Abstract:

TOUGH2/ECO2N code was used to simulate the complex coupled processes taking place during and after CO₂ injection in the deep saline sandstone aquifer of Lower Yancheng Formation in Subei basin. Morris, Sobol and EFAST methods were used to analyze the global sensitivity of parameters, i.e., k_x, n, S_lr,λ, C, 1/p₀ and S, on three response variables: 1)the pressure located in the injection well; 2)the amount of gas-phase CO₂ and 3)the spread distance of CO₂ gas plume. Results from the Morris and Sobol methods show that n is the most sensitive parameter for the injection well pressure, k_x is the most sensitive parameter both for the amount of gas-phase CO₂ and the spread distance of CO₂ gas plume. In summary, the sensitivity orders of these parameters are totally different for different corresponding variables. Comparative results from EFAST and Sobol show that the main and total effect obtained from the two quantitative sensitivity analysis methods are basically identical, however, EFAST is computationally more efficient than Sobol in numerical experiment.

Key words: CO₂ geological sequestration, global sensitivity analysis, Morris, Sobol, EFAST, Subei basin