Influences of temperature and pressure on CO2 solubility in saline solutions in simulated oil and gas well environments

The phase equilibria of H2O-CO2-NaCl systems is of general interest to many scientific disciplines and technical fields. One aspect is the CO2-mediated corrosion of oil country tubular goods in deep saline aquifers. In this study, CO2 solubility experiments were conducted in simulated oil and gas well environments using a novel experimental apparatus and method. The solubility of CO2 in deionised water and NaCl solutions was measured at temperatures of 303.15-363.15 K and pressures of 50-250 bar. The impacts of temperature, pressure and salinity on CO2 solubility are analysed quantitatively and qualitatively and are consistent with published data. CO2 solubility increases with pressure in all cases, and pressure inhibits the effect of temperature on CO2 solubility to some extent. An interesting phenomenon is that CO2 solubility increases with pressure much faster at low pressures than at high ones. A transition pressure of 150 bar was determined at medium-low temperature and low salinity.