Preliminary tests performed at an exploratory well last year suggest high-pressure, dry steam created by the heat of underground lava -- steam topping 400 degrees Celsius -- could generate 25 MW of electricity, enough electricity to power 25,000 to 30,000 homes.
The discovery raised the prospect of using such shallow intrusions of magma directly as a source of geothermal energy.
“To the best of our knowledge, only one previous instance has been documented of magma flowing into a geothermal well while drilling,” said research geologist Wilfred A. Elders, who with Gudmundur Omar Fridleifsson led the scientific team whose work at the site two years ago paved the way for the pilot plant.
The plant itself was built and is being run by Landsvirkjun, the operating company at the Krakla caldera. Landsvirkjun Project Manager Bjarni Palssen is supervising the team that will conduct flow tests at the well and ultimately develop the resource.
Elders, a geologist at the University of California, Riverside in the US, had travelled with an international team to the Krafla caldera in search of supercritical geothermal resources -- subterranean fluids at enormous pressures and temperatures that could be exploited as sources of power.
But after about five weeks of drilling and at a depth of 2.1 kilometres (6,900 feet), they suddenly began to encounter trouble.
The first two kilometres of drilling went fine. But every time they attempted to go another 100 metres (330 feet), multiple acute drilling problems occurred.
“The simplest way to describe it is, the drill bit kept getting stuck,” Elders said during a recent interview with Renewable Energy Magazine. “In fact, it got stuck so badly a couple of times that it twisted off and we had to side track the hole.”
Drillers persevered, but on the next try, the rate of penetration suddenly increased and the torque on the drilling assembly increased, halting its rotation. Much to their surprise however, “buckets and buckets of glass” began coming to the surface, Elders said.
“That’s when we realized that what was happening was that magma had flowed into the well and was freezing around the drill head assembly, a process that was creating the glass,” he said.
Then they succeeded in pulling the drill up and ran down to try again, but it was to no avail.
In fact, an intrusion of magma had filled the lowest nine metres (30 feet) of the open borehole. Because of the magma, the team could go no further.
At the same time, however, they realized they’d been presented with a golden opportunity, and completed the hole as a production well.
Team comes together at Geothermal Congress
Elders, has been working in the realm of high temperature geothermal systems for the last 30 years, and has long understood that the economics of generating electric power from geothermal steam improves the higher its temperature and pressure.
“As you drill deeper into a hot zone, the temperature and pressure rise,” he said. “Therefore, 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, Elders continued, “no one had tried to use the supercritical water that should occur naturally in the deeper zones of geothermal areas”.
“Our modelling suggested that if we could drill to super critical fluid, we could get flow rates which are very high and a very hot fluid, which, as you decompressed it and it came up the well, would turn it into a superheated steam, which could be passed directly into a turbine,” he said.
Then came 2000 World Geothermal Congress in Japan, a meeting at which Elders had conversations about the prospects for supercritical geothermal with like-minded engineers then in the early planning stages of their own geothermal effort in Iceland.
“They invited me to join them and put together a science program to buttress the engineering that they were talking about, along with my Icelandic colleague Gudmundur Omar Fridleifsson. The project was funded by a consortium of industrial companies, including the three principal power companies in Iceland: Hitaveita Sudurnesja (since 2008: HS Orka hf), Landsvirkjun and Orkuveita Reykjavíkur , and Orkustofnun, the National Energy Authority of Iceland.
Other corporate partners included Alcoa, the international aluminum company, and Statoil, the Norwegian national oil company.
The consortium became known as the Iceland Deep Drilling Project. In addition to funds for drilling provided by IDDP, the science program received $3.5 million from the US National Science Foundation, and an additional $1.5 million from the International Continental Scientific Drilling Program.
"The magma flow interrupted our project, keeping us from reaching sufficient depth to get the pressures necessary to induce he supercritical state, but it’s giving us a unique opportunity to test a very hot geothermal system as an energy source," Elders said.
Questions remain
The decision to establish a pilot plant at the site follows three months of testing by the team, during which they found that high pressure dry steam flowed to the surface with a temperature of 400 degrees Celsius (750 degrees Fahrenheit), coming from a depth shallower than the magma.
"What 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 steam."
He believes it should be possible to find reasonably shallow bodies of magma, elsewhere in Iceland and the world, wherever young volcanic rocks occur.
“However, there are still a lot of questions to be answered before we can get economically viable energy from it,” Elders said. “First, we need to identify those areas where magma occurs at drillable depths, then we need to learn how to drill into it, and then, once there, we need to determine how to get energy from it.”
“One way would be to drill pairs of wells into the magma and pump cold water under pressure down one to freeze the magma and fracture the glass that’s then produced, and then drill a well into those fractures and extract the supper heated steam from the second well,” he said.
A better option than that EGS?
Elders’ work comes at a time when the big push in the geothermal world is for Enhanced Geothermal Systems (EGS), a genre of geothermal power technologies that do not require natural convective hydrothermal resources.
