Global Sensitivity Analysis to Assess Salt Precipitation for CO 2 Geological Storage in Deep Saline Aquifers

Abstract

Salt precipitation is generated near the injection well when dry supercritical carbon dioxide (scCO 2) is injected into saline aquifers, and it can seriously impair the CO 2 injectivity of the well. We used solid saturation (Ss) to map CO 2 injectivity. Ss was used as the response variable for the sensitivity analysis, and the input variables included the CO 2 injection rate (QCO2), salinity of the aquifer (XNaCl), empirical parameter m, air entry pressure (P0), maximum capillary pressure (Pmax), and liquid residual saturation (Splr and Sclr). Global sensitivity analysis methods, namely, the Morris method and Sobol method, were used. A significant increase in Ss was observed near the injection well, and the results of the two methods were similar: XNaCl had the greatest effect on Ss; the effect of P0 and Pmax on Ss was negligible. On the other hand, with these two methods, QCO2 had various effects on Ss: QCO2 had a large effect on Ss in the Morris method, but it had little effect on Ss in the Sobol method. We also found that a low QCO2 had a profound effect on Ss but that a high QCO2 had almost no effect on the Ss value.