An integrated single-phase/two-phase hydrodynamic model for predicting the fluid flow behavior of gas condensate in pipelines

Current models developed for fluid flow in pipes are structured for either single-phase or two-phase flow. In fact, fluid flowing in pipelines may traverse the fluid phase envelope such that the fluid phase changes from single-phase to two-phase or vice versa. Unfortunately, the phase of the flowing fluid in pipe is unknown a priori, and available models do not integrate the single-phase flow and two-phase flow models. The development of an integrated single/two-phase flow model is the primary objective of this study. The work focuses on the development of a model that is capable of handling phase-transition. For two-phase flow, the model incorporates flow regime predictions. As this work is intended for gas-condensate with gas as the bulk of the flowing medium, only three types of flow regimes that are most likely to occur are included. These are: smooth-stratified, wavy-stratified, and dispersed liquid or mist flow regime. The model couples a phase behavior model, based on the Peng-Robinson equation of state, and a hydrodynamic model, based on the two-fluid model. Some correlations for calculating fluid properties and criteria for flow regime transition are adopted. The resulting model allows one to predict the flow behavior of a natural gas condensate system. Comparisons of the results to the limited field data demonstrate the capability of the model in describing the effects of flow parameters on condensate behavior in pipelines.