GE (NYSE: GE) Global Research today announced it has signed a contract with the National Energy Technology Laboratory (NETL), part of the U.S. Department of Energy (DOE) national laboratory system, to build a multi-point sensing system to monitor carbon dioxide (CO2) injected into geothermal containment wells. The use of these cavities, which extend 1-2 kilometers below the surface of the Earth, is being explored by the federal government and power producers as an option for the long-term storage of CO2.
Carbon dioxide emitted from the combustion of fossil fuels has long been an environmental concern. It represents 84% of U.S. greenhouse gases, according to a 2010 analysis by the U.S. Environmental Protection Agency. Carbon capture and sequestration of highly pressurized CO2 in underground wells is viewed as a promising alternative to the release of CO2 gas into the atmosphere.
Highly accurate monitoring, verification and accounting are critically important to ensure that CO2 pumped underground is confined to the potentially porous or fractured rock that contains each well. Currently, GE is testing a fiber-optic cable with a sensor that can measure temperature and pressure at a single point inside the well. Readings from that pressure sensor have been calibrated to an accuracy of ±0.1%. This follow-up project would add a yet-to-be-determined number of additional sensors along the length of a multi-kilometer cable, enabling engineers to track the disbursement and movement of CO2 within the sequestration well with even greater precision.
“Our goal is to develop an incredibly resilient cable and sensor system that can withstand an extremely harsh environment for an extended period of time—temperatures as hot as 250°C and pressures topping 10,000 psi,” said Dr. William Challener, principal investigator and physicist in the Photonics Lab at GE Global Research. “The work is very challenging. We have already developed a single sensor system that can tolerate temperatures as high as 374°C and 3,000 psi for short periods. Now, we’ll leverage that knowledge to build a package that is even more robust and that can be multiplexed along the cable.”
To illustrate how extreme these underground conditions are, Challener noted that 250°C is about 40% hotter than boiling water and 10,000 psi is equivalent to the pressure encountered 4.25 miles under the ocean. Additionally, some high-power industrial power washers exert a pressure of 10,000 psi and those are capable of slicing metal and concrete.
Another key component of the project is wireless communication. GE scientists will develop a remote monitoring system capable of activating and operating the sensors from an off-site control room.
“The end-goal is to ensure confidence in the long-term stability of CO2 sequestration sites,” said Challener. “We believe the fiber-optic cable and sensing system we’re tasked with fabricating will help make that goal a reality.”
Work on the 2-year, $1.2 million joint venture between GE Global Research and NETL is slated to get underway in January, 2013.
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