6.4.1 Weyburn, Canada

At Weyburn (Canada), the long-term behavior of the CO2 and leakage risks at were assessed within a methodological framework based on the FEPs (Stenhouse et al., 2005). The Quintessa FEP database was initially developed for this application. A number of simulations were performed. Fully probabilistic calculations find a 95% probability that the cumulative amount of CO2 released after 5,000 years will be less than 1% of the total amount stored (Walton et al., 2004). A deterministic model for transport in the reservoir with probabilistic model for leakage through wells shows a maximum release of 0.14% of the total amount of CO2 stored (Zhou et al., 2004). The Weyburn risk analysis indicated that the most probable path for transmission of CO2 from one stratum to another or to the biosphere is along a well bore. Therefore, wells must be carefully drilled and monitored. Application of the CQ-1 program based on simulations showed that CO2 may migrate from the initial formation tending to dissolve in the aquifers above the reservoir. Based on the Monte Carlo simulation method, after 5,000 years, the mean release to the biosphere of CO2 in place will be 0.2%. 5-34% of CO2 initially in place in the Weyburn formation will migrate to upper and lower aquifers. There is 95% probability that 98.7-99.5% of the initial CO2 in place will remain stored in the geosphere for 5,000 years (Deel et al., 2007).