鈥淭HIS is our gold,鈥� Gudmundur Omar Fridleifsson beams, as steam rising from the ground mists up his glasses. 鈥淕eothermal, hydrogen鈥nd fish.鈥� The wind changes direction and we get a sulphurous lungful. 鈥淚n Iceland we call this 鈥榯he pleasant smell鈥�,鈥� he adds.
The first thing you notice about Iceland are the bleak, moss-covered lava flows overlooked by black, snow-tipped volcanoes. The second is the smell. The shower in the hotel, much like the steam enveloping us now, has a distinctly eggy whiff. Hardly surprising when you consider that most of Iceland鈥檚 domestic hot water is heated deep underground and piped straight to the bathroom. According to Fridleifsson, sulphur is good because it helps stop the water pipes from rusting. It certainly stops visitors spending too long in the shower.
In a way, it is pipework that has brought me here: Fridleifsson is the manager of the Iceland Deep Drilling Project (IDDP). This ambitious scheme of extreme plumbing aims to bring unfeasibly hot fluids to the surface where we can reap the benefits of their energy. And it will make the geothermal well we鈥檙e standing beside, and every other well, seem like little more than a scratch on the Earth鈥檚 surface.
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The project aims to drill down 5 kilometres and extract energy from magma. Rather than dealing with molten rock directly though, Fridleifsson wants to tap into a reservoir of water which has come into contact with the magma and, thanks to the high temperatures and pressures at this depth, gone beyond steam to form a 鈥渟upercritical鈥� fluid. This is tricky stuff to handle: it has properties of both liquid and gas, and is an excellent solvent.
In fact, this fluid will be chock-full of metals and minerals, which can precipitate out at the drop of a hat, blocking pipes and creating a risk of blowout. But most important, this supercritical fluid has a greater heat content per unit of mass than steam from conventional wells. The sums suggest that a supercritical well should yield anything up to 10 times more energy than its steam-based counterparts. And while drilling down 5 kilometres has been done before, this will be the first time anyone in the world has set out to go supercritical.
The project also promises to tackle some of the world鈥檚 biggest geological and environmental questions. Thanks to the chemistry of supercritical fluids, this well could kick-start the global hydrogen economy and create the first sustainable mine 鈥� one that squirts precious metals and minerals up from the depths like a fountain. It will even give geologists their first peek inside the mid-Atlantic ridge and reveal the chemistry of mysterious vents called black smokers, which are usually only found deep beneath the ocean, without the need to touch the delicate ecosystems they support.
The IDDP started life in a mid-blizzard chat between Fridleifsson, then working as a well-site geologist, and Albert Albertsson, of the Icelandic energy company Sudurnes Regional Heating. 鈥淚t was about 11 pm, and the weather was very dramatic,鈥� Fridleifsson recalls. 鈥淎lbert and I were chatting at a well site. We started talking about deep drilling and supercritical fluids and it turned out that we were both really keen on the idea. Albert was the one who wanted to tame the beast,鈥� he says. The pair were so taken with the idea that they proposed the project at the World Geothermal Congress in Japan in 2000.
Since then, feasibility studies have shown that drilling into this kind of hot, high-pressure liquid is technically possible. The project has also won support from a consortium of Iceland鈥檚 three largest energy companies, including Sudurnes Regional Heating, and in December 2003, Sudurnes Regional Heating agreed to allocate one of its planned wells to the IDDP, in effect stumping up a fifth of the $15 million it will take to complete the project. The first 2.5 kilometres will be drilled in January next year. It will be extended to 4 kilometres in 2006, and to the final depth of 5 kilometres in 2007.
As test sites for deep drilling go, Iceland is one of the best. Formed where a mantle plume coincides with the mid-Atlantic ridge, an underwater mountain range where new crust is constantly created, it is one of the most geologically active regions in the world (快猫短视频, 8 March 2003, p 32). The Icelanders have made good use of this: the first geothermal well was drilled in 1928 and today 99 per cent of the people in the capital, Reykjavik, and nearly 90 per cent of the entire population, use geothermal energy to heat their homes. Fruit and vegetables are grown in geothermally heated greenhouses. They even farm fish, using naturally heated water.
Healthy effluent
On our way across the Reykjanes peninsula in the south-west, we stop at the Svartsengi power station which provides water and electricity for the Sudurnes region and take a dip in the plant鈥檚 famously healthy effluent, the Blue Lagoon. Somehow we manage to carry on talking science while covered in an exfoliating mixture of white silica mud and algae.
