Effects of high oil viscosity on oil-gas downward flow in deviated pipes. Part 2: Holdup and pressure gradient

In Part 1 of this work, new experimental data on high viscosity oil-gas flow in inclined downward flow were presented. Flow patterns transitions were identified and analyzed, and the performance of some flow pattern prediction models was validated. This study uses the same experimental data set generated for a mixture of air-oil (with a viscosity of 213 mPa center dot s) flowing in a 50.8 mm internal diameter pipe with inclination angles of -45 degrees, -60 degrees, -70 degrees, -80 degrees, -85 degrees for a ranges 0.05 m/s-0.7 m/s and 0.7 m/s-7 m/s of superficial liquid and gas velocities, respectively, to investigate holdup and pressure gradient behaviour. The holdup and pressure recovery effects are explained in terms of the predominant transport mechanism through phase slippage and the mechanical energy balance. For a constant superficial liquid velocity, the average-liquid holdup results show a discernible behaviour dependent on the relative velocity between phases (slip velocity). Consistently, results show a switch between the gravity or shear forces transport mechanism, that coincides with the switch of a sign of the total pressure gradient (pressure recovery effect). Performance analysis of the available mechanistic models has been presented. The results are not satisfactory, which justifies the need for a detailed study of the effects of viscosity and the inclination of the pipe in liquid-gas mixtures.

Automated summary

This study investigates the holdup and pressure gradient behavior of high viscosity oil-gas flow in inclined downward flow, highlighting the transport mechanism through phase slippage and mechanical energy balance. Performance analysis of available mechanistic models reveals the need for a detailed study of the effects of viscosity and pipe inclination in liquid-gas mixtures.