Process-based Method of Detection of Deep Gas Invading the Near-Surface (Groundwater and Vadose Zone)
Physical Sciences : Materials and Compounds
Available for licensing
- Katherine Romanak , University of Texas at Austin
- Philip Bennett , University of Texas at Austin
- David Bomse , MesaPhotonics
- Marwood Ediger , Mesa Photonics
Since the Industrial Revolution, carbon dioxide emissions to the atmosphere have continually increased. Several technologies have been developed and are being implemented to address these troubling increases. One such method is Carbon Capture and Storage (CCS), in which carbon dioxide (CO2) is chemically removed from power plant emissions, compressed, and stored for shipment to off-site uses. The safe and effective implementation of CCS depends on several factors, particularly the monitoring for unsuspected leaks or slow release of CO2 through porous geology.
A critical issue for geologic carbon sequestration is the ability to detect CO2 in the vadose zone. There are several drawbacks to the current comparison-based method in which new CO2 measurements are compared to a baseline sample over a one-year period. First, one year of background monitoring cannot account for the full range of natural CO2 variation that could occur over the lifetime of a CCS project. Second, if the magnitude of a leakage signal is smaller than natural variability, then the leak may be overlooked. Third, background measurements require a long lead time, potentially hindering progress on the project. Finally, CO2 cannot be measured across all potential leak points within an area of review.
A gas analyzer can also be used as part of a soil gas analysis method that can identify CO2 leaking from underground CCS sites and potentially at shale gas sites in the future. The gas analysis method requires determining the concentrations of various elements in the soil gas. Although suitable sensors are available for measuring most of these elemental gases, no such sensor is currently available for nitrogen. Gas chromatography (GC) is the current method for measuring gas concentrations in the soil gas, but requires consumable supplies such as bottled hydrogen for operating the chromatograph. GC also does not provide real-time monitoring, producing "data gaps" in analysis results. Accurate determination of nitrogen concentrations in soil gas is needed to ensure mass balance in the soil gas analyses that are used for site leak detection.
Researchers at The University of Texas at Austin have developed and demonstrated a method for single-shot analysis of CO2 concentration in soil that pinpoints the source of carbon and does not require multiple years of baseline data to determine changes over time. Relationships among major fixed gases are used to instantaneously identify processes that create and alter vadose zone CO2 concentrations. The capability for real-time continuous soil gas data collection has the potential to enhance monitoring efficiency, reliability, and defensibility to ensure the CCS project is performing as designed.
Researchers also developed instrumentation for measuring nitrogen concentrations in soil gas. The produced nitrogen measurements achieve the accuracy needed for CCS and/or shale gas leak determination on a useful timescale. The proposed invention is a replacement for GC measurements of nitrogen and can also be used simultaneously to measure oxygen concentrations. This expresses a lower cost of operation for the gas analyzers and makes implementation of leakage detection more accurate and cost-effective. The technology also facilitates real-time continuous automated site monitoring, with the potential for data telemetry which will aid in upscaling the technology to industrial scales.
- Powerful yet simple geochemical approach to leakage monitoring
- Applicable to CCS sites and potentially at shale gas production sites
- Does not require years of background monitoring, as needed by current methods
- Improved accuracy of CO2 measurements
- Cost-effective, low cost of operation
- Nitrogen monitoring simultaneously measures oxygen concentrations and operates without the need for consumable supplies
- Higher degree of assurance due to direct measurement of nitrogen
- Real-time continuous automated site monitoring eliminates "data gaps" in soil gas analysis
- New approach to detect CO2 leakages the vadose zone above CCS sites
- Separates leakage signals from natural CO2 cycling processes
- Instantaneously identifies natural CO2 cycling processes
- Facilitates real-time continuous soil gas data collection
- Employs direct measurement of nitrogen that is lacking in commercially available sensors
- Replaces GC as a method for soil gas analysis and CCS leak determination
- Nitrogen monitoring provides improvement on Raman scattering with an intensity up to a factor of 1,000 over conventional Raman implementations
- Potential for data telemetry
PR Newswire reports that the global CCS market size was 61,150 kilo tons in 2015. With the global energy demand rapidly rising, national governments are seeking to employ processes that reduce CO2 emissions. The market for CCS technology is expected to grow at a compound annual growth rate (CAGR) of 15.6% from 2016 to 2025. CCS not only reduces CO2 emissions, but supplies CO2 for other purposes that might benefit from using CO2 rather than alternative methods. Off-site uses may be for CO2 EOR as raw material in chemical manufacturing, or simply permanent storage in secure geological reservoirs.