Characterization of oil-water flow patterns in vertical and deviated wells

An oil-water flow pattern classification and characterization for well bore s is proposed based on the integrated analysis of experimental data, includ ing frictional pressure drop, holdup, and spatial phase distribution, acqui red in a transparent test section (2-in. i.d., 51-ft long) using a refined mineral oil and water (rho(o)/rho(w)=0.85, mu(o)/mu(w)=20 01 and sigma(o-w) =33.5 dyn/cm at 90 degrees F). The tests covered inclination angles of 90 d egrees, 75 degrees, 60 degrees, and 45 degrees from horizontal. The oil-water dow patterns have been classified into two major categories g iven by the status of the continuous phase, including water-dominated flow patterns and oil-dominated flow patterns. It was found that most-water-domi nated flow patterns show significant slippage but relatively low frictional pressure gradients. In contrast, all the oil-dominated dow patterns exhibi t negligible slippage but significantly larger frictional pressure gradient s. Six flow patterns have been characterized in upward vertical flow; three were water dominated and three were oil dominated. In upward inclined flow there were four water-dominated how patterns, two oil-dominated flow patte rns and a transitional flow pattern. Flow-pattern maps for each of the test ed inclination angles are presented. A mechanistic model to predict flow-pa ttern transitions in vertical wells is proposed. The transitions to the ver y-fine-dispersed flow patterns were evaluated by combining the concepts of turbulent kinetic energy with the surface free energy of the droplets, whil e the transitions to the churn how pattern and the phase inversion were pre dicted based on the concept of agglomeration. The model compares favorably with the measured data.