A couple of hours later and looking 10 years younger, we reach the IDDP site. There is not much to see yet except a colony of Arctic terns nesting amid the lava flows, but by next year it will be the scene of a very different activity.
Reykjanes was chosen because it is here that the mid-Atlantic ridge makes landfall. As a result, molten lava is closer to the surface here than almost anywhere else. Frequent earthquakes have cracked the rock, allowing rain and seawater to seep downwards to where it is heated. The evidence for this is all around us. Mud boils on the surface and steam escapes from every fissure. It is easy to see why Viking settlers named this flat expanse of lava Reykjanes 鈥� 鈥渢he steamy peninsula鈥�.
Most geothermal wells tap energy from a mix of boiling water and steam formed underground at temperatures between 200 掳C and 340 掳C. The steam is separated and passed through a turbine at the surface. However, Fridleifsson plans to drill through this region and go straight to the source of the heat. To extract energy from magma he must devise a convenient way of getting its heat to the turbine: the magma itself is far too hot. So, says Grimur Bjornsson, an engineer at the Reykjavik-based research institute Iceland Geosurvey, the IDDP will use water that sits in a reservoir directly on top of the magma. The extreme conditions encountered here change it into a supercritical fluid: a mix of liquid-like, hydrogen-bonded clusters of water molecules dispersed in a gas-like phase that makes an excellent solvent for all kinds of chemicals. It is this supercritical fluid that will be sent up through the well to the turbine, Bjornsson says.
Tapping this resource will be far from easy. When the words 鈥渟upercritical鈥� and 鈥渄rilling鈥� go together, they are usually followed by 鈥渋ncident鈥�. A well in Nesjavellir, just outside Reykjavik, accidentally hit supercritical fluid in 1985 and had to be plugged with 600 metres of gravel to stop the system blowing out. Supercritical conditions have also caused problems in high-temperature wells in Japan and Italy.
So the IDDP well head will be designed to handle fluid pressures of more than 220 bars and the well itself will be lined with three layers of cemented steel casing for over half its length. The casing will have to be carefully designed to handle the expansion caused by temperatures ranging from 30 掳C to more than 500 掳C. Geologists usually try to avoid drilling into material at high temperatures. Recently, one well in Iceland accidentally drilled into high-pressure steam at 380 掳C, 鈥渁lthough we didn鈥檛 know it at the time,鈥� Bjornsson says.
At each stage of drilling, the well fluid will be sampled, and the flow rate through the well measured. These will be crucial moments; if there isn鈥檛 enough pressure from below to drive the fluid upwards, the well will be useless. If the fluid is too cool, they鈥檒l end up with a very expensive, but conventional, geothermal well. But if all goes to plan and they hit supercritical conditions as expected, the fluid will be piped up for testing. Then all they have to do is work out how to deal with it.
鈥淧art of the problem is that we don鈥檛 know what temperatures and pressures to expect, and even less what the chemical composition will be,鈥� says Jon Orn Bjarnason of Iceland Geosurvey. 鈥淲e鈥檝e been drilling to 2 kilometres for decades so we pretty much know what the fluids will be at that depth. What we find at 5 kilometres 鈥� that鈥檚 a little different.鈥�
Most speculate that they will meet hot, high-pressure seawater modified by boiling and reacting with surrounding rock. It will contain all kinds of chemicals such as potassium, chlorides and calcium, plus pretty much any metal you care to think of. This could cause some headaches.
Conventional wells get slowly furred up by mineral deposits in the pipes, leaving them blocked like old arteries. But supercritical fluid could turn out to be the hard water from hell. If its temperature or pressure drops too far, or it mixes with cooler steam, minerals and metals could suddenly precipitate out. This could seal the pipes entirely, causing a build-up of pressure and a blowout that could destroy the well. The trick will be to control the pressure at the top of well and the speed of fluid flowing to the surface. 鈥淚t鈥檚 not a case of keeping out the harmful minerals, it鈥檚 a matter of controlling the conditions of production so that they don鈥檛 precipitate where you don鈥檛 want them to,鈥� says Robert Fournier of the US Geological Survey, one of the project鈥檚 scientific advisers.
