Estimating frictional pressure drops of inclined two- and three-phase flows for subsea resource production

Gas-lift pumping is a potential approach for conveying subsea resources from the seafloor. Flow assurance is a critical issue because the internal flow of a gas-lift pumping system becomes a gas–liquid–solid three-phase flow. A key step for flow assurance is estimating the involved frictional pressure drop. Although previous studies have estimated the frictional pressure drop of vertical three-phase flows, correlations for inclined three-phase flows have not yet been established. Herein, first, the effects of pipe inclination on estimating velocities were investigated based on separated-flow models. We then conducted experiments on vertical and inclined two- and three-phase flows using pipes and glass beads as solid particles. We examined the calculated results to determine the effect of pipe inclination on the frictional pressure drop. Results showed that pipe inclination angle exhibited negligible influence on the interfacial-effect term of the involved separated-flow model. We developed two kinds of methods for estimating the frictional pressure drop of inclined three-phase flows, out of which the best-performing method demonstrated a strong correlation with the experimental results.