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Carbon dioxide sequestration underground laser based detection system

Carbon dioxide (CO2) is a known greenhouse gas. Due to the burning of fossil fuels by industrial and power plants the atmospheric concentration of CO2 has been rising over the past 50 years. Carbon capture and sequestration provides a method to prevent CO2 from being emitted into the atmosphere. Successful carbon sequestration will require the development of many pieces of technology including development of monitoring tools and techniques. An underground laser based monitoring system was built and tested at Montana State University (MSU) to measure sub-surface CO2 concentrations at a sequestration site. The instrument uses differential absorption spectroscopy by temperature tuning a distributed feedback diode laser over several CO2 absorption features located at 2.004 microns. The instrument utilizes photonic bandgap fibers for sub-surface spectroscopy CO2 concentration measurements. The instrument was tested at a controlled release facility located on the MSU campus. The field and CO2 release are managed by the Zero Emissions Research and Technology group at MSU. Three CO2 injection tests were done over the coarse of two summers to simulate a fault or fracture line at a sequestration site. Results from all three tests are presented showing that the underground differential absorption instrument could be used to monitor sequestration sites.