Solubility of CO₂ in aqueous solutions of CaCl₂ or MgCl₂ and in a synthetic formation brine at temperatures up to 423 K and pressures up to 40 MPa

We report the solubility of carbon dioxide in CaCl2(aq) and MgCl2(aq) at molalities of (1, 3, and 5) mol·kg–1, temperatures of (308 to 424) K and pressures up to 40 MPa. We also report the solubility of CO2 in a synthetic formation brine containing 0.910 mol·kg–1 NaCl and 0.143 mol·kg–1 KCl over the same ranges of temperature and pressure. The expanded uncertainties at 95 % confidence are 0.03 K in temperature, between (0.08 and 0.15) MPa in bubble pressure and 0.00015 in the mole fraction of CO2 in the solution at its bubble point. The results show a strong salting-out effect, whereby the solubility declines with increasing molality of salt, which is some (20 to 30) % greater in CaCl2(aq) or MgCl2(aq) than in the synthetic formation brine at the same molality.