Prediction of CO2 solubility in NaCl brine under geological conditions with an improved binary interaction parameter in the Søreide-Whitson model

Abstract

The accurate prediction the CO2 solubility in the aqueous NaCl solution under geological conditions is essential in CO2 geo-energy resources recovery and CO2 geological storage practices, therefore has attracted extensive academic interests. In this paper, comprehensive thermodynamical calculations are performed concerning the CO2 solubility in aqueous solutions with various sodium chloride concentrations of 1–6 m (mol/kgw) at the geological pressure and temperature conditions of 313–433 K and 0.5–30 MPa. A new binary interaction parameter (BIP) in Søreide-Whitson (SW) model is proposed to improve the calculation accuracy in the wide salinity, temperature and pressure ranges. Through systematic comparisons with the 42 experimental sets and 206 measurement points on the solubility of CO2 in NaCl brine, the employed thermodynamic model as well as the modeling results is well validated based on the satisfactory Average Absolute Deviation (AAD) value of 3.77%. At last, detailed analysis on effects of salinity, temperature and pressure are carried out based on the calculation results. It is found the solubility of CO2 decreases with increasing salinity and decreasing pressure. There are oversteps for the CO2 solubility under different temperatures when the system pressure is higher than 20 MPa.