technologies that are currently being tested in Iceland.

What are the main risks in geothermal drills?

International expert Ingólfur Örn Þorbjörnsson, Innovation Manager at the Isor Iceland GeoSurvey Institute in Reykjavik, explains what happens deep down at 2,000 metres, where the steel casing comes up against underground heat of enormous temperature at high presssure:

"Normally when you have geothermal energy in the wells going down to get geothermal steam coming out from the earth, you have high temperatures and the steel is elongated, cemented in and expanding.

"So expansion is not possible and that is why you have problems with the casings, or the steel in the pipes.

"And when you actually have the thermal expansion and you have constrained the steel, it collapses, almost closing the well, or half-closing it.

"Or when you cool it down, it will tear apart the pipe from the couplings.

"The pressure is way above the yield stress of the material up to the fractious stresses of the material. So it is way above what we normally accept".

"And actually what we have seen in normal 250ºC to 350ºC temperature wells, having analysed 230 of them, is that 136 of them were what we call "production wells".

"75 of them had reported incidents, meaning that they had some kind of incident in them; it could be a total failure, or a minor failure. But it was not perfect as it was intended to be".

"The flexible couplings that we are introducing are actually to cope with these stresses, causing these problems. So taking away these stresses will hopefully take away these problems or minimise them".