Design of a perfluorocarbon tracer based monitoring network to support monitoring verification and accounting of sequestered CO₂

Brookhaven Science Associates, PO Box 5000, Upton, NY 11973-5000, USA

Abstract

The levels of CO₂ in the atmosphere have been growing since the beginning of the industrial revolution. The current level is 391 ppm. If there are no efforts to mitigate CO₂ emissions, the levels will rise to 750 ppm by 2100. Geologic carbon sequestration is one strategy that may be used to begin to reduce emissions. Sequestration will not be effective unless reservoir leak rates are significantly less than 1%. There must be rigorous monitoring protocols in place to ensure sequestration projects meet regulatory and environmental goals. Monitoring for CO₂ leakage directly is difficult because of the large background levels and variability of CO₂ in the atmosphere. Using tracers to tag the sequestered CO₂ can mitigate some of the difficulties of direct measurement but a tracer monitoring network and the levels of tagging need to be carefully designed. Simple diffusion and dispersion models are used to predict the surface and atmospheric concentrations that would be seen by a network monitoring a sequestration site. Levels of tracer necessary to detect leaks from 0.01 to 1% are presented and suggestions for effective monitoring and protection of global tracer utility are presented.