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

Highlights: • Test equipment and method of CO₂ solubility in wellbore environments are presented. • Tests of CO₂ solubility in three solutions are conducted at 303.15–363.15 K and 50–250 bar. • Correlations between CO₂ solubility and factors (T-PNaCl) are obtained. The phase equilibria of H₂OCO₂NaCl 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.