Surface Monitoring Strategies at CO2 Storage Sites
Geological CO2 storage is viewed as a potentially viable strategy for reducing greenhouse gas emissions from point sources such as power plants, fertilizer production facilities and bio-ethanol fermenters, etc. However, for this strategy to be successful at its aim of reducing greenhouse gas emissions, a monitoring strategy is required to ensure that the CO2 remains in the intended storage reservoir and does not leak. Furthermore, monitoring is required in most jurisdictions around the water as a permitting condition. It is also necessary to provide assurance to the community and other stakeholders that the CO2 being stored is not affecting the environment. There are many subsurface monitoring techniques including pressure monitoring, 4D seismic, etc.; however, these must be complemented by surface monitoring approaches. Based on our experience monitoring fugitive methane emissions for the gas industry, we have found that mobile surveys using vehicles containing real-time spectroscopic analysis equipment that sample gases from the atmosphere can be used to identify potential leaks. Similarly, this approach could be used for monitoring of the nearby region surrounding a CCS storage site. However, this strategy suffers from several disadvantages such as limited land access, poor wind conditions, variation in leak rate over time and interference from other sources (e.g. agriculture, vehicles and industry) that might preclude the detection of an actual CO2 leak. Furthermore, this strategy only provides a snapshot of the leak characteristics at a particular time which may or may not be indicative of long term behavior. To complement this approach, fixed site monitoring can be utilized; however, current fixed-site monitoring approaches can be quite expensive. This can lead to a situation where a very limited number of fixed monitoring sites are implemented. Furthermore, the site selected for the fixed monitoring station may be biased or not indicative of the actual overall emissions in the field. To rectify this, a high density of low-cost and reliable sensors is required. This approach would meet regulatory requirements, provide assurance to the community and provide actionable information in the event of a substantial leak. In this paper, we will show that the combined approach of fixed-site and mobile monitoring can each address many of the disadvantages of the other.
KeywordsCCS Monitoring Sensors Greenhouse gases