Development of a Novel Infrared Detector for Improved CO2 Subsurface Sequestration Monitoring

Low cost and accurate monitoring of sequestered gases such as CO2 is critical to insure that these gases are not reentering the atmosphere. Management requires, in part, improved atmospheric and ground monitoring of these greenhouse gases through sensors capable of measuring the subsurface flux, concentration and the carbon isotopologues of CO2 with high accuracy. These Monitoring, Verification and Accounting (MVA) tools needs to meet very strict requirements including; (a) the ability to differentiate between natural and anthropogenic CO2; (b) sensitive to the location of injected CO2 and any potential release; (c) robust enough for operating in harsh environments; and (d) capable of monitoring requirements across the range of storage formation(s), depth)s), temperature(s), pressure(s) and porocities. The ability to differentiate between natural and anthropogenic CO2 emissions requires detectors that can differentiate CO2 isotopologues. In this program an ultra-sensitive infrared CO2 sensor system, designed to optimally operate at 4.35 m, where both CO2 isotopologues are optically active will be constructed for MVA monitoring. The sensor will be able to accuracy and rapidly measure the concentration and isotopic ratio of CO2 isotopologues, and thus determine the gas origin. The ultra-high performance infrared CO2 sensor will be deployed and field tested at the University of Montanas Zero Emission Research Technology (ZERT) subsurface CO2 field site. In Phase I an infrared detector optimized for detection at 4.35 microns, which is ideal to detect and measure CO2 isotopologue amounts and ratios, was designed, fabricated, and tested. A methodology for incorporating this into a proven CO2 gas monitoring system at Montana State ZERT facility was also developed. The detector constructed in Phase I will be incorporated into the ZERT gas monitoring system for MVA to monitor sequestered CO2. This will upgrade the system capabilities significantly, and will be capable of discriminating between natural and anthropogenic CO2. After construction, this system will then be optimized and laboratory developed to assure optimum performance and field tested. Commercial Application and Other Benefits A low noise high sensitivity mid infrared detector for use in CO2 monitoring has been developed. This detector is being incorporated into a carbon sequestration monitor that can differentiate between naturally occurring and anthropogenic CO2 in Phase II. This technology can be translated to other applications including monitoring of other greenhouse gasses that have absorption bands in the infrared. This system could also be used to monitor other dangerous gases that have an infrared absorption signature.