In the oil and gas industry, multiphase flow environments are frequently encountered during the production and transportation of hydrocarbon products via pipelines. Most oil production wells naturally contain some fraction of water and gases. These fluids often flow concurrently in the pipelines, leading to a variety of complex flow patterns. However, the presence of acid gases such as CO2 and H2S soluble in the water can lead to internal corrosion attack if the water comes into contact with the mild steel pipe wall, a scenario known as 'water wetting'. In this experimental work, a large-scale 0.1 m ID inclinable flow loop was used to study the three-phase gas-oil-water flow in horizontal and vertical positions. A light model oil (�o = 823 kg/m3, μo= 2.7 cP), an aqueous 1 wt. NaCl solution and CO2 gas were utilized as the test fluids. Two measurement techniques: high speed video camera and flush mounted conductivity pins were employed for flow pattern visualization and surface wetting measurements, respectively. The flow patterns and surface wetting behaviors were quantified at various liquid velocities, gas velocities and water cuts up to 20. The flow patterns were classified according to the global gas-liquid structure and local oil-water distribution. The flow patterns were seen to change from stratified to intermittent and finally annularmist flows as the superficial gas velocity increased, while the local oil and water phases were either separated or dispersed. At low water cut, the wetting results showed that adding the gas phase can help to keep water away from the pipe wall, leading to oil wetting. At high water cut, water wetting prevailed and the flow of gas did not lessen the intensity of water wetting. © 2015 by Nace International.