Using subsurface CO2 concentrations and isotopologues to identify CO2 seepage from CCS/CO2-EOR sites: A signal-to-noise based analysis

► A signal-to-noise ratio (SNR) based approach to evaluating the effectiveness of surface based monitoring techniques is developed. ► This SNR approach is applied to the commonly used method of subsurface bulk CO2 and isotopic measurements. ► SNR provides an excellent metric for evaluation of the effectiveness of a monitoring approach. ► Other factors such as desired signal and site heterogeneity should also be evaluated when designing an efficient monitoring strategy.