A numerical simulation of a dry-out process for CO2 sequestration in heterogeneous deep saline aquifers

Salt precipitation can be generated near the injection well when dry supercritical CO2 (scCO2) is injected into deep saline aquifers. Traditional laboratory experiments and numerical simulations focus on the generation of salt precipitation and its impact on core permeability. Recent laboratory experimental studies have shown that the heterogeneity of the core and water content on the surface of the particles plays an important role in the formation of salt precipitation. The goal of this study is to investigate the effects of brine back-flow, heterogeneity, and low water content on salt precipitation. Numerical simulations were performed using core-scale and site-scale models. Simulation results showed the following: 1. Back-flow plays an important role in the salt accumulation near the well – an homogeneous laboratory experiment used with a small core may not provide a full picture of the back-flow phenomenon. 2. The continuous dry-out process reduces the water content near the injection well to zero. As a result, the full range of saturation flow equations should be used to simulate the dry-out process accurately. 3. The heterogeneity of the matrix not only affects the distribution of salt precipitation but also increases the amount of salt precipitation near the well. Homogeneous simulation underestimates the amount of salt precipitation. 4. The reduction in porosity due to salt precipitation could extend the dry-out process in the low permeability zone, further expanding the salt precipitation area. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd