The gas-liquid-liquid three-phase co-current flow is frequently observed in upstream petroleum pipelines. The identification of three-phase flow patterns is important to characterize three-phase flow dynamics. The three-phase flow patterns change with the pipe diameter, superficial velocities and physical properties of the fluids. Computational fluid dynamics (CFD) analysis of three-phase flow through 0.1524 m diameter and 3.5 m long horizontal pipe has been conducted. The superficial velocity ranges of gas-oil-water were 0.5-4, 0.08-0.32 and 0.08-0.32 m/s respectively. The volume of fluid (VOF) model was used to simulate the three-phase interfacial structures. According to the results, the three-phase flow patterns have been successfully simulated. Three-phase flow regime map has been constructed to analyze the flow pattern transition with the superficial velocities. The three-phase flow pressure drop increased with the superficial velocities of oil and water. However, the drop in pressure first increased and then decreased with the increase in superficial velocity of the gas. © Published under licence by IOP Publishing Ltd.