An unconformity surface is a type of interface between an aquifer and a caprock. It refers to a buried erosional or non-depositional surface that separates two strata of different ages, indicating that sediment deposition has not been continuous. A high- or low-permeability layer may exist just above or below the unconformity surface. The high-permeability layer could be the result of the weathering and erosion of the older layer, or the deposition of coarse-grained sediments on top of the unconformity surface. The effect of this interface on CO2 dissolution in brine was investigated by running a range of 2D models and considering different injection scenarios. By examining different injection scenarios using two models for comparative analysis (one with and one without a high-permeability layer), the results provide a good hypothesis of the effects of pressure and migration distance on CO2 dissolution. Although the high- permeability layer creates a pathway for the further migration of CO2, the models without a high- permeability layer have tended to predict a higher CO2 dissolution in almost all the injection scenarios. In addition, the sensitivity of CO2 dissolution to aquifer parameters, such as temperature and salinity gradients, was examined. Models with and without temperature and salinity gradients were compared, and the importance of these parameters on the prediction of CO2 storage was determined. Another significant result is that under higher injection scenarios, the models show significant sensitivity to temperature and salinity gradients. However, for lower injection rates the sensitivity of the dissolved CO2 to temperature and salinity gradients is almost negligible.
