Effects of surface wettability on the prediction of phase wetting transition boundary in horizontal oil pipelines with produced water

Purpose Water wetting, caused by produced water in crude oil, is a major contributor to internal corrosion in steel pipelines. This study aims to investigate the effects of surface prewetting on the wettability of X65 carbon steel under oil–water two-phase flow conditions. Design/methodology/approach Comparative experiments were conducted with hydrophilic and hydrophobic surfaces, evaluating wettability alterations through dispersed droplet size distribution and phase wetting mapping. A predictive model for phase wetting transition boundaries was developed, incorporating the effects of surface wettability and dynamic flow conditions. Findings Results revealed that hydrophobic surfaces, prewetted with crude oil, significantly reduced water layer thickness, whereas hydrophilic surfaces exhibited persistent water accumulation even at high velocities. The proposed model was validated by experimental data and demonstrated superior accuracy in calculating maximum droplet diameters and identifying phase transition boundaries compared to conventional models. It also highlighted the role of water droplet re-entrainment in maintaining oil-wetted surfaces on hydrophobic pipes. Originality/value The experiment and the proposed model underscore the mechanism of surface wettability in the prediction of corrosion-prone areas in advance in oil pipelines, especially in low water cut area. It can also help to evaluate the pipeline integrity without shutting down the transportation for corrosion detection, especially for the pipeline underground.