Phase behavior and compressibility factor of two China gas condensate samples at pressures up to 95 MPa

Constant composition expansion measurements were performed using a high pressure fluid PVT system for two gas condensate samples collected from two reservoir fields in China to determine the dew point pressures and compressibility factors at different temperatures, where the experimental pressures were up to 95 MPa. For the samples studied, the experimental results showed that the dew point pressures decrease with the increase of temperature and the gas compressibility factors increase with the increase of pressure in single phase zone at four temperatures. Thermodynamic models that combining equations of state with different kinds of plus-fraction splitting and critical properties of pseudo-components characterization methods were compared and optimized to describe the phase behavior and volumetric properties of gas condensate samples under high-pressure and high-temperature conditions. The preferred model has a better description for dew point pressures and gas compressibility factors with the total average absolute deviation for two samples of 0.64% and 1.56%, respectively.

► Constant composition expansion tests are performed under pressure up to 95 MPa. ► Dew point pressure and compressibility factor for two gas condensates are obtained. ► Thermodynamic models that combined EOS with characterization methods are compared. ► Models to describe gas condensate samples under HPHT conditions are optimized.