PNNL

Abstract

The National Risk Assessment Partnership (NRAP) has developed a suite of tools to assess and manage risk at CO2 sequestration sites (1). The NRAP tool suite includes the Aquifer Impact Model (AIM), based on reduced order models developed using site-specific data from two aquifers (alluvium and carbonate). The models accept aquifer parameters as a range of variable inputs so they may have more broad applicability. Guidelines have been developed for determining the aquifer types for which the ROMs should be applicable. This paper considers the applicability of the aquifer models in AIM to predicting the impact of CO2 or Brine leakage were it to occur at the Illinois Basin Decatur Project (IBDP). Based on the results of the sensitivity analysis, the hydraulic parameters and leakage source term magnitude are more sensitive than clay fraction or cation exchange capacity. Sand permeability was the only hydraulic parameter measured at the IBDP site. More information on the other hydraulic parameters, such as sand fraction and sand/clay correlation lengths, could reduce uncertainty in risk estimates. Some non-adjustable parameters, such as the initial pH and TDS and the pH no-impact threshold, are significantly different for the ROM than for the observations at the IBDP site. The reduced order model could be made more useful to a wider range of sites if the initial conditions and no-impact threshold values were adjustable parameters.