A comparison of numerical simulations with experimental and theoretical investigations of highly-viscous oil-aqueous foam horizontal flow

Abstract A possible innovative technology of foam injection for facilitating the transportation of heavy oils is explored. To this aim, a numerical study on flow characteristics of highly viscous oil flowing through a 25 mm i. d. horizontal pipe under the action of aqueous foam was conducted. The Volume of Fluid (VOF) multiphase flow modeling method embodied in ANSYS Fluent was applied to simulate the Newtonian oil/non-Newtonian foam two-phase flow. Simulations were conducted covering oil and foam superficial velocities of 0.1–0.9 m/s and 0.05–0.84 m/s, respectively, corresponding to the experimental range. Cross-sectional axial velocity profiles, oil volume fractions, phase - distribution and pressure gradients were extracted from the CFD simulations. The flow patterns were compared to actual images taken from a high-speed, high resolution camera. Pressure gradients, drag reduction ratios and oil-transport efficiencies were compared with the experimental data and mechanistic model predictions. Good agreement was achieved among the simulated, experimental and predicted data over a wide range of operational conditions. With the complete encapsulation of the oil core by the foam annulus, a critical foam fraction can be established to reach maximum drag reduction ratio. An optimum foam/oil flow rate ratio for the highest oil-transport operational coefficient was identified.