Science & Technology

Geothermal Energy: Seismic Activity From Drilling a 3,000 Meter Deep Well

That is the view of the Venelle-2 properly. The properly was designed to pattern supercritical fluids. Credit score: © Riccardo Minetto

Researchers from the College of Geneva have studied the seismic exercise recorded in the course of the drilling of a geothermal properly and proven that it didn’t spark any main earthquake.

Though stopping local weather change is difficult, it’s crucial to sluggish it down as quickly as attainable by decreasing greenhouse gasoline emissions. However how can we meet the rising power demand whereas decreasing our use of polluting fossil fuels? Geothermal power is an environment friendly, non-polluting resolution however in sure instances geothermal operations should be dealt with with care. Reaching probably the most highly effective sources of obtainable power means drilling deep into the layers of the earth’s crust to search out geothermal fluids with excessive power content material (sizzling water and gasoline launched by magma). But, the deeper we drill the higher are the subsurface unknowns controlling the soundness of the Earth’s crust. Destabilizing the precarious equilibrium at depth with geothermal wells could reactivate the geological layers inflicting earthquakes. Researchers on the College of Geneva (UNIGE), Switzerland, working in collaboration with the College of Florence and the Nationwide Analysis Council (CNR) in Italy, have studied the seismic exercise linked to geothermal drilling in the hunt for supercritical fluids. They found that the drilling didn’t trigger uncontrolled seismic exercise. This drilling beneath such vital circumstances means that the expertise is on the verge of mastering geothermal power, paving the best way for brand spanking new sources of non-polluting warmth and electrical energy. You’ll be able to within the Journal of Geophysical Analysis.

The scientific group agrees that CO2 emissions must drop by 45% by 2030 and that 70% of our power should be renewable by 2050. However how can these targets be met? Geothermal energy — a renewable type of power — is a part of the answer. Quite a lot of international locations, together with Switzerland, are already exploiting geothermal power to supply warmth from shallow wells. Till 1,500 meters such expertise usually presents little threat. “To generate electrical energy, nonetheless, we’ve to drill deeper, which is each a technological and a scientific problem,” factors out Matteo Lupi, a professor within the Division of Earth Sciences in UNIGE’s College of Science. In actual fact, drilling deeper than 1,500 meters requires particular care due to the unknown components regarding the subsurface improve. “Beneath these depths, the soundness of the drilling website is increasingly tough and poor selections may set off an earthquake.”

The Larderello geothermal subject in Tuscany — the world’s oldest — presently produces 10% of the world’s whole geothermal electrical energy provide. We all know that at about 3,000 meters depth, we attain a geological layer marked by a seismic reflector, the place it’s thought that supercritical fluids could also be discovered. Supercritical fluids yield an unlimited quantity of renewable power. The time period supercritical implies an undefined section state — neither fluids nor gaseous — and boasts a very highly effective power content material. “Engineers have been making an attempt for the reason that Nineteen Seventies to drill all the way down to this well-known stage at 3,000 meters in Larderello however they nonetheless haven’t succeeded,” explains Riccardo Minetto, a researcher in UNIGE’s Division of Earth Sciences. “What’s extra, we nonetheless don’t know precisely what this mattress is made up of: is it a transition between molten and stable rocks? Or does it include cooled granites releasing fluids trapped at this stage?” The expertise is turning into ever extra subtle. Due to this geothermal drilling in the hunt for supercritical circumstances has been tried as soon as extra at Larderello-Tavale. The intention? Deepening a wellbore few centimeters large to a depth of 3,000 meters to faucet these supercritical fluids. “This drilling, which fashioned a part of the European DESCRAMBLE mission, was distinctive as a result of it focused the advised transition between rocks in a stable and molten state,” continues professor Lupi.

The Geneva staff arrange eight seismic stations across the properly inside a radius of eight kilometers to measure the influence of the drilling on seismic exercise. Because the drilling progressed, the geophysicists collected the info and analyzed every issue that was encountered. “The excellent news is that for the very first time, drilling in the hunt for supercritical fluids brought on solely minimal seismic disturbance, which was a feat in such circumstances and a robust signal of the technological progress that has been made,” explains professor Lupi. His staff used the eight seismic stations to differentiate between the pure seismic exercise and the very weak occasions attributable to the drilling. The brink of 3,000 meters, nonetheless, was not reached. “The engineers needed to cease about 250 meters from this stage as a results of the extraordinarily high-temperature improve — over 500 levels. There’s nonetheless room for technical progress on this level,” says Minetto.

This examine signifies that the supercritical drilling went properly and that the expertise is near being mastered. “Till now, anybody who had tried to sink a properly in supercritical circumstances didn’t succeed due to the excessive temperatures however the outcomes listed here are extraordinarily encouraging,” says professor Lupi. Switzerland is itself very energetic in selling geothermal power. This renewable supply of power if developed additional would share a number of the burden of the nation’s hydropower, photo voltaic and windpower. “Geothermal power could possibly be one of many major sources of power of our future, so it’s solely proper to advertise future investments to develop it additional and safely,” concludes the Geneva-based researcher.

Reference: “Tectonic and Anthropogenic Microseismic Activity Whereas Drilling Towards Supercritical Situations within the Larderello‐Travale Geothermal Discipline, Italy” by Riccardo Minetto, Domenico Montanari, Thomas Planès, Marco Bonini, Chiara Del Ventisette, Verónica Antunes and Matteo Lupi, 26 January 2020, Journal of Geophysical Analysis.
DOI: 10.1029/2019JB018618

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