Experimental Study of Two-Phase Flow Patterns and Pressure Drop in Horizontal Pipelines Transporting Crude Oil and Gas Mixtures in Niger Delta Conditions

The accurate prediction of two-phase flow patterns and pressure drop in the multiphase production pipelines of the Niger Delta is essential for pipeline design, flow assurance management, and production optimisation, yet most available predictive correlations have been developed from laboratory data at conditions not representative of tropical African field operations. This study presents an experimental investigation of two-phase oil-gas flow patterns and pressure drop in a horizontal test pipeline of 50-millimetre internal diameter using a synthetic crude oil surrogate and nitrogen gas to represent conditions representative of Niger Delta wellhead production streams. Flow pattern maps were developed by systematically varying superficial liquid velocities from 0.2 to 2.0 metres per second and superficial gas velocities from 0.5 to 12 metres per second. High-speed camera visualisation and conductance probe signals were used to identify and classify flow regimes into stratified, stratified-wavy, slug, and annular patterns. Pressure gradient measurements were recorded at each flow condition using calibrated differential pressure transducers. Experimental flow pattern observations were compared against the predictions of three widely used flow pattern transition correlations. Experimental pressure drop data were compared against eight published empirical and mechanistic pressure drop models. Results showed that the Taitel and Dukler flow pattern model exhibited the best agreement with experimental observations, correctly predicting 78 percent of observed transitions. The Beggs and Brill pressure drop model provided the closest quantitative agreement with measured values. A modified pressure drop correlation accounting for tropical fluid viscosity conditions is proposed. Keywords: two-phase flow, flow pattern, pressure drop, multiphase pipeline, Niger Delta.