Until recently, geothermal power systems have only exploited resources where naturally occurring water and rock porosity is sufficient to carry heat to the surface. However, the vast majority of geothermal energy within drilling reach is in dry and non-porous rock. EGS technologies “enhance” or create geothermal resources in this hot dry rock through hydraulic stimulation – in effect, the same “two-well” process Elders believes might prove effective with magma.
Currently there are EGS systems currently being developed and tested in France, Australia, Japan, Germany, the US and Switzerland. Mostly in rock about 200 degrees Celsius (392 degrees Fahrenheit) and four to five kilometres beneath the Earth.
The largest of these is a 25 megawatt demonstration plant currently being developed in the Cooper Basin, Australia, while the most successful – in that it has been connected to the grid – is a 1.5 MW demonstration plant at Soultz-sous-Forêts, France.
“I haven’t had any direct involvement on the EGS side of things, but I can tell you that level of power production is very low compared to what we get from a conventional geothermal well in a high temperature field such as those found in Italy, the Philippines, Indonesia, Japan, New Zealand, and, of course, Iceland,” Elders said.
The geologist went on to say that because the temperatures are relatively low, the engineered systems would, in general, not be making steam that could be directly fed through a turbine, but would instead have to rely on a heat exchanger at the surface.
These so-called “binary plants” use the heat from the rocks below to convert liquid hydrocarbons in the exchanger to vapour. These hydrocarbon vapours pass through the turbine to generate electricity, but with a considerable amount of energy loss due to the heat exchange process itself and the amount of power needed to pump the hydrocarbons around.
Which is not to say tapping magma for energy is not also without its challenges: As Elders was quick to point out, “no one’s really done it before, so we’ll have to develop the necessary technology”.
“There was a magma energy program within the US Dept. of Energy 20 years ago, but it never got very far,” he said.
Elders said the first program that needs to be solved is how to drill into magma and keep the hole open.
“You have to be able to cool it sufficiently to create that body of glass that you can drill into and that remain open after you pull the drill out,” he said.
A second problem is dealing with the acid gases that magma gives off.
“One way to deal with that is to keep the gases coming off the magma superheated,” he said. “The acid from magma only becomes corrosive if it is absorbed in water. As long as you just have dry steam, that won’t be a problem.
“The other thing you can do is modify the pH in an injection well, but that would be expensive,” Elders added.
As work in preparation of tests at the pilot plant continue, Elders said he believes the 400 degree Celsius temperatures his team identified suggest the magma has yet to be breached directly.
“It’s very likely the steam we’re measuring is from water in a zone above the magma, and the reason we think that is we believe the magma should be closer to 900 degrees Celsius,” he said. “Still, 400 degrees Celsius is definitely wonderful.”
“The key to the success of the test will be how well we deal with the steam underground,” Elders added. “That’s because the deeper you go, the higher the pressure, and the higher the pressure, the more efficient the turbine producing the energy.”
The quest for supercritical to continue
All of which is not to suggest that Elders and his team has given up its quest for supercritical geothermal fluid. The project plans to drill a second deep hole – likely four to five kilometres deep -- at Reykjanes in southwest Iceland in 2013.
“The concept is still on the table,” Elders said. “All we’re waiting on now is funding and permitting and so on.”
Why not just be satisfied with the promise of magma?
Elders said because some “very strange” and “interesting” things occur as a liquid reaches the supercritical point that could make it an even more advantageous substance when it comes to geothermal energy production.
“Basically, the ratio between density and viscosity becomes very favourable for having very high flow rates,” he said. “All things being equal, in terms of well size, these very high flow rates would result in your getting much more energy out of the well.”
Elders seemed bemused by the attention his two-year-old drilling project is getting today, mainly as a result of a belatedly released statement on the project from the National Science Foundation. In fact, he seemed mildly mystified by it as he spoke to REM.
“What I hope it means is that people have gotten more attuned to renewable energy, and that people are beginning to recognize that geothermal is a renewable energy source that has a lot of attractiveness relative to wind and solar,” he said.
“Geothermal is ideal for base-load power, it operates 24 hours a day, seven days a week, 365 days a year, and you only need to close it down for maintenance every year-and-a-half, compared to the vagaries of much more frequent maintenance and repair associated with wind and solar.”
“Another thing is, geothermal wells have a much smaller environmental footprint per megawatt than solar and wind facilities do,” he said.
Best of all, the supercritical conditions Elders hopes to tap should exist in high temperature geothermal fields all over the world.
“That’s why I think if our project in Iceland is ultimately successful in generating steam from supercritical resources, it would have lots of applications in other countries and regions where you have high temperature systems, like New Zealand, the Andes, Central America, Western North America, the Aleutian Islands in the Northern Pacific Ocean, the Kamchatka Peninsula of Japan, and the Philippines, as well as places like Italy and Greece, where you have young volcanoes,” Elders said.
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