A Multiscale Mechanistic Model for Slow Transient Two-Phase Gas Condensate Flows in Pipelines

Various technical, commercial and operational requirements and conditions warrant the modelling of gas condensate pipelines as two-phase flows. Although phenomenological descriptions of two-phase flows are commonly used in the Oil and Gas Industry, the thermal-hydraulic complexities of such systems mean that a number of mechanistic formulations are available, some emphasising accuracy at the expense of computational efficiency, others preferring a more simplified approach. This article proposes a fully mechanistic slow transient model of two-phase condensate gas flows in pipelines, where the slip relation is derived from first principles using a mutliscale expansion method. Representative steady state and transient case studies for different operational conditions are simulated and solved numerically. Results are analysed and validated against an industry standard Two-Fluid Model based software.