An improved strategy to detect CO2 leakage for verification of geologic carbon sequestration

The long‐term storage of CO2 must be verified to ensure the success of geologic carbon sequestration projects. To detect subtle CO2 leakage signals, we present a strategy that integrates near‐surface measurements of CO2 fluxes or concentrations with an algorithm that enhances temporally‐ and spatially‐correlated leakage signals while suppressing random background noise. We assess the performance of this strategy using synthetic CO2 flux data sets and modeled surface CO2 leakage. These simulations provide a means of estimating the number of measurements required to detect a potential CO2 leakage signal of given magnitude and area. Results show that given a rigorous and well‐planned field sampling program, subtle surface CO2 leakage may be detected using the algorithm; however, leakage of very limited spatial extent or exceedingly small magnitude may be difficult to detect with a reasonable set of monitoring resources.