In 2009, geologists drilling an exploratory geothermal well in Iceland’s Krafla volcano encountered a problem for which they were simply unprepared – magma (molten rock or lava underground) flowed unexpectedly into the well at 6,900-foot depths, forcing the researchers to terminate the drilling. .
the best of our knowledge, only one previous instance of magma flowing into a
geothermal well while drilling has been documented," says Wilfred Elders,
a professor emeritus of geology in the Department of Earth Sciences at the
University of California, Riverside, who led the research team. "We were
drilling a well that was designed to search for very deep – 15,000 feet –
geothermal resources in the volcano. While the magma flow interrupted our
project, it gave us a unique opportunity to study the magma and 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 rocks.
economics of generating electric power from such geothermal steam improves the
higher its temperature and pressure," Elders explains. "As you drill
deeper into a hot zone, the temperature and pressure rise, so 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.' Although such supercritical water is used in large coal-fired electric
power plants, no one had tried to use supercritical water that should occur
naturally in the deeper zones of geothermal areas."
colleagues report in the March issue of Geology that
although the Krafla volcano, like all 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).
analyses show that this magma formed by partial melting of certain basalts
within the Krafla volcano," Elders says. "The occurrence of minor
amounts of rhyolite in some basalt volcanoes has always been something of a
puzzle. It had been inferred that some unknown process in the source area of
magmas, in the mantle deep below the crust of the Earth, allows some
silica-rich rhyolite melt to form in addition to the dominant silica-poor
explains that, in geothermal systems, water reacts with and alters the
composition of the rocks, a process termed "hydrothermal alteration."
"Our research shows that the rhyolite formed when a mantle-derived
basaltic magma encountered hydrothermally altered basalt, and partially melted
and assimilated that rock," he says.
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. Elders's research team received support of $3.5 million from
the National Science Foundation and $1.5 million from the International
Continental Scientific Drilling Program.
spring of 2009, Elders and his colleagues progressed normally with drilling the
well to 6,600-foot depths. In the next 330 feet, however, multiple acute
drilling problems occurred. In June 2009, the drillers determined that at 6,900
feet, the rate of penetration suddenly increased, and the torque on the
drilling assembly increased, halting its rotation. When the drill string was
pulled up more than 33 feet and lowered again, the drill bit became stuck at 6,875
feet. An intrusion of magma had filled the lowest 30 feet of the open borehole.
The team terminated the drilling, and completed the hole as a production well.
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 says. "We estimated that this
steam could generate 25 megawatts of electricity if passed through a suitable
turbine, which is enough electricity to power 25,000 to 30,000 homes. What
makes this well an attractive source of energy is that typical high-temperature
geothermal wells produce only 5 to 8 megawatts of electricity from 300 Celsius
or 570 Fahrenheit wet steam."
believes it should be possible to find reasonably shallow bodies of magma, elsewhere
in Iceland and the world, wherever young volcanic rocks occur.
the future, these could become attractive sources of high-grade energy," says
Elders, who got involved in the project in 2000 when a group of Icelandic
engineers and scientists invited him to join them to explore concepts of
developing geothermal energy.
Iceland Deep Drilling Project has not abandoned the search for supercritical
geothermal resources. The project plans to drill a second deep hole in
When Magma Flowed into a Borehole
February 17, 2011