Meg Cichon, Associate Editor, RenewableEnergyWorld.com
July 16, 2013 | 8 Comments
New Hampshire, USA -- The U.S. geothermal industry recently scored a big win when its first enhanced geothermal system (EGS) project went online in April. ORMAT was able to stimulate a previously unproductive well at its Desert Peak project with EGS technology — injecting fluid into a well to reopen cracks and create a resource reservoir — and found an additional 1.2 megawatts (MW) of capacity. Renewable energy experts applauded the project, dubbing it a "game-changer" and a "shining moment" for the industry.
This article can be found in our completely redesigned Renewable Energy World digital magazine. Subscribe here to recieve a free copy.
Though the project represents a breakthrough for EGS technology and the geothermal industry in general, EGS has come under fire, with opponents accusing it as being just as dangerous as oil or natural gas hydraulic stimulation, commonly known as fracking. While traditional geothermal energy is viewed as clean renewable energy, could EGS technology, with its similar "fracking methodology," coupled with its rocky past, come under the same intensive scrutiny as natural gas fracking?
Back to Basics: What Is Geothermal Energy Anyway?
EGS and Earthquakes
Perhaps the most notorious EGS project is one that was never completed in Basel, Switzerland — constructed on a known seismic fault and suspended in 2006 when it generated earthquakes that reportedly caused millions of euros in damage to local infrastructure. The project was cancelled in 2009 after several reports said that if continued, it would cause more earthquakes and would lead to more damage each year.
"It's easy to generate a lot of fear. You can scare people about things without providing much solid information," said David Stowe, communications director at AltaRock. "The Basel story is dredged up over and over again — but we have learned from it, and it is pretty easy to put safeguards in place that will severely minimize risk."
Since its cancelation, many have pointed to the Basel project as a reason to avoid EGS altogether. However, the U.S. Department of Energy (DOE) remained undeterred, and developed geothermal-induced seismicity protocol and further stringent safety measures with Lawrence Berkley National Labs to prevent major seismic events - the only protocol in place for any sub-surface energy industry, according to Doug Hollet, director of the DOE geothermal energy program.
The DOE has been working on several EGS projects, including AltaRock's innovative Newberry project in Bend, Oregon. To ensure that the Newberry project does not cause significant seismic events, AltaRock has implemented rigorous protocols and created an advanced microseismic network system of about 20 seismometers that surrounds the project both on the surface and in wells 1,000 feet below the earth. The seismometers pick up the sounds that fractures make when they grow, triangulate and then displays the location of the fracture zone on a computer screen — AltaRock has its own modeling software for this, said Stowe.
"We have engineers outside monitoring pumps, two or three geologists on the command trail monitoring computer screens, and additional monitoring equipment," explained Stowe. "It's an intricate operation."
In natural gas, seismic activity is not the major concern when it comes to the fracking process. According to Stowe, the reinjection of the spent working fluid causes the most problems. "It creates a huge bulge when you re-inject all this water; pressure builds and the earth moves to compensate for that, which can cause a seismic event," said Stowe — adding, however, that this isn't a common occurrence.
According to Andrew Place, interim director and president of the Center for Sustainable Shale Development, seismicity is more of a concern for EGS due to the ongoing nature of the technology, whereas natural gas enters a site, fracks for the resource and moves on. "[For natural gas] the strong concern is for disposal wells, and if you don't site them carefully and drill in a close proximity to an existing fault that is highly stressed, you could set off a substantial seismic event," he said. This can be avoided with pre-drill modeling to ensure the avoidance of fracture networks and monitoring for seismic events — similar to the precautions already being taken at the Newberry project site.
Fracking vs Slipping
According to Hollett, the fundamental difference between natural gas fracking and EGS fracking is the injection process. The oil and gas industry injects water and a proppant (a mix of sand and chemicals), at a very high pressure of around 9,000 psi or more, which breaks though the rock and holds the cracks open; otherwise they would close when the fluid stops flowing.
EGS, however, uses water, and sometimes acid, to shear the rock and cause a "slip." "You're trying to make two rock faces slide past each other slightly, which creates a little bit more space between them," said Lauren Boyd, EGS program manager at the DOE. This is where fractures or weaknesses in the rock likely existed already and were plugged by mineral deposits over time. Boyd compared the process to putting an ice cube in a glass of hot liquid: "cracks will form where there are existing deformities in the ice, which is similar to what happens in the subsurface with closed fractures," she said.
As for long-term effects, "we are talking about very small fractures very deep in the earth — there is really little or negligible long-term impact there," said Hollett.
Since many believe EGS technology to be similar to natural gas fracking, the same concerns about leakage, spills and resulting groundwater and soil contamination exist for both technologies. After all, according to Popular Mechanics, in the past two years alone, natural gas fracking has caused numerous surface spills including several projects that have contaminated groundwater.
AltaRock plans to combat these problems at the Newberry project by using a multizone stimulation process. Water is injected into a single well at a pressure of about 2,000 psi to stimulate cracks in the rock, which eventually spider out to create a "zone." Once a zone is complete, pressure is dropped to 1,000 psi and a diverter made of biodegradable plastic (similar to plastic developed that allows water bottles to biodegrade in landfills) is injected into the well to "gum up" the cracks, according to Stowe. Pressure is then increased to 2,000 psi to start a new fracture zone, and then a new batch of diverter is made to plug up holes at hotter temperatures. The process repeats until all zones are created, and water flow is then stopped to allow the well to heat up. It takes about one week for the diverter to break down into water and CO2, which is eventually used to generate power once the plant is built, said Stowe.
According to several experts, many of the issues related to natural gas fracking can be prevented with the same type of proper protocol and procedures in use at the Newberry project. For example, in 2011 Chesapeake Energy reportedly lost control of a well in Pennsylvania. The well cracked, spilled and contaminated a nearby stream - this could have been prevented by using stronger cement and casings to ensure an impermeable seal.
The natural gas industry is slowly realizing that it needs to reduce these issues to gain public confidence, said Stowe, so it is working with state regulators to create some of the same regulations that exist for geothermal. Texas became the first state to require companies to reveal what is in its fracking solutions. And more recently, Illinois passed some of the "toughest fracking regulations" in the U.S., and will require companies to reveal chemicals used and test groundwater before and after fracking. "The best way to get around issues is to adequately fund state agencies, employ smart people with decades of experience, gain support from the surrounding regulatory framework and a commitment from the Environmental Protection Agency," said Place.
Though there are far fewer EGS projects compared to the thousands in natural gas, Hollett is confident that if the geothermal sector follows best practices, drills wells properly and works with regulatory agencies, it will mitigate the potential for any adverse environmental impacts.
Place agrees, and points out that both technologies have potential risks, neither of which are served well by avoiding them. Though there are different risk pathways, he said, risks are risks, and the industries not only needs strong regulations, but strong practices and responsible development — it "goes hand-in-hand" for both technologies.
"At Newberry [regulations are] rigorous - that's how it should be, and that's okay. Fracking should be completely safe, and if it isn't then someone is doing a sloppy job," said Stowe. "I'm hopeful that the natural gas industry will [work to create regulations and protocols], because in my opinion fracking is here to stay — I don't see it going anywhere any time soon."
Lead image courtesy AltaRock
With over 52,000 subscribers and a global readership in 174 countries around the world, Renewable Energy World Magazine covers industry, policy, technology, finance and markets for all renewable technologies. Content is aimed decision makers...