Investigation of the Effects of Unconformity Surface on Geological Storage of CO2

CO2 has lower density than brine and is a buoyant fluid. Therefore, after injecting CO2 into saline aquifers, CO2 will move upward under buoyancy to reach a barrier. Afterward CO2 will spread underneath and moves laterally which depends on the caprock and aquifer interface. One type of interface is unconformity surface. In this work, the effect of this interface on CO2 dissolution was investigated by conducting 2D numerical simulations and it is concluded that in low injection scenarios, distance travelled by CO2 plays a significant role to increase CO2 dissolution. In addition, existence of high permeable layer at unconformity surface which was formed due to erosion or deposition of large grain sediments increases CO2 dissolution by providing additional pathways to other storage formations. In higher injection rates however, both pressure build up and distance traveled by CO2 play role. In absence of the high permeable layer, pressure in the formation increases and this triggers more CO2 dissolution. Overall, precisely choosing well or perforation location and injection rates will increase the CO2 dissolution as a long term trapping mechanism and will reduce the potential for leakage. In addition, sensitivity of CO2 dissolution to temperature and salinity gradients was examined.