Post-Extrapolation Method for Simulating Unsteady Multiphase Flow in Oil and Gas Transport Pipelines

Transient multiphase flow phenomena—such as cavitation, gas release, and pressure wave propagation—are critical challenges in oil and gas pipeline operations. These events, often triggered by sudden pump shutdowns or valve operations, can lead to equipment damage, production losses, and safety hazards. Accurate and stable simulation of such transients is essential for flow assurance, system design, and real-time decision-making in hydrocarbon transport networks. This study introduces a simulation framework based on the Post-Extrapolation Method (PEM), a numerical scheme developed to compute pressure and void fraction at specified time steps without requiring interpolation. PEM is applied to simulate one-dimensional, isothermal, transient multiphase flow representative of upstream and midstream oil and gas pipeline systems. Model validation is conducted against a well-established experimental benchmark involving cavitation and gas release phenomena. The results from PEM confirm its accuracy, stability, and suitability for modeling complex multiphase transients in oil and gas pipelines, offering a robust tool for engineers and operators.