A primary factor influencing long-term geologic storage of carbon dioxide is caprock integrity. Large-scale CO2 injection projects require improved and advanced simulation tools and risk assessment techniques to better predict and manage system failures. As part of this DOE-funded project we have completed a multi-phase geomechanical caprock integrity study to advance understanding of caprock integrity issues.
First, we provide a review, analysis, and description of historical leakage events related to caprock integrity within the natural gas storage industry. Second, we develop and describe analytical equations that can be applied for first order estimates of induced stresses and strains due to pressure and temperature changes related to CO2 injection. Next we describe a process for one-way coupled fluid and heat flow simulation and geomechanical simulation to estimate induced stresses and failure risks. Finally a quantitative risk and decision analysis tool to assess caprock integrity was also developed and applied.
Analysis & Conclusion
First, from our detailed review, analysis, and description of historical leakage events related to caprock integrity within the natural gas storage industry, we conclude that risks for gas leakage events are generally higher than previously estimated and published, and are in the range of 10^-1 to 10^-2. Second, coupled transport flow and geomechanical simulations of three large-scale geologic sequestration sites were completed to analyze their potential of caprock failure due to geomechanical damage. Induced stresses in each of the fields investigated are not sufficient to raise concerns regarding caprock fracturing or fault activation. Third, we have developed and documented a quantitative risk and decision analysis tool to assess caprock integrity risks. Application to five study sites indicates that the Kevin Dome site presents the least risk for CO 2 injection, while the Wilmington Graben site present the highest risk.
Final report can be found here.