Evaluating variable switching and flash methods in modeling carbon sequestration in deep geologic formations using PFLOTRAN

PFLOTRAN a massively parallel computer code for modeling coupled hydro-thermalchemical processes in variably saturated, non-isothermal porous media is applied to sequestration of supercritical CO2 in deep geologic formations. Two different methods of solution to the governing partial differential equations are implemented referred to as variable switching and the flash approach. Variable switching entails choosing the independent variables according to the set of phases present in a control volume, whereas in the flash approach a persistent set of variables are used through the calculation. The features and performance of the two approaches are described and contrasted in regard to stability and convergence, flexibility of choice of solver, and scaling behavior.