A Simplified Model for Oil/Water Flow in Vertical and Deviated Wellbores

Abstract

Summary This paper presents the results of an experimental study and a semitheoretical analysis of two-phase oil/water flow in vertical and deviated systems. The study focuses on water-dominated flow regimes, where the patterns may be termed as bubbly flow, pseudoslug flow, and churn flow. A drift-flux approach is taken to analyze the flow behavior of oil/water systems. For the three flow regimes investigated, the drift velocity of the lighter oil phase is found to be dependent on its in-situ volume fraction in addition to the terminal bubble- or droplet-rise velocity. For flow in both vertical and deviated pipes, we were able to develop a single expression for the drift flux, uow, resulting in a single equation for the in-situ oil fraction, fo, for the three flow regimes studied. We correlated fo with the oil superficial velocity, vos, and the terminal rise velocity, vꝏθ, using the expression, fo=vos/{1.2vm + vꝏθ f(1 — fo)2}. In a deviated pipe, the terminal rise velocity, vꝏθ, is correlated with that in a vertical pipe by =vꝏ/'″ (cosθ)0.5(1 + sinθ)2, for θ <70°. The performance of the proposed method in estimating fo is in good agreement with our measurements. Published data further augment the approach presented here.