Vol 2 Chapter 20: Atmospheric CO2 Monitoring Systems
Patrick Shuler and Yongchun Tang
Abstract: Monitoring for atmospheric CO2 concentrations may be an integral part of any subsurface storage project. Several CO2 measurement methods may be used to meet the monitoring objectives of:
- assuring there are no large leaks at the surface that might pose a health risk and
- verifying that the injected CO2 remains trapped below the Earth’s surface.
- remote sensing from satellites or aircraft,
- open path instruments that can sample over significant distances and
- a network of conventional fixed-point detectors.
NASA indicates satellite surveys might be useful for a “global” view of CO2. Aircraft surveys may be a fast means to collect data near ground level, but this is only practical in an infrequent basis. Instruments located near ground level that are based on open path sampling may offer the most efficient means to monitor long term over a large surface area. They could have the capability to detect increases of just a few percent of CO2 above normal background, over a sample path of tens of meters, and continuously with unattended operation. Many different commercial fixed-point units based on infrared (IR) spectroscopy are available. These detectors may be better suited to monitor sensitive, high-risk points of leakage rather than be deployed in a network to monitor large surface areas. Besides reviewing atmospheric monitoring options, this chapter also quantifies the capability of groundlevel instruments to identify leakages of carbon dioxide from the subsurface. In particular, the objective is to successfully detect the uniform leakage of as little as 1% of the total carbon dioxide injected into the subsurface over 100 years. This analysis suggests the local increased concentration of carbon dioxide into the atmosphere due to such a leak depends greatly on the leakage area, time duration, atmospheric conditions and proximity of the detector to the leak. In some scenarios such a leak would cause an increase of at least tens of ppmv of carbon dioxide in the near-surface atmosphere and likely would be detected by commercially available instruments as being above the natural background variations of carbon dioxide.
Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO2 Capture
Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA
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