Pseudocomponent delumping for multiphase systems with waxy solid phase precipitation
Résumé
Modeling of wax precipitation from hydrocarbon mixtures requires extended compositional data for the heavy fractions; as a result, the number of components in the mixture is usually large and phase equilibrium calculations are computationally expensive and may be prohibitive. A lumping procedure which reduces the dimensionality of phase equilibrium calculations without affecting the location of solid phase transitions is used. By lumping into pseudocomponents, some information on mixture behavior is lost; this information is recovered by a delumping (inverse lumping) procedure. Delumping acts as an interface between simulation tools and results involving different fluid representation levels. The key in the delumping procedure is to relate equilibrium constants of the detailed fluid to some quantities evaluated from lumped fluid flash results. A general form of a two-parameter cubic equations of state is used for vapor and liquid phases, and heavy components are assumed to precipitate in a single solid solution. The proposed lumping/delumping procedures are successfully tested for two synthetic mixtures and a typical reservoir fluid (gas-condensate). Very good agreement is obtained between phase distributions and component mole fractions of detailed and delumped systems. This is the first time that a delumping procedure is proposed for multiphase systems with solid phase precipitation.