Modelling the viscosity of natural gas mixtures

摘要

One major problem with offshore production is the difficulty in regular field sampling of various physical properties of the multiphase gas mixtures essential to process operations. Viscosity is one such important property required from simulation of gas production at reservoir conditions to the design and operations of flow lines. Thus, the development of accurate semi-empirical viscosity model is imperative to meet the increasing demand for reliable and accurate data for offshore operations. In this study, a simple correlation is presented based on modified Roelands et al equation to predict the viscosity of natural gas mixtures at temperatures between -173.15℃ and 354.02℃, and pressures from 0.1 to 14MPa. The model was developed with 40 data points from natural gas and 263 data points from C_2 and C_4 gases. The results were compared with four widely used viscosity models in the petroleum industry. The viscosity model requires only one viscosity value at 25℃ to make accurate predictions at any temperature and pressure, and gave absolute average deviations of 0.4% and 1.5% for the predictions respectively on effects of temperature and pressure on gas viscosity.