Study of Gas Condensation in Transmission Pipelines With a Hydrodynamic Model

Abstract

A nonisothermal, ID, compositional, two-fluid, multiphase hydrodynamic model is used to describe the incipient formation and dynamic behavior of condensate in a natural-gas pipeline with undulating topology. The 26-in. [66-cm] -diameter case-study transmission pipeline traverses 180 elevation changes in its 30. 72-mile [49.4-lan] span. Results demonstrate the predictive and descriptive potential of the model in field applications and the significant effect of inclination and inclination changes on the hydrodynamics of gas/condensate flow in transmission pipelines. The model presented can serve both predictive and design purposes. IntroductionTwo-phase flow in natural-gas transmission pipelines is common. Accurate knowledge of the pressure profile and liquid distribution as predicted with an appropriate model is necessary for optimal design and siting of compressor stations and liquid catchers along the pipeline. Therefore. it is imperative to design such pipelines with appropriate models capable of predicting and handling two-phase fluid dynamics in pipelines. Such an approach is especially critical in the design of long-distance pipelines where the interactions between the two phases, coupled with varying inclinations, can significantly affect the pressure profile along the pipeline.Various approaches have been developed to describe the fluid dynamics of two-phase flow in pipe. Most are basically empirical and/or semiempirical, lack generality, and contain predictive inadequacies. Adewumi and Bukacek! reviewed these methods in detail. More-recent attempts have used a fundamental hydrodynamic approach to describe multiphase flow in pipes. This approach has been successful in a number of cases that are well documented in the literature. Refs. 2 through 4 report other examples of the use of this approach to solve practical problems of engineering interest.In this study, a numerical simulation package for two-phase flow in pipe was developed by coupling the hydrodynamic model and the phase-behavior package. The hydrodynamic formulation is a modification of the two-fluid model. Detailed formulation of the two-fluid model that uses the basic principles of continuum mechanics coupled with the volume-averaging technique is reported elsewhere. 2 A modified Peng-Robinson 5 equation of state (EOS) is used to describe the fluid phase behavior.A detailed analysis of the basic hydrodynamic equations used in this study was presented in Ref. 4, but the effects of gravitational force in the momentum equations are not included because that study was intended for horizontal pipelines. Several features distinguish the behavior of inclined transmission lines from that of horizontal pipes. In inclined pipeline, the effect of gravitational force must be taken into account in the hydrodynamic formulation, even for a very small inclination, because the gravitational force significantly affects the liquid velocity, the pressure gradient, and invariably the liquid holdup. Sharp changes in liquid velocity may occur several times in a pipe...

Network modelling and prediction of retrograde gas behaviour in natural gas pipeline systems

“…The results from them demonstrated the predictive and descriptive potential of the model in field applications. Mucharam et al (1990) improved the model for natural gas pipelines with undulating topology and demonstrated the significant effect of inclination and inclination changes on the hydrodynamics of gas/condensate flow in transmission pipelines. At the same time, Vincent (1990) also developed a predictive compositional hydrodynamic model with a two-parameter equation of state.…”

Gas-Liquid Stratified Flow in Pipeline with Phase Change

“…The condensation will decrease the effective cross-sectional area and cause the increase of pressure drop which may lead to system shutdown [11,16]. Generally, the condensed water accumulates at the lower parts of the pipeline due to the hilly pipeline route topography, which results in a continuous change of liquid holdup along the pipeline [12][13][14]. The changing liquid holdup and flow area are bounded to affect the flow patterns which inevitably influence the operating pressure and temperature inversely.…”

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

“…These thermo/hydrodynamic models have sought to address an operational problem while seeking a fundamental understanding of two-phase (gas/ condensate) flow in pipes. The work is well documented in the literature and needs not be repeated here Mucharam et al 1990;Ayala and Adewumi 2003).…”