Abstract

MARIN, Flavio  and  PEREZ, Narciso. Prediction of phase equilibrium in natural gas well tubing using cubic equations of state. Rev. Fac. Ing. UCV [online]. 2011, vol.26, n.4, pp.101-109. ISSN 0798-4065.

This work arises from the need to estimate the condensate profile of a natural gas well tubing, as part of the development of a commercial simulation package, that employs the thermodynamic models proposed by Soave, Peng-Robinson and Kabaddi-Danner to estimate the condensate and condensed water formation in natural gas well tubing was studied. A calculation algorithm to estimate the condensate profile using tubing segments was designed using the Phi-Phi equilibrium model. The study included the development of the mass balance equations for vapor-liquid equilibrium (VL) and vapor-liquid-liquid equilibrium (VLL), and the use of cubic equations of state to determine the fugacity coefficients and the equilibrium constant of each substance; the Wilson equation was used to determine the initial values of the equilibrium constants. The obtained results using each cubic equation were compared with field data, it was determined that the error in the condensate estimation was less than 20% for vapor-liquid equilibrium and less than 6% for vapor-liquid-liquid equilibrium. The estimated error for the difference between the results obtained by each equation of state was less than 7%. The Kabaddi-Danner equation of state and the model of three-phase equilibrium represent with high reliability the phase equilibrium of single-chain hydrocarbons and water systems.

Keywords : Equations of state; Phase equilibrium; Tubing; Gas well; Natural gas; Condensate.

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