Enhanced Geothermal Systems
Enhanced or engineered geothermal systems (EGS), frac’ing or fracking programs, hydraulic shearing…call it what you want, but our ability to alter rock reservoirs has the power to change the geothermal energy industry.
Conventional geothermal energy programs need three things to be successful:
1. Heat. Without this you don’t have a resource.
2. A transfer medium. Required to transfer the heat; this is usually water.
3. A rock environment. With enough porosity to move the heat through.
In the simplest terms, if a geothermal energy developer can move enough water through hot, fractured, or porous rock, he or she can use that heat to power a turbine—and, therefore, has a potential power project. Seems simple enough, right? But, what if this incredible heat resource is trapped in solid rock? One can’t economically move heat out of a solid rock thousands of meters underground. So, should such a developer simply walk away from the potential project or work to improve the situation?
The oil and gas industry had a similar problem with getting precious oil and gas resources out of tight formations. They knew these energy resources were in certain rock but, at first, couldn’t feasibly or economically recover it. However, there was a solution. Fluid-driven fractures could be formed at depth in the oilfield borehole and extended into targeted aquifer formations. Frac’ing or Fracking technology significantly increased the surface area to recover the petroleum resources, and is now commonly used by the oil and gas industry to access “unconventional” natural gas deposits trapped in shale, coalbed, and tight-sand formations. Add in the ability to drill horizontally within the right formation and the oil and gas industry exponentially improved petroleum recovery in that formation.
Even for the geothermal industry, the cat is already out of the bag. Many geothermal energy developers have already begun to see the potential of similiar technology. Projects in Soultz France, Cooper Basin, Australia, and Newberry, in the US have all used pressured fluids to increase permeability and to increase heat recovery. In hard-rock and volcanic environments, man-made hydraulic fractures use internal fluid pressure to help open pre-existing weakness in the rock structure. The new fracture is then typically maintained by introducing a proppant (such as sand, ceramic, or particulates) into the injected fluid.
Projects that were once left economically wanting now have the potential for increased profitability. And, those in the renewable energy industry understand that slight improvement could take a project into the realm of financial viable.
This technology is not without its’ detractors, however. Environmental and community groups have brought some of the technology’s downfalls into the public spotlight. Fresh water contamination, induced seismicity, and the toxic nature of some fracking fluids are just some of the concerns. To continue to be part of a clean energy solution for our planet, the geothermal energy developers adopting this technology need to closely monitor and responsibly deal with any and all concerns, real or imagined. The industry needs to ensure that any individual fracking program does leave a “black eye” on the geothermal industry as a whole.
At the core, our planet is over 5,000°C and is approximately 6.3km thick and continues to produce vast amounts of heat. To put this in perspective; the heat stored in the only the top 3 km of the continental crust is equivalent to the energy consumed by mankind for some 100,000 years at the present rate. At a depth of 10km, the heat in the of the earth’s crust contains 50,000 times as much energy as found in all the world’s oil and gas reserves combined. In 2007, a US Department of Energy sponsored study, completed by independent experts led by the Massachusetts Institute of Technology (MIT), concluded that geothermal energy could provide 100,000 MWe or more in 50 years by using advanced EGS (enhanced geothermal energy) technology.
The problem is clearly not a lack of heat (we have billions of years of heat available), it is getting that heat out of the ground cost effectively. The more the industry can research and test this technology in geothermal applications, the more this technology can be implementing to improve the economics and decrease the project risks of geothermal energy development. Love it or hate it, fracking technology has the potential to forever change how the geothermal energy industry extracts its’ heat resource.
This article was written for North America Clean Energy Magazine for November 2010
Author: Craig Dunn is a pioneer in geothermal energy exploration and development initiatives in Canada, with expertise in the industry’s efforts on developing high-temperature geothermal energy from untapped resources.