Measurement and correlation of compressibility factor of high CO2-content natural gas

The JEFRI-PVT apparatus made in Canada by the Schlumberger company has been used to obtain accurate compressibility factor measurements on high CO2-content natural gasses so as to study the effect of different CO2 content on gas compressibility factor (range covered: temperature, 263.15 K to 313.15 K; pressure, 3 MPa to 15 MPa; CO2 content, 9.84, 28.86 and 50.99 mol%). The results showed that gas compressibility factors reduce with increasing CO2 content in natural gasses and increase with increasing temperature. In addition, a non-integral power polynomial correlation was proposed without an iterative procedure whose coefficients were determined by fitting experimental data. The mixing rules used include: Kay's mixing rule combined with Wichert-Aziz correlations (Kay) and Stewart-Burkhardt-Voo mixing rule with Wichert-Aziz (SBV). Comparison of the DAK-SBV, DAK-Kay, and proposed correlations showed that the presented model yielded the most accurate predictions with the lowest average absolute deviation (0.42%) among them.

► Compressibility factor of high CO2-content natural gas was measured by a JEFRI-PVT.
► The study was made at temperatures of 263.15~313.15 K and pressures of 3.0~15.0 MPa.
► Compressibility factor reduces with CO2 content and increases with temperature.
► The non-iterative model is the most accurate among all considered models.