Modeling of multiphase flow through chokes

The accurate measurement of mass flow rate is of vital importance with respect to production control in gas or oil fields equipped with chokes. A theoretical model to predict the flow regime and mass flow rate of multiphase flow through chokes was developed and derived on the basis of Perkins and Al-safran models. In the present model, the assumption of adiabatic condition between gas and liquid was adopted alternatively when fluids flow through the throat of chokes, which is different from the existing models. The slippage phenomena between gas and liquid have also been taken into consideration in this model. After analyzing, the Schuller slip model was found to be the most appropriate one, which is consistent with the work of Al-safran. Furthermore, the effect of the discharge coefficient Cd on the model calculation accuracy was discussed. The way to calibrate irreversible loss using the optimal discharge coefficient was recommended instead of a constant coefficient, which means that experiment should be carried out for a particular choke before use. Meanwhile, the present model was validated and compared with the models currently used in fields against both subcritical and critical experimental data. The model evaluation demonstrated that the present model was more reliable in predicting the critical pressure ratio yc, especially in large GLR condition. Meanwhile, the statistical error analysis of calculated mass flow rate showed that the average percent error (E1), absolute average error (E2) and standard deviation (E3) were 0.117%, 8.754% and 0.729% for the present model, respectively. Compared to other models, the present model prediction outperforms their predictions a lot. It indicated that the present model was more reasonable and reliable in predicting the mass flow rate of multiphase flow through chokes.