Modeling Geologic Storage of Carbon Dioxide: Effects of Low-permeability Layer on Migration of CO₂

Abstract

TOUGH2 was used to simulate the migration of CO 2 injected into a sandy aquifer. A series of numerical simulations was performed to investigate the effects of a low-permeability layer (LPL) embedded in the aquifer on the injection rate and the pressure distribution of CO 2 . The results show that the size and location of the LPL greatly affected the spread of CO 2 . The pressure difference between two points in the aquifer, one each below and above the LPL, increased as the size of the LPL increased, showing a critical value at 200 m, above which the size effect was diminished. The location of the LPL with respect to the injection well also affected the migration of CO 2 . When the injection well was at the center of the LPL, the injection rate of CO 2 decreased by 5.0% compared to the case with no LPL. However, when the injection well was at the edge of the LPL, the injection rate was decreased by only 1.6%. The vertical distance between the injection point and the LPL also affected the injection rate. The closer the LPL was to the injection point, the lower the injection rate was, by up to 8.3%. Conclusively, in planning geologic storage of CO 2 , the optimal location of the injection well should be determined considering the distribution of the LPL in the aquifer.