Researchers will soon attempt for the second time to tap into the rich geothermal potential of supercritical hydrous fluid by drilling into the igneous rocks of a volcanic crater in Iceland. Wikimedia Commons/ Batintherain
Researchers plan a second attempt to harness supercritical hydrous fluid from volcanic craters to drive steam turbines, generating electricity.
February 18, 2014—Later this year, a team of researchers and engineers will begin drilling into the igneous rocks of a caldera—or volcanic crater—in southwestern Iceland in a second attempt to reach a depth of 4.5 km. The team is working to reach supercritical hydrous fluid—fluid at the point of extreme pressure and temperature at which distinct phases of liquid and vapor do not exist.
The team hopes to harness this supercritical hydrous fluid, decompress it, and use the resultant steam to drive turbines, generating electricity, according to Wilfred A. Elders, Ph.D., a professor of geology emeritus and a research professor at the University of California, Riverside.
“Rocks begin to melt at [greater than] 700° C to 1,000° C,” Elders said in written comments to Civil Engineering online. “So there is an enormous energy potential—orders of magnitude greater that can be produced from conventional geothermal systems at 200°-300°C. However, places where we can safely drill into magma are quite rare and are restricted to active volcanoes.”
The expedition is the work of the Iceland Deep Drilling Project (IDDP), Reykjanesbær, Iceland, a consortium of the National Energy Authority of Iceland, four of the country’s largest energy companies, and Alcoa. In addition to consortium members, the International Continental Scientific Drilling Program and the National Science Foundation have also provided funding for the project.
The drilling project, IDDP-2, follows an earlier attempt, IDDP-1, in Krafla, a volcanic crater in northern Iceland. The drilling of IDDP-1 progressed slowly in 2009.
“The problem was the very high thermal gradients that caused slumping and caving, which slowed the drilling, increasing the costs,” Elders said. “The drilling assembly kept getting stuck as the hole neared the magma, probably due to the rock failure [caused by] thermal stresses. The drilling assembly became irretrievably stuck three times, and led to twist offs that required side tracking the hole twice.”
IDDP-1 was drilled to a depth of 2.1 km before the bit unexpectedly tapped into a pocket of 900° C magma. The lowest 20 m of the hole plugged with obsidian glass. Because of the earlier drilling difficulties, the well was already cased to nearly 2,000 m deep. The well was then completed as a subcritical installation and has successfully produced superheated steam since November 2011.
“We did not reach our target depth to reach supercritical water, but if you drill into a lemon you can make lemonade,” Elders said of the first well and the lessons learned.
The abundant volcanos and geysers in Iceland make it a natural location to test this technology. Geothermal energy is common in Iceland, a subpolar oceanic climate where average high temperatures in summer are about 58 ° F and winter lows average approximately 22 ° F. Harnessing supercritical water to generate electricity holds the promise of greatly increasing geothermal efficiency.
The technology also has the potential to create an environmentally benign, renewable energy source that produces much more energy than conventional geothermal systems. Developers also hope the project will increase knowledge about the interaction of geologic forces at work at such depths.
Beyond the difficulties the team has experienced in drilling, significant engineering challenges remain to harness supercritical hydrous fluid from volcanic regions. Handling high temperature, high pressure fluids that contain some acid gas will require expensive well head assemblies and valves, Elders said. The steam will need to be scrubbed before it enters the turbine.
“This technology is in its infancy,” Elders said. “The only limitation is raising the funds to pursue our goals expeditiously.”
Drilling of IDDP-2 will likely take five months, Elders said. IDDP feasibility studies suggest coring such a well would cost $6 million and developing a production well could cost a total of $9 million. Fluid handling and evaluation is projected to cost another $5.5 million.
The project is detailed in the January 2014 issue of the journal Geothermics.