If they manage to tame the fluid, converting its energy into electricity using a turbine should be relatively easy. 鈥淚f we can convert supercritical fluid to superheated steam we are in business,鈥� says Fridleifsson. 鈥淪team is something we are used to.鈥� The only difference is that while a flow of 2 kilograms per second of conventional steam produces 1 megawatt of power, the same flow rate of supercritical steam could, theoretically, generate 10 megawatts.
With an energy source this efficient, it will be even cheaper to produce hydrogen, by electrolysing water, to fuel Iceland鈥檚 clean-energy revolution. Iceland鈥檚 commitment to hydrogen is already clear. The world鈥檚 first hydrogen filling station opened just outside Reykjavik in April 2003 to fuel three city buses. There are plans to convert the entire fishing fleet, and eventually the whole country, to run on hydrogen. But could going supercritical convert the rest of the world too?
Possibly. Turning hydrogen into a global commodity relies on finding a cheap way to produce it and a safe way to transport it. Supercritical fluids could offer a solution to both problems. 鈥淎t temperatures above 400 掳C, what are known as 鈥榮upercritical water processes鈥� become possible,鈥� says Dan Fraser of the University of Manitoba in Canada.
Fraser thinks it should be possible to use a process called 鈥渟upercritical water partial oxidation鈥� to catalyse a reaction that transforms organic material 鈥� present in the fluid from the mine or added later 鈥� to create hydrogen directly. He also believes it is possible to efficiently convert carbon dioxide and hydrogen into methanol, which can be shipped around the world and is easily broken down into hydrogen when required.
Global hotspots
Better still, geothermal hotspots like Reykjanes are not unique to Iceland. Fraser鈥檚 group is working on a similar project in the Aleutian Islands, and other potential sites exist in the Great Rift Valley in Africa, Italy, Mexico, Costa Rica, Hawaii, California, Nicaragua, Japan and New Zealand: in fact, wherever there are young volcanic rocks. If the IDDP is successful, its technology could be applied worldwide.
But there is much more to the IDDP than just cheap energy and hydrogen production (see 鈥淐ore benefits鈥�). The same metals that could cause problems in the plumbing might turn out to be as profitable as the production of energy 鈥� if not more so. Fraser鈥檚 group is awaiting a patent on a system to extract metals from supercritical fluids, based on the sudden precipitation that occurs when supercritical fluid meets cold water. This process has already been observed around black smokers. If geologists can recreate it at the well head, geologically active countries could become huge stores of clean energy, as well as finding themselves quite literally sitting on a gold mine 鈥� and a sustainable one at that. 鈥淚f you鈥檙e drilling supercritical, pretty much the whole periodic table could come up. Third World countries could suddenly have resources of gold, silver, copper and zinc,鈥� Fraser says.
But no one is certain that this form of mining will succeed, and for now the ever-pragmatic IDDP team is focusing on the job in hand: to reach a depth of 5 kilometres safely. Geologists, engineers and environmentalists are all watching closely. Listening to the international experts who have gathered in Iceland to discuss the science, it is clear that no one is sure what they will encounter at that depth. 鈥淎fter hearing so many eminent scientists with different views, you think, well, we just don鈥檛 know,鈥� Bjarnason says at the end of the two-day meeting. Like everyone else involved, he can see only one way of finding out 鈥� by drilling that hole.
Core benefits
When the Iceland Deep Drilling Project was announced at the World Geothermal Conference four years ago, scientists around the world pricked up their ears. Geologists in particular spied an opportunity to make the most of what the Icelanders had in mind. 鈥淭he mid-ocean ridge is one of the major features of the planet, and we could get 2 kilometres of core through the transition from upper to lower crust,鈥� says Wilfred Elders, a geologist at the University of California, Riverside and one of the IDDP鈥檚 principal investigators. This core would provide insights into an environment where an oceanic plate is forming.
Iceland is also one of the best places to study an active mid-ocean ridge without the expense and complication of having to drill at sea. 鈥淰ery little is known about the fluid and rock interaction at these depths. At the moment we only have theories,鈥� says Alister Skinner of the British Geological Survey.
But it is not only geologists who are interested. Since deep-sea hydrothermal vents, or black smokers, were discovered in the late 1970s, scientists have been fascinated by these unique chemical factories found on ocean ridges. They create towering deposits of ores and, remarkably, manage to sustain life. If there is a supercritical reservoir underneath Reykjanes, it could be used as a laboratory for studying metal transport in supercritical fluid, exactly as it happens in black smokers. 鈥淭he results will be of global significance,鈥� Elders says.