… Can enormous heat deep in the Earth be harnessed to provide energy for us on the surface? A promising report from a geothermal borehole project that accidentally struck magma–the same fiery, molten rock that spews from volcanoes–suggests it could.
The Icelandic Deep Drilling Project, IDDP, has been drilling shafts up to 5km deep in an attempt to harness the heat in the volcanic bedrock far below the surface of Iceland. But in 2009 a borehole at Krafla, Northeast Iceland, reached only 2,100m deep before unexpectedly striking a pocket of magma. The molten rock was intruding into the Earth’s upper crust from below at searing temperatures of 900 to 1000 degrees Celsius.
This borehole, IDDP-1, was the first in a series of wells drilled by the IDDP in Iceland looking for usable geothermal resources. A special report in this month’s Geothermics journal details the engineering feats and scientific results that came from the attempt to harness the incredible geothermal heat. (The only previous case like this was in Hawaii in 2007, but that well was sealed in concrete.)
Wilfred Elders, professor emeritus of geology at the University of California, Riverside, co-authored three of the research papers inGeothermics with Icelandic colleagues. “Drilling into magma is a very rare occurrence, and this is only the second known instance anywhere in the world,” Elders said. The IDDP and Iceland’s National Power Company, which operates theKrafla geothermal power plant nearby, decided to make a substantial investment to investigate the hole further.
This meant cementing a steel casing into the well, one with a perforated section at the bottom closest to the magma. Heat was allowed to slowly build in the borehole, and eventually superheated steam flowed up through the well for the next two years. Elders said that the success of the drilling was “amazing, to say the least,” adding, “This could lead to a revolution in the energy efficiency of high-temperature geothermal projects in the future.”
The hole funnelled superheated, high-pressure steam for months at temperatures of over 450 degrees Celsius–a world record. In comparison, geothermal resources in the UKrarely reach higher than around 60 to 80 degrees Celsius. The magma-heated steam was capable of generating 36MW of electrical power. While relatively modest compared to a typical 660MW coal-fired power station, this is more than half of the Krafla plant’s current 60MW output.
Most importantly, it demonstrated that it could be done. “Essentially, IDDP-1 is the world’s first magma-enhanced geothermal system, the first to supply heat directly from molten magma,” Elders said. The borehole was being set up to deliver steam directly into the Krafla power plant when a valve failed, which required the borehole to be stoppered. Elders added that, although the borehole had to be plugged, the aim is to repair it or drill another well nearby. …
Under the earth’s crust, the next layer down is not molten magma. This is a common misconception. The mantle is a very slowly flowing solid, silicate rocky shell about 1,800 miles thick.
Environments of magma formation and compositions are commonly correlated. Environments include subduction zones, continental rift zones, mid-ocean ridges and hot spots. Despite being found in such widespread locales, the bulk of the Earth’s crust and mantle is not molten. Rather, most of the Earth takes the form of a rheid, a form of solid that can move or deform under pressure. Magma, as liquid, preferentially forms in high temperature, low pressure environments within several kilometers of the Earth’s surface.
If we found a location where magma was flowing the right way, could we pump the water from Fukushima down into the magma and have only clean steam come back up?