Feras Al-RuhaimaniEduardo PereyraCem SaricaEissa Al‐SafranCarlos Torres2026-03-222026-03-22201610.2118/184401-pahttps://doi.org/10.2118/184401-pahttps://andeanlibrary.org/handle/123456789/43777Citaciones: 34Summary Understanding the behavior of two-phase flow is a key parameter for a proper oil/gas-production-system design. Mechanistic models have been developed and tuned to model the entire production system. Most existing two-phase-flow models are derived from experimental data with low-viscosity liquids (μL < 20 mPa·s). However, behavior of two-phase flow is expected to be significantly different for high-viscosity oil. The effect of high liquid viscosity on two-phase flow is still not well-studied in vertical pipes. In this study, the effect of high oil viscosity on upward two-phase gas/oil-flow behavior in vertical pipes was studied experimentally and theoretically. A total of 149 air/high-viscosity-oil and 21 air/water experiments were conducted in a vertical pipe with an inner diameter (ID) of 50.8 mm. Six different oil viscosities—586, 401, 287, 213, 162, and 127 mPa·s—were considered. The superficial-liquid and -gas velocities were varied from 0.05 to 0.7 m/s and from 0.5 to 5 m/s, respectively. Flow pattern, pressure gradient, and average liquid holdup were measured and analyzed in this study. The experimental results were used to evaluate different flow-pattern maps, mechanistic models, and correlations for two-phase flow. Significant discrepancies between experimental and predicted results for pressure gradient were observed.enViscosityFlow (mathematics)Two-phase flowMechanicsMaterials sciencePhase (matter)Pressure gradientVolumetric flow rateThermodynamicsPetroleum engineeringarticle