DENSITY OF HIGH PRESSURE AND TEMPERATURE GAS RESERVOIRS: EFFECT OF NON HYDROCARBON CONTAMINANTS ON DENSITY OF NATURAL GAS MIXTURES

New experimental density data are generated in this study for light and heavy dry gas mixtures. The light mixtures are consisted mostly of methane and small fractions of ethane, propane, and nitrogen or carbon dioxide. Normal alkanes up to C6, iso‑butane and iso‑pentane together with nitrogen or carbon dioxide form the heavier gas mixtures. For each mixture, isothermal gas density is measured from 3.45 MPa to 137 MPa at temperatures of 423.15 K and 473.15 K. Effect of CO2 as a non‑hydrocarbon contaminant on density of gas mixtures is examined in steps of 5 mol%, 10 mol%, and 20 mol%. In addition, water vapor influence on gas phase density of water‑saturated gas mixtures is also investigated. Different correlations for sweet and sour gas critical properties are combined with the most widely used equations of state (Hall‑Yarborough, Dranchuk et al., and Dranchuk‑Abou‑Kassem) to predict 450 measured density data. The most important results demonstrated from this study are: Among all correlations, the combination of Dranchuk‑Abou‑Kassem equation (improved by Londono et al.) with the critical properties correlated by Sutton generates the lowest average absolute deviation (AAD) between predicted and experimental density data. The correction term developed by Wichert and Aziz to modify the critical properties due to the presence of non‑hydrocarbon compounds in the gas mixture, drastically improves the prediction of density data. At very high pressure and temperature conditions, effect of water vapor becomes more considerable on gas phase density and it should be considered in density related correlations. The influence of water vapor on density of saturated gas mixtures becomes more significant as CO2 concentration increases in the mixture.