CO2 solubility in formation water under sequestration conditions

A high pressure experimental setup was used to measure the solubility of CO2 in an aqueous solution of different salts (salinity: ∼80000 ppm) at temperatures from (300–424) K and pressures up to 41 MPa. To ensure the validity of the experimental results and procedures, CO2 solubilities in deionised water were measured at the same pressure and temperature conditions. For both cases, experimental results were compared against predictions of the simplified cubic plus association equation of state (sCPA-EoS) [1] and Duan model [2]. Furthermore, the measured solubilities in deionised water were compared with literature experimental data.

The average absolute deviation (%AAD) of all the measured solubilities in the mixed salts aqueous solution in comparison with predictions of the sCPA-EoS and Duan model were found to be 6.88% and 4.04%, respectively. A similar comparison was also performed for the measured CO2 solubilities in deionised water. The average absolute deviation between experimental results and predictions of the sCPA-EoS and Duan model were calculated to be 7.74% and 4.19%, respectively. The percentage average expanded uncertainty (with 95% level of confidence, k = 2) for measurements conducted in deionised water and mixed salt aqueous solution were found to be 1.20% and 1.57%, respectively.