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Pre-site Characterization Risk Analysis for Commercial-Scale Carbon Sequestration

Dai, Zhenxue, Stauffer, Philip H., Carey, J. William, Middleton, Richard S., Lu, Zhiming, Jacobs, John F., Hnottavange-Telleen, Ken, Spangler, Lee H.
Environmental Science & Technology 2014 v.48 no.7 pp. 3908-3915
Monte Carlo method, carbon dioxide, carbon sequestration, monitoring, risk, risk analysis, rocks, wells, Montana
This study develops a probability framework to evaluate subsurface risks associated with commercial-scale carbon sequestration in the Kevin Dome, Montana. Limited knowledge of the spatial distribution of physical attributes of the storage reservoir and the confining rocks in the area requires using regional data to estimate project risks during the pre-site characterization analysis. A set of integrated Monte Carlo simulations are used to assess four risk proxies: the CO₂ injectivity, area of review (AoR), migration rate into confining rocks, and a monitoring strategy prior to detailed site characterization. Results show a reasonable likelihood of reaching the project goal of injecting 1 Mt in 4 years with a single injection well (>58%), increasing to >70% if the project is allowed to run for 5 years. The mean radius of the AoR, based on a 0.1 MPa pressure change, is around 4.8 km. No leakage of CO₂ through the confining units is seen in any simulations. The computed CO₂ detection probability suggests that the monitoring wells should be located at less than 1.2 km away from the injection well so that CO₂ is likely to be detected within the time frame of the project. The scientific results of this study will be used to inform the detailed site characterization process and to provide more insight for understanding operational and technical risks before injecting CO₂.