Using Nanoparticles as Tracers to Characterize Fractured Rocks

The Stanford Geothermal Program had a noteworthy result this week, having achieved a proof of concept in the use of tiny particles called nanoparticles as tracers to characterize fractured rocks. The result comes from research funded by DOE in 2008 to accelerate technology development for Enhanced Geothermal Systems (EGS). This research will help developers learn more about the fracture systems in geothermal reservoirs, so that they may better predict the results of reservoir stimulation. Positive results from DOE-funded research will lead to further development of EGS, a clean energy technology capable of producing baseload electricity across the United States.

The ultimate goal of the Stanford project is to utilize the nanoparticles as sensors to characterize subsurface fractures. The initial experimentation with nanoparticle injection served as a basic milestone of this vision. It was essential to verify the possibility of recovering the nanoparticles following their injection, and to demonstrate that they were not trapped in the pore spaces by hydraulic, chemical or electrostatic effects. To investigate these issues, a nanofluid was created by suspending SiO2 nanoparticles in a liquid solution, and then injecting into a Berea sandstone core. The injected nanoparticles were transported through the pore space of the rock and were detected and recovered in the effluent.

For more information on DOE's Geothermal Technologies Program, visit the Geothermal Technologies Program Web site.