SOIL CO2 FLUX MONITORING EXPERIENCES FROM A LARGE-SCALE CARBON SEQUESTRATION DEMONSTRATION PROJECT

The Illinois Basin – Decatur Project (IBDP) is a large-scale, geologic carbon sequestration demonstration project which has successfully injected 1 million metric tonnes of carbon dioxide (CO₂) in the Mt. Simon Sandstone. The IBDP project has an extensive monitoring program to evaluate subsurface and near-surface conditions before, during, and after CO₂ injection, and assess the effectiveness of a range of monitoring techniques. The IBDP soil flux monitoring program ran from 2009 to 2015, consisting of weekly point measurements at 103 to 118 locations, and a multiplexer system deployed for longer periods of time to collect higher-frequency measurements. Over 12,700 measurements were made across the point network, and over 90,000 flux measurements were collected with the multiplexer. Concurrent soil temperature and soil moisture measurements were collected whenever possible.

Overall, the monitoring network was successful in documenting the highly dynamic soil CO₂ fluxes during the project. However, data collection and analysis were challenged by: 1) equipment malfunctions during periods of extended deployment, 2) physical disturbances to the network by local industrial activities, 3) physical damage from wildlife and weather, 4) personnel turnover, and 5) the significant investment of time and resources required to establish, maintain, and measure the network.

The IBDP experience indicates that an intensive soil flux monitoring network is not viable on a commercial scale. Further, recent leak studies at the Zero Emission Research and Technology Center, Ginninderra, and Latera Caldera suggest that surface leaks are unlikely to be detected by a point flux network. While some targeted soil CO₂ flux monitoring may be useful to projects in order to establish an understanding of general soil flux conditions, soil flux monitoring may be best suited for establishing baseline information and used for field quantifications if surface leaks were present.