Paper No. 13
Presentation Time: 9:00 AM-6:30 PM
USING SOIL CO2 CONCENTRATION GRADIENTS TO IDENTIFY CCS RESERVOIR LEAKAGE
Among the primary concerns associated with carbon capture and sequestration (CCS) is reservoir leakage, resulting in atmospheric CO2 release. This necessitates reliable monitoring strategies at injection sites to verify successful trapping and storage, and thereby ensure the effectiveness of the operation. Traditional surface-based leakage monitoring strategies rely on discrete measurements of soil CO2 flux utilizing chamber-based methods. Here, we develop a concentration-based monitoring technique by directly measuring the shallow soil CO2 concentration gradient during a small-scale injection experiment in DeKalb, IL. The experimental setup included 8 pairs of sample ports (5- and 9-inches deep) connected to a 16-port manifold feeding a Los Gatos Research Ultraportable Greenhouse Gas Analyzer. Using this setup, we measured the background soil CO2 concentration gradient continuously at 30-minute intervals for approximately two weeks. After obtaining the background data, we simulated a leaking CCS reservoir by injecting a small quantity of food grade CO2 into a shallow piezometer while continuing CO2 concentration monitoring for two additional weeks. By comparing the experimental data against discrete measurements of soil CO2 flux obtained by periodic sampling with a closed-chamber, we demonstrate that the concentration-based technique is an effective alternative to traditional surface flux monitoring.