A simple model for annular two-phase flow in wellbores

Annular flow is associated with production from both gas-condensate and geothermal wells. Oil wells also experience it during high-gas-to-oil-ratio (high-GOR) production. The current semimechanistic modeling approach requires estimation of film thickness before computing frictional pressure drop as gas flows past the wavy-liquid film surrounding the pipe wall. This study intends to investigate this film thickness and its impact on pressure-drop computation in wellbores producing steam-water, gas-condensate, and gas-oil mixtures. Computational results show that this dimensionless liquid-film thickness is most likely less than 0.06 in annular flow. For such values of thin-film thickness, the computed friction factor is only slightly higher than that estimated with a smooth-channel assumption. When the homogeneous model is used to compute pressure gradient by ignoring the wavy-liquid film on frictional pressure drop, good agreement is achieved with field data and with the predictions of a semimechanistic model. Copyright © 2007 Society of Petroleum Engineers.