Characterisation and simulation of bidirectional multiphase flow in tubes

Abstract

The bidirectional flow reversal phenomenon results in liquid accumulation, causes significant increase in pressure drop and therefore, the pumping power. In pipelines, this poses significant problem due to the presence of slug to churn, especially in producing gas wells. To understand the bidirectional flow reversal phenomena of co-current to counter-current annular flow with a falling liquid film inside a vertical tube with internal diameter of 0.054 m, height of 10.5m length, and length of 40m horizontal section, was researched experimentally. Despite the significance of this problem, there is lack of reports in the literature of a generally accepted empirical correlation model that resolves the phenomenon of flow reversal and flooding in vertical tubes for gas / liquid flows with different fluids. Rather, experimental empirical model correlation developed so far relied on air/water flows. This research, therefore, has studied flow reversal phenomenon, using gas, light viscous oil, and water as working fluids, to compare experimentally obtained flow reversal, flooding superficial gas and liquid velocity conditions with existing works, established flow reversal and flooding correlations, in addition, CFD Ansys simulation to carry out experimental data analysis and reviewed methodologies that focus on the churn/annular-annular mist flow regimes transition explored by other researchers. The outcome was a valid empirical model that correlates flow reversal and flooding within the geometry under study and have establish a critical superficial gas velocity of 3.5 m/s to avoid a bidirectional flow in gas wells. Also achieved, was a programmed, flow regime recognition in two-phase flow reversal and flooding in tubes. The empirical model correlation curve and the critical superficial gas flow rate of 3.5 m/s derived in this work will enable oil and gas well engineers to establish whether a specific well has enough flow velocity to lift both gas and water sufficiently to the surface without flow reversal and resulting in liquid accumulation in a producing well. Further research is recommended to study the effect of fluid properties especially density and viscosity and liquid film thickness on the flow reversal and flooding phenomena.