M g = gas molecular weight = 28.967 γ gįor the data from which the correlation was developed, the standard deviation in the calculated gas viscosity was 2.7%, and the maximum deviation was 9%.are for specific units as noted below and are as follows: The method uses the gas temperature, pressure, z factor, and molecular weight, which have to be measured or calculated the density can be measured or calculated as well. This method lends itself for use in computer programs and spreadsheets. developed a useful analytical method that gives a good estimate of gas viscosity for most natural gases. 5 – Pseudocritical properties of methane-based natural gases (from Sutton ). 2 are corrections to be added to the atmospheric viscosity when the gas contains N 2, CO 2, and H 2S.įig. If only specific gravity is known, then the pseudocritical properties would have to be obtained from Fig. However, Kay’s rules require a full gas composition. to calculate the pseudocritical properties for use with those charts. It would not be correct, then, to use the methods of Sutton or Piper et al. ) are based on pseudocritical properties determined with Kay’s rules. 4) to obtain the viscosity at reservoir temperature and pressure. This viscosity is then multiplied by the viscosity ratio (from Fig. N = number of components in the gas mixture.M gi = molecular weight of the ith component of the gas mixture.μ i = viscosity of the ith component of the gas mixture at the desired temperature and atmospheric pressure (obtained from Fig.y i = mole fraction of the ith component.μ ga = viscosity of the gas mixture at the desired temperature and atmospheric pressure.2 or determined from the gas-mixture composition with Eq. The viscosity of gas mixtures at one atmosphere and reservoir temperature can either be read from Fig. 4 – Effect of temperature and pressure on viscosity of natural gases (from Carr et al.
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