Evaluation of CO₂ plume migration and storage under dip and sinusoidal structures in geologic formation

A series of numerical simulations were conducted to explore the frontal speed of the CO₂ plume and residence time in the formation preserving the dipping and sinusoidal caprock. For this purpose, we generated various permutations of 2-D numerical models where the contact boundary between the caprock and targeted formation was simplified with the idealized sinusoidal function. Three parameters such as dip, amplitude, and wavelength were chosen to analyze how the dipping and sinusoidal structure could affect the frontal speed of CO₂ plume. Subsequently, the study was expanded to understand the effect of caprock permeability and the heterogeneity preserved in the storage formation. Simulation results under the condition of dipping caprock (2°–10°) indicated that the relationship between the migration distance of the CO₂ plume front and time followed the linear trends. Among the chosen sensitivity parameters of dip, amplitude, and wavelength, the speed of the CO₂ plume front was the most sensitive to the caprock dip, but the stored CO₂ mass varied the most significantly with the amplitude. In addition, when the caprock permeability increased, certain amounts of CO₂ escaped to the caprock, resulting in a retardation of the CO₂ plume. Similarly, in the sensitivity studies of dip, wavelength, and amplitudes, more CO₂ leaked to the caprock corresponded to smaller frontal speed of CO₂ plume. Finally, the increase in permeability heterogeneity of the targeted formation decreased the sharpness of CO₂ plume front while the mean arrival time of the plume front was relatively consistent.