An improved version of drift-flux model for predicting pressure-gradient and void-fraction in vertical and near vertical slug flow

• An alternative approach to modelling slug flow was proposed.
• The approach was based on the inherent mechanisms of slug flow.
• The contribution of these mechanisms was considered at various angles.
• A unified form of void-fraction expression for slug flow pattern was developed.
• Void fraction of slug flow at vertical and deviated angles was considered.

Slug flow research has received continuous and strong attention by many investigators for many years and various predictive models have been developed for calculating slug hydrodynamics. Some researchers relied on experimental data correlation while some modelled the slug flow to simulate the behaviour sufficiently accurately to estimate pressure drops. Because slug flow is the most common flow in producing wells, this leads to the pressure drop being underestimated/overestimated significantly. The intent of this study is to present an alternative approach to modelling slug flow. The proposed model considered wall shear stress in the liquid slug zone and the wall shear stress in the film zone in estimating the pressure drop in slug flow which have been neglected in most literatures. The proposed models are compared with published data from diverse sources and agree well with the experimental data.