Compositional Modeling of Two-Phase (Gas/Water) Flow in Pipes

Abstract

Summary The current work presents a fully compositional tool for modeling systems exhibiting two-phase (gas/water) flow. The tool couples complex hydrodynamic and thermodynamic models to describe the behavior of fluids flowing in a pipe. The model described herein focuses on gas transmission with low-liquid loading conditions (hl/d < 0.3). Results show the model is capable of predicting the hydrodynamic behavior as well as the compositional profiles of gas and water flowing in a pipe. This is important in the light of compositional dependence of hydrate or acid formation. Compositional changes in the aqueous phase may create the conditions for forming hydrates or acids. The model was benchmarked using several published works, details of which can be found in the work of Zaghloul (2006). In this paper, model performance is illustrated using a case study. The case study compares model calculations with an experimental data set obtained from Eaton et al. (1967). Model calculations predicted the observed flow pattern, pressure and liquid holdup profiles reported in the case study. Calculated pressures are within 2% of experimental values, while liquid holdup (approx 4%) is in agreement with the value predicted by Eaton's correlation (Eaton et al. 1967). The model is capable of predicting the initial water condensation point in the pipeline and the concentration of different substances in the aqueous mixture. The tool gives production engineers important information on how much hydrate/corrosion inhibitors to inject and where, thus saving in the design, operation, and maintenance of pipeline systems.