Dependence on temperature and salinity gradients and the injection rate of CO2 storage in saline aquifers with an angular unconformity

One type of interface between an aquifer and the caprock is an unconformity surface. The term refers to a buried erosional or non-depositional surface separating two strata of different age, indicating that sediment deposition was not continuous. Just above or below the unconformity surface, a high or low-permeability layer may exist. The high-permeability layer could be the result of weathering and erosion of the older layer or deposition of the coarse-grained sediments on top of the unconformity surface. The effect of this interface on CO2 dissolution in brine is investigated by running a range of 2D models and considering different injection scenarios. By examining different injection scenarios, when 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-permeable layer creates a pathway for the further migration of CO2, in almost all injection scenarios, the models without a high-permeable layer have tended to predict a higher CO2 dissolution. In addition, the sensitivity of CO2 dissolution to aquifer parameters, such as temperature and salinity gradients, is examined. Models with and without temperature and salinity gradients are compared and the importance of these parameters on the prediction of CO2 storage is 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.