An incandescent lava flow winds its way downslope from a vent at Iceland’s Krafla volcano. Credit: U.S. Geological Survey
drilling an exploratory geothermal well in 2009 in the Krafla volcano
in Iceland met with a big surprise: underground lava, also called magma,
flowed into the well at 2.1 kilometers (6,900 feet) depth.
It forced the scientists to stop drilling.
the best of our knowledge, only one previous instance has been
documented of magma flowing into a geothermal well while drilling,” said
Wilfred Elders, a geologist at the University of California, Riverside,
who led the research team.
scientists received $3.5 million from the National Science Foundation
(NSF), and $1.5 million from the International Continental Scientific
Drilling Program, to conduct their research.
and his team studied the well within the Krafla caldera as part of the
Iceland Deep Drilling Project, an industry-government consortium, to
test whether geothermal fluids at supercritical pressures and
temperatures could be exploited as sources of power, said Leonard
Johnson, program director in NSF’s Division of Earth Sciences, which
funded the research.
were drilling a well designed to search for very deep–4.5 kilometers
(15,000 feet)–geothermal resources in the volcano,” said Elders. “While
the magma flow interrupted our project, it gave us a unique opportunity
to test a very hot geothermal system as an energy source.”
a third of the electric power and 95 percent of home heating in Iceland
is produced from steam and hot water that occurs naturally in volcanic
economics of generating electric power from such geothermal steam
improves the higher its temperature and pressure,” Elders said.
you drill deeper into a hot zone, the temperature and pressure rise. It
should be possible to reach an environment where a denser fluid with
very high heat content–but also with unusually low viscosity
occurs–so-called ‘supercritical water.'”
such supercritical water is used in large coal-fired electric power
plants, he said, “no one had tried to use the supercritical water that
should occur naturally in the deeper zones of geothermal areas.”
and colleagues report in the March issue of the journal GEOLOGY,
published by the Geological Society of America, that although the Krafla
volcano, like other volcanoes in Iceland, is basaltic (a volcanic rock
containing 45-50 percent silica), the magma they encountered is a
rhyolite (a volcanic rock containing 65-70 percent silica).
The Iceland Drilling Company rig at the Krafla geothermal field; it drilled into molten magma. Credit: W. Elders, UC-Riverside
“Our analyses show that this magma formed by partial melting of basalts within the Krafla volcano,” Elders said.
“The occurrence of minor amounts of rhyolite in some basalt volcanoes has always been something of a puzzle.
had been inferred that some unknown process in the source area of
magmas, in the mantle deep below the crust of the Earth, allows a
silica-rich rhyolite melt to form–in addition to the dominant
silica-poor basalt magma.”
said that in geothermal systems water reacts with and alters the
composition of the rocks, a process termed “hydrothermal alteration.”
research shows that the rhyolite formed when a mantle-derived basaltic
magma encountered hydrothermally altered basalt, and partially melted
and assimilated that rock,” he said.
In the spring of 2009, Elders and colleagues progressed normally with drilling the well to 2 kilometers (6,600 feet) depth.
In the next 100 meters (330 feet), however, multiple acute drilling problems occurred.
drillers determined that at 2,104 meters (6,900 feet) depth, the rate
of penetration suddenly increased and the torque on the drilling
assembly increased, halting its rotation.
the drill string was pulled up more than 10 meters (33 feet) and
lowered again, the drill bit became stuck at 2,095 meters (6,875 feet).
intrusion of magma had filled the lowest 9 meters (30 feet) of the open
borehole. The team terminated the drilling and completed the hole as a
the well was tested high pressure dry steam flowed to the surface with a
temperature of 400 degrees Celsius or 750 degrees Fahrenheit, coming
from a depth shallower than the magma,” Elders said.
and colleagues estimated that this steam could generate 25 megawatts of
electricity if passed through a suitable turbine–enough electricity to
power 25,000 to 30,000 homes.
makes this well an attractive source of energy,” said Elders, “is that
typical high-temperature geothermal wells produce only 5 to 8 megawatts
of electricity from 300 degrees Celsius or 570 degrees Fahrenheit wet
believes it should be possible to find reasonably shallow bodies of
magma, elsewhere in Iceland and the world, wherever young volcanic rocks
“In the future these could become attractive sources of high-grade energy,” said Elders.
Iceland Deep Drilling Project has not abandoned the search for
supercritical geothermal resources. The project plans to drill a second
deep hole in southwest Iceland in 2013.
was joined in the research project by scientists at HS Orka hf (HS
Power Co.), Iceland; University of California, Davis; Stanford
University; Iceland GeoSurvey; Landsvirkjun Power, Iceland; U.S.
Geological Survey; New Mexico Institute of Mining and Technology; and
the University of Oregon, Eugene
Iceland Deep Drilling Project: http://iddp.is/
International Continental Scientific Drilling Program: /news/longurl.cfm?id=219