Predictions of Two-Phase Critical-Flow Boundary and Mass-Flow Rate Across Chokes

Abstract

Summary The objective of this study is to develop and validate a theoretical slip model for two-phase flow through chokes. As opposed to the models (Sachdeva et al. 1986; Perkins 1993) used currently by the industry, the present model accounts for slippage between the liquid and gas phases as they pass through the choke. The theoretical basis of the model is a 1D balance equation of mass, momentum, and energy with the assumptions of constant quality and incompressible liquid phase. The present slip model is capable of predicting the critical-subcritical-flow boundary and the critical and subcritical mass-flow rates. A model-validation study demonstrated the capability of the slip models to predict the critical-flow boundary with an average error and standard deviation of 5.2% and 15.5%, respectively. Furthermore, in a laboratory validation, the present slip model predicted the mass-flow rate with an average error of 2.7% and 12.5% standard deviation. Compared with field data, the present slip model predicted the mass-flow rate with 1.4% average percent error and 15% standard deviation. Compared to existing no-slip models (Sachdeva et al. 1986; Perkins 1993) used commonly by the industry, the present slip-model predictions outperformed their predictions in the average percent error in both laboratory and field validation and in the standard deviation in the laboratory validation only. This validation result indicates the importance of the slippage phenomenon.